assignment on negative effects of population growth

Advantages and disadvantages of population growth

Over the course of history, the world has seen rapid population growth. It has enabled a rich diversity of culture, technology and improved living standards. However, population growth is increasingly coming at a cost – in particular to the environment. High population levels are contributing to the depletion of natural resources and causing widespread pollution. Some fear population growth is now deeply damaging for both the planet and even the survival of many natural habitats. However, others argue that fears other population growth are misplaced with the planet having room for more people, so long as we learn to live more in harmony with nature and more efficiently in big cities.

Advantages of population growth

1. More people leads to greater human capital . If there are more people, the probability of finding a genius like Einsterin, Marie Curie, Beethoven increase. These exceptional people can lead to technological and cultural masterpieces which enrich our lives. The past 200 years have shown exponential growth in technical development and innovation. There are many factors behind this, but the world’s growing population means we have a bigger pool of human capital and the possibility of these cutting edge discoveries increase.

2. Higher economic growth . Population growth will lead to economic growth with more people able to produce more goods. It will lead to higher tax revenues which can be spent on public goods, such as health care and environmental projects.

• The obvious evaluation is to say, the crucial thing is not GDP, but GDP per capita . If economic growth is at the same rate as population growth, average living standards will not increase. However, it is possible population growth can also improve per capita incomes. As the population increases, the economy can benefit from a bigger talent pool, economies of scale and greater specialisation. All this can enable higher per capita income, which we have seen in major developed economies.

3. Economies of scale . Farming and industry have been able to benefit from economies of scale, which means as the population grows, food output and manufacturing output have been able to grow even faster than population growth. For example, at the turn of the nineteenth century, Thomas Malthus predicted population growth would lead to famine as we would be unable to feed the growing population. However, his dire predictions failed to materialise because he failed to understand, that the productivity of land, labour and capital could all increase more than proportionately. 300 years ago, most of the population worked on the land. Technological innovation and economies of scale , mean productivity of land has vastly increased as farmers make use of mechanisation and economies of scale for increased food production.

4. The efficiency of higher population density . In terms of per capita carbon footprint, areas with a high population density are significantly more efficient than rural areas and places with a low population. When people live in densely populated areas, they are more likely to use public transport, live in apartment buildings which are easier to heat. In big cities, transport and the delivery of goods is much more efficient, whereas for low population densities, the average cost and environmental footprint are much higher.  Therefore, population growth which leads to growth in city connurbations (which is a feature of global growth in past) is not as environmentally damaging as we may think. In Green Metropolis , by David Owen he argues living in closer proximity in cities is a key aspect of sustainability

• Urban areas account for only 3% of the world’s land surface. But, more than 50% of the population. By 2050, the United Nations predict this will rise to 70%. Therefore, population growth doesn’t have to lead to an equivalent fall in natural habitats.

5. The improved demographic structure of society. Many western economies are now experiencing a falling population, with the result that their population demographic is being skewed to old, retired people. This is imposing costs on society as we struggle to pay for health care and pensions. Moderate population growth helps to rebalance the population with a higher share of young, working people.

6. Critical mass . Higher populations can enable a critical mass of people to enable a sider, more vibrant society. With low populations, there is less scope for diversity. But, when the population grows, it can enable the support of a broader cultural range of activities.

Disadvantages of population growth

1. Cost to the environment. Population growth exacerbates many of the existing environmental problems

• Trying to reduce carbon and methane emissions to reduce global warming is relatively more difficult as the population.
• There will be greater threat on natural habitats as a greater population has greater demand for housing and farmland. This will increase pressure to cut down forests to make way for farming and housing.
• Higher population will lead to a greater consumption of non-renewable resources, leading to a faster depletion of natural resources.
• Higher population will lead to greater pollution levels in air, water and land. Higher pollution is associated with a range of health issues, such as cancer and asthma. The pollution also harms animals and plants.
• Soil degradation. To feed a growing planet, we have seen serious degrading of farmland (according to UN estimates) about 12 million hectares of farmland every year. This is due to factors, such as overgrazing, use of chemicals, climate change and use of chemicals.

2. Congestion . Too many people in a small space will lead to various types of congestion. Road congestion is a major problem across the world. One study suggested congestion cost the EU €111bn (1% of GDP) in 2012. WIth population growth, the costs of congestion will only increase leading to time lost, more pollution and lost output.

3. Water shortages . Already up to 40% of the world’s population face water scarcity and the risk of drought. According to  the UN water shortages could lead to 700 million people at the risk of displacement. A growing population will put pressure on scarce water supplies and this is a factor behind many minor and major conflicts with countries having to find ways around the shortage of water.

4. Generating unsustainable waste . We are currently generating non-biodegradable rubbish that we are struggling to process. It tends to end in landfill, causing methane emissions and other toxic problems.

• Factors that affect population size and growth
• Impact of rising population in the UK

14 thoughts on “Advantages and disadvantages of population growth”

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I enjoyed reading your article on the pros and cons of population growth. It was well-written and informative.

I agree with your points about the potential benefits of population growth, such as increased economic growth and innovation. However, I also think it’s important to be aware of the potential challenges, such as increased pressure on resources and the environment.

I think it’s important to find a balance between the benefits and challenges of population growth. We need to find ways to ensure that population growth is sustainable and that it doesn’t lead to negative consequences for the environment or society.

For more information on population growth, I recommend checking out Exam Notes. The website has a wealth of information on the topic, including articles, blog posts, and videos.

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Comments are closed.

Understanding Global Change

Discover why the climate and environment changes, your place in the Earth system, and paths to a resilient future.

Population growth

Population growth is the increase in the number of humans on Earth. For most of human history our population size was relatively stable. But with innovation and industrialization, energy, food , water , and medical care became more available and reliable. Consequently, global human population rapidly increased, and continues to do so, with dramatic impacts on global climate and ecosystems. We will need technological and social innovation to help us support the world’s population as we adapt to and mitigate climate and environmental changes.

World human population growth from 10,000 BC to 2019 AD. Data from: The United Nations

Human population growth impacts the Earth system in a variety of ways, including:

• Increasing the extraction of resources from the environment. These resources include fossil fuels (oil, gas, and coal), minerals, trees , water , and wildlife , especially in the oceans. The process of removing resources, in turn, often releases pollutants and waste that reduce air and water quality , and harm the health of humans and other species.
• Increasing the burning of fossil fuels for energy to generate electricity, and to power transportation (for example, cars and planes) and industrial processes.
• Increase in freshwater use for drinking, agriculture , recreation, and industrial processes. Freshwater is extracted from lakes, rivers, the ground, and man-made reservoirs.
• Increasing ecological impacts on environments. Forests and other habitats are disturbed or destroyed to construct urban areas including the construction of homes, businesses, and roads to accommodate growing populations. Additionally, as populations increase, more land is used for agricultural activities to grow crops and support livestock. This, in turn, can decrease species populations , geographic ranges , biodiversity , and alter interactions among organisms.
• Increasing fishing and hunting , which reduces species populations of the exploited species. Fishing and hunting can also indirectly increase numbers of species that are not fished or hunted if more resources become available for the species that remain in the ecosystem.
• Increasing the transport of invasive species , either intentionally or by accident, as people travel and import and export supplies. Urbanization also creates disturbed environments where invasive species often thrive and outcompete native species. For example, many invasive plant species thrive along strips of land next to roads and highways.
• The transmission of diseases . Humans living in densely populated areas can rapidly spread diseases within and among populations. Additionally, because transportation has become easier and more frequent, diseases can spread quickly to new regions.

Can you think of additional cause and effect relationships between human population growth and other parts of the Earth system?

Visit the burning of fossil fuels , agricultural activities , and urbanization pages to learn more about how processes and phenomena related to the size and distribution of human populations affect global climate and ecosystems.

Investigate

Learn more in these real-world examples, and challenge yourself to  construct a model  that explains the Earth system relationships.

• The Ecology of Human Populations: Thomas Malthus
• A Pleistocene Puzzle: Extinction in South America

Links to Learn More

• United Nations World Population Maps
• Scientific American: Does Population Growth Impact Climate Change?

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What Are Environmental Problems Due to Population Growth?

The Effects of Human Intervention on the Environment

It’s no secret that the planet faces serious environmental concerns from water and air pollution to deforestation. While the causes are complex, one significant contributor to the problem is population growth. Understanding the relationship between population growth and environmental issues may be the first step toward identifying real solutions.

TL;DR (Too Long; Didn't Read)

Population growth is the increase in the number of people living in a particular area. Since populations can grow exponentially, resource depletion can occur rapidly, leading to specific environmental concerns such as global warming, deforestation and decreasing biodiversity. Populations in developed countries trend toward using substantially more resources, while populations in developing countries feel the impacts of environmental problems more quickly.

How Population Growth Works

The concept of population growth is tricky because populations can grow exponentially – similar to the way a bank or credit card company compounds interest. The formula for exponential population growth is N=N 0 e rt where N 0 is the starting population, e is a logarithmic constant (2.71828), r is the rate of growth (birth rate minus death rate), and t is time. If you plot this equation, you see a curve arching upward over time as the population increases exponentially, assuming no change in the rate.

This concept might be easier to visualize with actual figures. From the beginning of time on Earth to the start of the 20th century, the population of the planet grew from zero to 1.6 billion. Then, thanks to many factors, the population increased to 6.1 billion in just 100 years, which is an almost fourfold increase in the number of humans over a relatively short period.

Populations and Environmental Issues

More people require more resources, which means that as the population increases, the Earth’s resources deplete more rapidly. The result of this depletion is deforestation and loss of biodiversity as humans strip the Earth of resources to accommodate rising population numbers. Population growth also results in increased greenhouse gases, mostly from CO 2 emissions. For visualization, during that same 20th century that saw fourfold population growth, CO 2 emissions increased twelvefold. As greenhouse gases increase, so do climate patterns, ultimately resulting in the long-term pattern called climate change.

The Biggest Impacts

The use of resources and the impact of environmental issues are not equal around the globe. People in developed countries require substantially more resources to maintain their lifestyles compared with people in developing countries. For example, the United States, which contains 5 percent of the world’s population, currently produces a full 25 percent of CO 2 emissions.

People in developing countries tend to feel the impacts of environmental problems more acutely, especially if they live in coastal areas directly affected by sea level rise and the extreme weather events that accompany climate change. The most vulnerable populations also experience decreased access to clean water, increased exposure to air pollution and diseases – which may result from decreased biodiversity – and may feel the impact more immediately as local resources including plants and animals deplete.

While the interconnected problems of population growth and environmental issues seem overwhelming, it is important to remember that humans can make changes that positively impact the planet. One good starting point is understanding and applying the concept of sustainability, which is the opposite of resource depletion. Sustainability describes a model of resource usage in which the current generation uses only the resources the Earth provides indefinitely (like solar or wind power instead of burning fossil fuels) to ensure that future generations inherit resources.

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• Scientific American: Does Population Growth Impact Climate Change?
• World Health Organization: Environment and Health in Developing Countries

About the Author

Melissa Mayer is an eclectic science writer with experience in the fields of molecular biology, proteomics, genomics, microbiology, biobanking and food science. In the niche of science and medical writing, her work includes five years with Thermo Scientific (Accelerating Science blogs), SomaLogic, Mental Floss, the Society for Neuroscience and Healthline. She has also served as interim associate editor for a glossy trade magazine read by pathologists, Clinical Lab Products, and wrote a non-fiction YA book (Coping with Date Rape and Acquaintance Rape). She has two books forthcoming covering the neuroscience of mental health.

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The Effect of Population Growth on the Environment: Evidence from European Regions

• Published: 09 April 2018
• Volume 35 , pages 379–402, ( 2019 )

Cite this article

• Hannes Weber   ORCID: orcid.org/0000-0002-1163-9219 1 &
• Jennifer Dabbs Sciubba 2  

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There is a long-standing dispute on the extent to which population growth causes environmental degradation. Most studies on this link have so far analyzed cross-country data, finding contradictory results. However, these country-level analyses suffer from the high level of dissimilarity between world regions and strong collinearity of population growth, income, and other factors. We argue that regional-level analyses can provide more robust evidence, isolating the population effect from national particularities such as policies or culture. We compile a dataset of 1062 regions within 22 European countries and analyze the effect from population growth on carbon dioxide (CO 2 ) emissions and urban land use change between 1990 and 2006. Data are analyzed using panel regressions, spatial econometric models, and propensity score matching where regions with high population growth are matched to otherwise highly similar regions exhibiting significantly less growth. We find a considerable effect from regional population growth on carbon dioxide (CO 2 ) emissions and urban land use increase in Western Europe. By contrast, in the new member states in the East, other factors appear more important.

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Note Thick black lines denote the median, box limits are 25th and 75th percentile, respectively, red marks are mean values, and jitter points are regions ( N = 96 in high population growth group and N = 96 in control group). (Color figure online)

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Population, immigration, and air quality in the USA: a spatial panel study

The (de-) carbonization of urbanization, 1960–2010.

The EU classifies its territory into four layers according to the Nomenclature des Unités Territoriales Statistiques (NUTS). The lowest level consists of NUTS-3 regions, designed to usually host between 150,000 and 800,000 people. France, for instance, consists of 100 NUTS-3 regions (départements), 20 NUTS-2 regions (régions), 8 NUTS-1 regions (groups of régions), and one NUTS-0 region (metropolitan France).

These countries are Austria, Belgium, Bulgaria, Croatia, Czech Republic, Denmark, Estonia, France, Germany, Hungary, Italy, Ireland, Latvia, Lithuania, Luxembourg, Netherlands, Poland, Portugal, Romania, Slovakia, Slovenia, and Spain. For CO 2 emissions, no data were available for Croatia. As a result of a reform of regional boundaries in the German state of Saxony, most regions in Saxony are missing from the analysis (note the white area on the maps).

For the models explaining urban growth which is measured between 1990 and 2006, population growth is averaged for this period. However, population data are not available for all regions since 1990 in the source dataset; for these regions the values refer to average population growth between the earliest available year since 1990 and 2008. Figure  1 displays average annual population growth rates between 2000 and 2008 for all regions.

Since urban land use is measured as a percentage of total land use and therefore 0–1 bounded, we use the logit transformation on this variable.

A random effects model was initially considered (providing similar results to the fixed effects model), but a Hausman test suggested superiority of the fixed effects estimator. Since we are not interested in estimating country-level predictors, we went without random effects (or multilevel) models.

Optimal matching and genetic matching were used as alternative algorithms. Since the results do not differ substantially, we only report the findings from propensity score matching here.

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Weber, H., Sciubba, J.D. The Effect of Population Growth on the Environment: Evidence from European Regions. Eur J Population 35 , 379–402 (2019). https://doi.org/10.1007/s10680-018-9486-0

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July 29, 2009

Does Population Growth Impact Climate Change?

Does the rate at which people are reproducing need to be controlled to save the environment?

Dear EarthTalk : To what extent does human population growth impact global warming, and what can be done about it? -- Larry LeDoux, Honolulu, HI

No doubt human population growth is a major contributor to global warming, given that humans use fossil fuels to power their increasingly mechanized lifestyles. More people means more demand for oil, gas, coal and other fuels mined or drilled from below the Earth’s surface that, when burned, spew enough carbon dioxide (CO2) into the atmosphere to trap warm air inside like a greenhouse.

According to the United Nations Population Fund, human population grew from 1.6 billion to 6.1 billion people during the course of the 20th century. (Think about it: It took all of time for population to reach 1.6 billion; then it shot to 6.1 billion over just 100 years.) During that time emissions of CO2, the leading greenhouse gas, grew 12-fold. And with worldwide population expected to surpass nine billion over the next 50 years, environmentalists and others are worried about the ability of the planet to withstand the added load of greenhouse gases entering the atmosphere and wreaking havoc on ecosystems down below.

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Developed countries consume the lion’s share of fossil fuels. The United States, for example, contains just five percent of world population, yet contributes a quarter of total CO2 output. But while population growth is stagnant or dropping in most developed countries (except for the U.S., due to immigration), it is rising rapidly in quickly industrializing developing nations. According to the United Nations Population Fund, fast-growing developing countries (like China and India) will contribute more than half of global CO2 emissions by 2050, leading some to wonder if all of the efforts being made to curb U.S. emissions will be erased by other countries’ adoption of our long held over-consumptive ways.

“Population, global warming and consumption patterns are inextricably linked in their collective global environmental impact,” reports the Global Population and Environment Program at the non-profit Sierra Club. “As developing countries’ contribution to global emissions grows, population size and growth rates will become significant factors in magnifying the impacts of global warming.”

According to the Worldwatch Institute, a nonprofit environmental think tank, the overriding challenges facing our global civilization are to curtail climate change and slow population growth. “Success on these two fronts would make other challenges, such as reversing the deforestation of Earth, stabilizing water tables, and protecting plant and animal diversity, much more manageable,” reports the group. “If we cannot stabilize climate and we cannot stabilize population, there is not an ecosystem on Earth that we can save.”

Many population experts believe the answer lies in improving the health of women and children in developing nations. By reducing poverty and infant mortality, increasing women’s and girls’ access to basic human rights (health care, education, economic opportunity), educating women about birth control options and ensuring access to voluntary family planning services, women will choose to limit family size.

CONTACTS : United Nations Population Fund, www.unfpa.org; Sierra Club’s Global Population and Environment Program, www.sierraclub.org/population; Worldwatch Institute, www.worldwatch.org.

EarthTalk is produced by E/The Environmental Magazine. SEND YOUR ENVIRONMENTAL QUESTIONS TO: EarthTalk , P.O. Box 5098, Westport, CT 06881; [email protected] . Read past columns at: www.emagazine.com/earthtalk/archives.php . EarthTalk is now a book! Details and order information at: www.emagazine.com/earthtalkbook .

The Connections Between Population and Climate Change Info Brief

Climate change is one of humanity’s most critical challenges. The warming of the planet threatens food security, freshwater supply, and human health. The effects of climate change, including sea level rise, droughts, floods, and extreme weather, will be more severe if actions are not taken to dramatically reduce emissions of greenhouse gases into the atmosphere [1] . While the link between human action and the planet’s recent warming remains an almost unanimous scientific consensus, the links between population growth and climate change deserve further exploration [2] .

In 2023, the global population surpassed 8 billion. With 1 billion people projected to be added to our human ranks by 2040 and an additional 1 billion more by 2060, demographic trends and variables play an important role in understanding and confronting the world’s climate crisis [3] . Population growth, along with increasing consumption, tends to increase emissions of climate-changing greenhouse gases. Rapid population growth worsens the impacts of climate change by straining resources. It also exposes more people to climate-related risks [4-8] .

Including population dynamics in climate change-related education and advocacy can help clarify why improving access to reproductive health care, family planning options, girls’ education, and gender equity are important climate mitigation strategies. Increased investment in health and education, along with improvements in infrastructure and land use, would strengthen climate resilience and build adaptive capacity for people around the world [5, 9, 10] .

EARTH’S TEMPERATURE IS RISING

Earth’s average temperature is higher than at any point in recorded history, with new temperature records now being set on a regular basis [11] . The Intergovernmental Panel on Climate Change (IPCC) estimates that human emissions of greenhouse gases, including carbon dioxide (CO 2 ), methane, and nitrous oxide, have raised the global average temperature by 1.1°C (2°F) above pre-industrial levels [12] .

To limit the risks posed by climate change, countries around the world agreed to hold the average temperature increase well below 2°C, aiming for a 1.5°C threshold [13] . If current warming trends continue, the Earth’s average temperature increase is likely to reach 1.5°C by the 2030s [1, 14] . Global warming above this level would significantly increase the risk and frequency of extreme weather events and damage to many of the planet’s terrestrial and marine ecosystems [12] .

Holding the temperature rise to 1.5°C involves fundamentally changing the processes that produce the most greenhouse gas emissions, especially burning fossil fuels for energy, industry, and transportation. A global energy transition involving using energy more efficiently, generating it from renewable sources, such as solar and wind, and electrifying transportation would reduce emissions from coal, oil, and natural gas. This is especially relevant for high polluting areas such as the United States, Europe, China, and India [15] . Stopping forest loss, planting new forests, reducing food waste, and managing land to conserve soil carbon also are additional important steps to limit warming for both the industrial and developing countries.

POPULATION AND EMISSIONS LINKS

There has been a reluctance to integrate discussions of population into climate education and advocacy. Yet climate change is tightly linked to population growth. As the U.K.-based charity Population Matters summarizes: “Every additional person increases carbon emissions—the rich far more than the poor—and increases the number of climate change victims—the poor far more than the rich” [16] . At the national level, there is a clear relationship between income and per capita CO 2 emissions, with average emissions for people living in industrialized countries and key oil producing nations topping the charts [17] . Consumerist lifestyles and polluting production practices in the highest-income countries result in much higher emissions rates than in middle- and low-income countries, where the majority of the world’s population lives (Figures 1 and 2) [3, 18-22] .

For example, the United States represents just over 4% of the global population but accounts for 17% of the world’s energy use [3, 23] . Per person carbon emissions in the U.S. are among the highest in the world. People living in the United States, Australia, and Canada have carbon footprints close to 200 times larger than people in some of the poorest and fastest-growing countries in sub-Saharan Africa, such as Chad, Niger, and the Central African Republic [17] . In the middle of the spectrum are the middle-income economies, home to 75% of the world’s population [24] . In these places, industrialization likely will increase standards of living and consumption patterns over the coming decades [25, 26] . Without changes to how economies tend to grow—namely by decoupling rising affluence with carbon emissions—their contribution to global warming will rise.

As there is no panacea for climate change mitigation, a wide variety of options needs to be exercised. An integrated approach includes educating girls and empowering women to make their own decisions about reproduction [27] .

FIGURE 1. GLOBAL POPULATION BY INCOME LEVEL, 1950-2021

FIGURE 2. CARBON DIOXIDE EMISSIONS BY INCOME LEVEL, 1950-2021

Examining the effects of different population growth rates on future economic growth and energy use shows that slowing population growth can significantly reduce future greenhouse gas emissions [4, 6, 7] . Incorporating various population projections into climate models shows that higher population growth typically results in higher emissions. For example, one study found that if the global population were to peak in mid-century and then shrink to 7.1 billion by 2100, carbon emissions could be as much as 41% lower than if the population continued to grow to 15 billion [28] .

Even in scenarios of low population growth, however, carbon-intensive economic growth and technological choices can result in high emissions [9] . Nevertheless, a growing body of research indicates that slowing global population growth through rights-based measures, such as by increasing access to voluntary family planning services, can play a key role in mitigating climate change [4-7, 18, 28-30] .

POPULATION AND CLIMATE VULNERABILITY

Despite contributing very little to overall emissions, people living in some of the world’s most impoverished regions are in a position to bear the brunt of climate change’s most disastrous impacts. High rates of poverty and social inequality leave many low-income populations vulnerable to the weather extremes, water stresses, and food production challenges associated with a warming climate [31] . This vulnerability can be affected by factors like urbanization, geography, land use, infrastructure, and access to capital [32] . The combination of climate change impacts and rapid population growth to regions already dealing with poverty and gender inequalities presents a humanitarian problem that will only continue to worsen if left unaddressed.

Low levels of education, gender inequality, and a significant unmet need for family planning information and services together lead to high levels of unplanned pregnancies. Globally, close to half of pregnancies are unintended [33] . In low- and middle-income countries alone, some 218 million women want to avoid pregnancy but are not using any form of modern contraceptives [34] .

Population pressures pose challenges for the environment and for economic development, undermining food security, poverty alleviation, natural resource conservation, and human health prospects. The UN’s medium variant projection shows that the global population could grow to 8.5 billion in 2030, 9.7 billion in 2050, and 10.3 billion in 2100 [3] . The fastest growth occurs among the 46 Least Developed Countries (LDCs), many of which are projected to double in population by mid-century [35] .

Under the UN Framework Convention on Climate Change, LDC governments can assess their vulnerability to climate change with the intention of identifying needs and appropriate actions in National Adaptation Programmes of Action [36] . The vast majority of these plans recognize rapid population growth as a key factor worsening climate vulnerability [36, 37] .

The links between population growth and climate vulnerability are visible around the world. In Pakistan, population pressures have led to land clearing, which exacerbates flooding at the same time that more people have been crowded into flood-prone areas [38, 39] . In Afghanistan, multi-year droughts have compounded the ongoing stresses of conflict and economic collapse, forcing millions of people from their homes [40, 41] .

FIGURE 3. PROJECTED POPULATION CHANGE IN SELECTED COUNTRIES MOST THREATENED BY CLIMATE CHANGE IMPACTS, 2023-2100

Sub-Saharan Africa is expected to double in population by 2050—accounting for half the world’s population growth [3] . The region is home to many of the countries most threatened by the impacts of climate change [42] . People in Niger, the Democratic Republic of the Congo, Mali, Somalia, and Chad are among those facing more frequent droughts, severe floods, extreme heat, and soil erosion, all amidst rapidly growing populations (Figure 3) [3, 42] . In Malawi, where 95% of agriculture is rainfed, severe droughts and floods hamper food production [43-45] . Climate change is expected to deliver more extreme weather events there, including both flooding and droughts. [45]

An extreme example can be found in sub-Saharan Africa’s Sahel region (Figure 4), where tens of millions of people already face food insecurity [46] . The Sahel population grew from 31 million in 1950 to 100 million in 2013. Projections show it reaching 300 million by 2050 and more than 600 million by 2100 [47] . Temperatures in the Sahel are rising 1.5 times faster than the global average [48] . Scientists project a temperature increase of 3–5°C by mid-century and by as much as 8°C by 2100 (Figure 5) [47] . As a result, increasingly frequent droughts and floods threaten to further impair food production in a region where over 80% of farmland is already degraded and growing populations are shrinking the pastureland available to each family [48, 49] . Hundreds of millions of people could lack sustainable food supplies in future decades.

FIGURE 4. THE SAHEL REGION, FIGURE 5. TEMPERATURE AND POPULATION IN SAHEL

Around the globe, climate change is increasing the variability of precipitation patterns, making water management more difficult [49] . High population growth rates compound the challenge as they shrink water supplies available per person. Water withdrawals from rivers and underground sources can outpace natural replenishment.

Currently, people in 25 countries, totaling a quarter of the world’s population, live with extremely high water stress [50, 51] . Many are in the Middle East and North Africa, where annual average population growth of 1.5% is nearly double the global average rate of 0.8% [19, 50] . In India, the world’s most populous country, water shortages pose a significant threat to the country’s 1.4 billion inhabitants. India encompasses nearly 18% of the global population but holds less than 4% of the world’s freshwater resources [3, 19, 52] . Agriculture in the densely populated country is heavily dependent on irrigation; however, rivers have been diverted and wells have been overdrawn to meet the food and water needs of the growing population. Groundwater depletion or contamination affects more than half of Indian districts, and underground water levels are falling by between 1-3 meters a year in key food producing states [52, 53] . As climate change alters the patterns of the monsoon rains and the frequency of droughts, tens of millions of people could be forced to migrate in search of fresh water [54-56] .

While a warmer world will experience more water scarcity in some regions, flooding is also a threat, both inland and along coastlines, which also face rising sea levels and increased storm surge. Many of the world’s floodplains and coastlines are densely populated. Low-elevation coastal zones represent 2% of the world’s land area but contain well over 10% of the world’s population [57] . Of the world’s 31 megacities, 21 are along a coastline, and migration to the coasts is increasing [58] . As coastal and riverine populations grow, more people are at risk [5] . The World Resources Institute projects that the number of people affected by flooding will double between 2010 and 2030 [59] .

UNMET NEED FOR FAMILY PLANNING

Population growth is seen as a potential barrier to meeting the UN’s Sustainable Development Goals for 2030 [60] . These goals include ending poverty and hunger, ensuring access to clean water, achieving global gender equality, educating all children, stopping biodiversity loss and ecosystem destruction, and combating climate change. Rapid population growth stifles development by increasing hunger rates, resource use, greenhouse gas emissions, and species extinction [61, 62] .

Human-rights-based policies that empower women, educate all children, and address unmet needs for reproductive health services in all regions of the world would reduce population growth rates through voluntary reductions in fertility. These changes, in effect, would help avoid future climate-changing emissions while fostering sustainable development and increasing capacity for communities to adapt to climate change impacts [5] .

A woman’s ability to choose whether and when to bear children, as well as how many children to have over the course of her lifetime, is a basic human right. Empowering women can lead to poverty reduction and foster sustainable development [63] . It also creates a more equitable society over time. When people, in particular women and girls, gain access to education, they also gain political, economic, and social power. This facilitates economic growth, improves health and livelihoods, and delivers higher levels of bodily autonomy [64] . Women who are educated tend to have fewer children, and those that they bear are healthier [65, 66] . As individuals, families, and communities access higher levels of education and quality health care, these tools are passed onto subsequent generations [67] . Thus, the benefits of health and education compound over time [68] . Within the context of climate change, the additional health, education, and economic benefits afforded through family planning would greatly reduce climate vulnerability and increase resilience for women and families across the world.

Many of the same regions of the world with high rates of poverty and pronounced vulnerability to the impacts of climate change also have high levels of gender inequality, where many women experience relatively low levels of reproductive health, education, empowerment, and participation in the labor market (Figure 6) [42, 69, 70] . Contraceptive availability and use tend to be limited. In much of the Sahel region, for example, fewer than 10% of women are using modern contraception [19, 47] . While surveys indicate that only 10% of Niger’s married women of reproductive age use modern contraceptives, about 20% have expressed an unmet need for family planning [19, 71] . Family size averages close to 7 children [3] . Nearly 45% of girls of primary school age do not attend school [72] .

FIGURE 6. CLIMATE CHANGE VULNERABILITY AND GENDER INEQUALITY

In the face of very real threats that a changing climate poses to food security, increasing access to voluntary family planning services and education can lower fertility rates and reduce pressures on food and water supplies, helping to better ensure that children do not go hungry. The UN medium projection showing the global population reaching 9.7 billion by 2050 assumes a fertility decline for countries where large families are still prevalent [35] . Without investments in family planning and the removal of barriers preventing people from accessing reproductive health care and schooling, the global population could grow much faster and climate resilience could be weakened.

INVESTING IN WOMEN AS A LOW COST CLIMATE SOLUTION

Global greenhouse gas emissions averaged a record 54 gigatons of CO 2 -equivalent per year between 2010 and 2019, over two-thirds of which came from fossil fuel burning. Keeping the global average temperature from exceeding 1.5°C in a cost-effective manner would require reducing global emissions by 45% by 2030 [73] .

Research examining the potential impacts of increased investment in family planning found that funding family planning and girls’ education could prevent a cumulative 69 gigatons of CO 2 emissions between 2021 and 2050 [74] . That scale of reduction is similar to what could be achieved by shutting down some 18,000 coal-fired power plants [75] .

Family planning options could be provided in low-income countries at an annual cost of only around $10 per user [34] . The cost of avoiding emissions through investments in family planning comes out to about $4.50 per ton of CO 2 [76] . Educating girls yields emissions reductions at close to $10 per ton of CO 2 [77] . Both are cheaper than some other attractive emissions reduction options, such as wind and solar power (each less than $20 per ton), and represent a small fraction of outfitting new coal plants with carbon capture and storage technology (upwards of $95 per ton) [74, 76] . Investing in family planning and education is an incredibly cost-effective climate change solution—both in terms of upfront cost and return on investment. Fully meeting unmet needs for family planning worldwide could yield long-term health and economic benefits equal to $120 for each dollar spent on family planning [78] .

The annual funding gap for meeting family planning needs worldwide is just under $6 billion [79] . Family planning programs receive well under 1% of international development aid [80, 81] . Increasing spending to fill the unmet need for family planning services will help improve lives and mitigate climate change. In addition, healthy and educated populations will be better equipped to weather the effects of climate change [82] . This much is clear: Efforts to address climate change must include increasing access to reproductive health care services, education, and family planning options.

“Honoring the dignity of women and children through family planning is not about governments forcing the birth rate down (or up, through natalist policies). Nor is it about those in rich countries, where emissions are highest, telling people elsewhere to stop having children. When family planning focuses on health care provision and meeting women’s expressed needs, empowerment, equality, and well-being are the result; the benefits to the planet are side effects.” – Drawdown: The Most Comprehensive Plan Ever Proposed to Reverse Global Warming (2017)

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• World Food Programme. Food insecurity and malnutrition in West and Central Africa at 10-year high as crisis spreads to coastal countries. 2023; Available from: https://www.wfp.org/news/food-insecurity-and-malnutrition-west-and-central-africa-10-year-high-crisis-spreads-coastal.
• Potts, M., et al., Crisis in the Sahel: Possible solutions and the consequences of inaction. A report following the OASIS Conference (Organizing to Advance Solutions in the Sahel) hosted by the University of California, Berkeley and African Institute for Development Policy on September 21, 2012. 2013: http://oasisinitiative.berkeley.edu/publications/2016/2/20/crisis-in-the-sahel-possible-solutions-and-the-consequences-of-inaction.
• Muggah, R. and J. Cabrera. The Sahel engulfed by violence, climate change, food insecurity and extremists are largely to blame. in World Economic Forum. 2019.
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Overpopulation: Cause and Effect

Conversations about overpopulation can quickly become controversial because they beg the question: Who exactly is the cause of the problem and what, if anything, should be done about it? Many population experts worry discussions around overpopulation will be abused by small-minded people to suggest some are the “right people” to be on the planet (like themselves), and some people are “the wrong people” (usually people in poverty, people of color, foreigners, and so on—you get the drift). But there are no “right” or “wrong” people on the planet, and discussing the problems of global overpopulation can never be an excuse, or in any way provide a platform, for having that type of conversation.

Each human being has a legitimate claim on a sufficient and fair amount of Earth’s resources. But with a population approaching 8 billion, even if everyone adopted a relatively low material standard of living like the one currently found in Papua New Guinea , it would still push Earth to its ecological breaking point. Unfortunately, the “average person” on Earth consumes at a rate over 50% above a sustainable level. Incredibly, the average person in the United States uses almost five times more than the sustainable yield of the planet.

When we use the term “overpopulation,” we specifically mean a situation in which the Earth cannot regenerate the resources used by the world’s population each year. Experts say this has been the case every year since 1970, with each successive year becoming more and more damaging. To help temper this wildly unsustainable situation, we need to understand what’s contributing to overpopulation and overconsumption and how these trends are affecting everything from climate change to sociopolitical unrest.

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The causes of overpopulation.

Today the Earth is home to over 8 billion people. By 2100 the population is on track to hit 10.8 billion , according to the United Nations — and that’s assuming steady fertility declines in many countries. Interestingly, if extra progress is made in women’s reproductive self-determination, and fertility falls more than the United Nations assumes is likely, the population in 2100 might be a relatively smaller 7.3 billion.

For now, the world’s population is still increasing in huge annual increments (about 80 million per year), and our supply of vital non-renewable resources are being exhausted. Many factors contribute to these unsustainable trends , including falling mortality rates, underutilized contraception, and a lack of education for girls.

Falling Mortality Rate

The primary (and perhaps most obvious) cause of population growth is an imbalance between births and deaths. The infant mortality rate has decreased globally, with 4.1 million infant deaths in 2017 compared to 8.8 million in 1990, according to the World Health Organization (WHO). This is welcome public health news, of course.

At the same time, lifespans are increasing around the world. Those of us who are alive today will likely live much longer than most of our ancestors. Global average life expectancy has more than doubled since 1900 , thanks to advancements in medicine, technology, and general hygiene. Falling mortality rates are certainly nothing to complain about either, but widespread longevity does contribute to the mathematics of increasing population numbers.

Underutilized Contraception 

The global fertility rate has fallen steadily over the years, down from an average of 5 children per woman in 1950 to 2.4 children per woman today, according to the UN Population Division . Along with that promising trend, contraceptive use has slowly but steadily increased globally, rising from 54% in 1990 to 57.4% in 2015. Yet, on the whole, contraceptive use is still underutilized. For example, according to the WHO, an estimated 214 million women in developing countries who want to avoid pregnancy are not using modern contraceptives.

These women aren’t using contraceptives for a variety of reasons, including social norms or religious beliefs that discourage birth control, misconceptions about adverse side effects, and a lack of agency for women to make decisions around sex and family planning. An estimated 44% of pregnancies were unintended worldwide between 2010-2014. Getting more women the access and agency to utilize family planning methods could go a long way in flattening the population curve.

Lack of Female Education    

Although female access to education has increased over the years, the gender gap remains. Roughly 130 million girls worldwide are out of school currently, and an estimated 15 million girls of primary school age will never   learn to read and write, compared with 10 million boys.

Increasing and encouraging education among women and girls can have a number of positive ripple effects, including delayed childbearing , healthier children, and an increase in workforce participation. Plenty of evidence suggests a negative correlation between female education and fertility rates.

If increased female education can delay or decrease fertility and provide girls with opportunities beyond an early marriage, it could also help to mitigate current population trends. 

The Effects of Overpopulation

It is only logical that an increase in the world’s population will cause additional strains on resources. More people means an increased demand for food, water, housing, energy, healthcare, transportation, and more. And all that consumption contributes to ecological degradation, increased conflicts, and a higher risk of large-scale disasters like pandemics.  

Ecological Degradation 

An increase in population will inevitably create pressures leading to more deforestation, decreased biodiversity, and spikes in pollution and emissions, which will exacerbate climate change . Ultimately, unless we take action to help minimize further population growth heading into the remainder of this century, many scientists believe the additional stress on the planet will lead to ecological disruption and collapse so severe it threatens the viability of life on Earth as we know it. 

Each spike in the global population has a measurable impact on the planet’s health. According to estimates in a study by Wynes and Nicholas (2017) , a family having one fewer child could reduce emissions by 58.6 tonnes CO2-equivalent per year in developed countries.

Increased Conflicts 

The scarcity brought about by environmental disruption and overpopulation has the potential to trigger an increase in violence and political unrest. We’re already seeing wars fought over water, land, and energy resources in the Middle East and other regions, and the turmoil is likely to increase as the global population grows even larger.

Higher Risk of Disasters and Pandemics 

Many of the recent novel pathogens that have devastated humans around the world, including COVID-19, Zika virus, Ebola, and West Nile virus, originated in animals or insects before passing to humans. Part of the reason the world is entering “ a period of increased outbreak activity ” is because humans are destroying wildlife habitats and coming into contact with wild animals on a more regular basis. Now that we’re in the midst of a pandemic, it has become clear how difficult it is to social distance in a world occupied by nearly 8 billion people.   

Discover the real causes and effects of overpopulation

What can be done about overpopulation.

When addressing overpopulation, it’s crucial to take an approach of providing empowerment while mobilizing against anybody advocating for the use of coercion or violence to solve our problems. The combined efforts of spreading knowledge about family planning, increasing agency among women , and debunking widely held myths about contraception will measurably change the trajectory of the world’s population.

As we carry out our work at Population Media Center (PMC), we see first-hand that spreading awareness about family planning methods and the ecological and economic benefits of having smaller families can change reproductive behavior. For example, listeners of our Burundian radio show Agashi (“Hey! Look Again!”) were 1.7 times more likely than non-listeners to confirm that they were willing to negotiate condom use with a sexual partner and 1.8 times more likely than non-listeners to say that they generally approve of family planning for limiting the number of children.

CELEBRATING EARTH DAY WITH CONVERSATIONS ON OVERPOPULATION

In the spirit of Earth Day, it’s crucial to approach discussions about overpopulation with sensitivity and inclusivity. Overpopulation conversations should focus on the collective responsibility to steward Earth’s resources sustainably, rather than assigning blame or dividing communities. By fostering understanding and promoting access to education and reproductive health services, we can work towards a more equitable and sustainable future for all.

At PMC we harness the power of storytelling to empower listeners to live healthier and more prosperous lives, which in turn contributes to stabilizing the global population so that people can live sustainably with the world’s renewable resources. Discover how PMC is taking action against overpopulation today!

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Impact of Population Growth

John P. Holdren , Paul R. Ehrlich | October 22, 2019 | Leave a Comment Download as PDF

It is more important now than ever to talk about population. What will we do if we continue to grow at exponential rates? What are ethical, viable strategies to decrease population?

This is a blog in the  MAHB Let’s Talk About Population Blog Series.

Complacency concerning this component of man’s predicament is unjustified and counterproductive.

The interlocking crises in population, resources, and environment have been the focus of countless papers, dozens of prestigious symposia, and a growing avalanche of books. In this wealth of material, several questionable assertions have been appearing with increasing frequency. Perhaps the most serious of these is the notion that the size and growth rate of the U.S. population are only minor contributors to this country’s adverse impact on local and global environments (1, 2). We propose to deal with this and several related misconceptions here, before persistent and unrebutted repetition entrenches them in the public mind—if not the scientific literature. Our discussion centers around five theorems which we believe are demonstrably true and which provide a framework for realistic analysis:

• Population growth causes a disproportionate negative impact on the environment.
• Problems of population size and growth, resource utilization and depletion, and environmental deterioration must be considered jointly and on a global basis. In this context, population control is obviously not a panacea—it is necessary but not alone sufficient to see us through the crisis.
• Population density is a poor measure of population pressure, and redistributing population would be a dangerous pseudosolution to the population problem.
• “Environment” must be broadly construed to include such things as the physical environment of urban ghettos, the human behavioral environment, and the epidemiological environment.
• Theoretical solutions to our problems are often not operational and sometimes are not solutions.

We now examine these theorems in some detail.

Population Size and Per Capita Impact

In an agricultural or technological society, each human individual has a negative impact on his environment. He is responsible for some of the simplification (and resulting destabilization) of ecological systems which results from the practice of agriculture (3). He also participates in the utilization of renewable and nonrenewable resources. The total negative impact of such a society on the environment can be expressed, in the simplest terms, by the relation

where P is the population, and F is a function which measures the per capita impact. A great deal of complexity is subsumed in this simple relation, however. For example, F increases with per capita consumption if technology is held constant, but may decrease in some cases if more benign technologies are introduced in the provision of a constant level of consumption. (We shall see in connection with theorem 5 that there are limits to the improvements one should anticipate from such “technological fixes.’’)

Pitfalls abound in the interpretation of manifest increases in the total impact I . For instance, it is easy to mistake changes in the composition of resource demand or environmental impact for absolute per capita increases, and thus to underestimate the role of the population multiplier. Moreover, it is often assumed that population size and per capita impact are independent variables, when in fact they are not. Consider, for example, the recent article by Coale (1), in which he disparages the role of U.S. population growth in environmental problems by noting that since 1940 “population has increased by 50 percent, but per capita use of electricity has been multiplied several times.” This argument contains both the fallacies to which we have just referred.

First, a closer examination of very rapid increases in many kinds of consumption shows that these changes reflect a shift among alternatives within a larger (and much more slowly growing) category. Thus the 760 percent increase in electricity consumption from 1940 to 1969 (4) occurred in large part because the electrical component of the energy budget was (and is) increasing much faster than the budget itself. (Electricity comprised 12 percent of the U.S. energy consumption in 1940 versus 22 percent today.) The total energy use, a more important figure than its electrical component in terms of resources and the environment, increased much less dramatically—140 percent from 1940 to 1969. Under the simplest assumption (that is, that a given increase in population size accounts for an exactly proportional increase in consumption), this would mean that 38 percent of the increase in energy use during this period is explained by population growth (the actual population increase from 1940 to 1969 was 53 percent). Similar considerations reveal the imprudence of citing, say, aluminum consumption to show that population growth is an “unimportant” factor in resource use. Certainly, aluminum consumption has swelled by over 1400 percent since 1940, but much of the increase has been due to the substitution of aluminum for steel in many applications. Thus a fairer measure is combined consumption of aluminum and steel, which has risen only 117 percent since 1940. Again, under the simplest assumption, population growth accounts for 45 percent of the increase.

The “simplest assumption” is not valid, however, and this is the second flaw in Coale’s example (and in his thesis). In short, he has failed to recognize that per capita consumption of energy and resources, and the associated per capita impact on the environment, are themselves functions of the population size. Our previous equation is more accurately written

I = P • F (P)

displaying the fact that impact can increase faster than linearly with population. Of course, whether F (P) is an increasing or decreasing function of P depends in part on whether diminishing returns or economies of scale are dominant in the activities of importance. In populous, industrial nations such as the United States, most economies of scale are already being exploited; we are on the diminishing returns part of most of the important curves,

As one example of diminishing returns, consider the problem of providing nonrenewable resources such as minerals and fossil fuels to a growing population, even at fixed levels of per capita consumption, As the richest supplies of these resources and those nearest to centers of use are consumed, we are obliged to use lower-grade ores, drill deeper, and extend our supply networks. All these activities increase our per capita use of energy and our per capita impact on the environment. In the case of partly renewable resources such as water (which is effectively nonrenewable when groundwater supplies are mined at rates far exceeding natural recharge), per capita costs and environmental impact escalate dramatically when the human population demands more than is locally available. Here the loss of free-flowing rivers and other economic, esthetic, and ecological costs of massive water-movement projects represent increased per capita diseconomies directly stimulated by population growth.

Diminishing returns are also operative in increasing food production to meet the needs of growing populations. Typically, attempts are made both to overproduce on land already farmed and to extend agriculture to marginal land. The former requires disproportionate energy use in obtaining and distributing water, fertilizer, and pesticides. The latter also increases per capita energy use, since the amount of energy invested per unit yield increases as less desirable land is cultivated. Similarly, as the richest fisheries stocks are depleted, the yield per unit effort drops, and more and more energy per capita is required to maintain the supply (5). Once a stock is depleted it may not recover—it may be nonrenewable.

Population size influences per capita impact in ways other than diminishing returns. As one example, consider the oversimplified but instructive situation in which each person in the population has links with every other person—roads, telephone lines, and so forth. These links involve energy and materials in their construction and use. Since the number of links increases much more rapidly than the number of people (6), so does the per capita consumption associated with the links.

Other factors may cause much steeper positive slopes in the per capita impact function, F(P) . One phenomenon is the threshold effect . Below a certain level of pollution trees will survive in smog. But, at some point, when a small increment in population produces a small increment in smog, living trees become dead trees. Five hundred people may be able to live around a lake and dump their raw sewage into the lake, and the natural systems of the lake will be able to break down the sewage and keep the lake from undergoing rapid ecological change. Five hundred and five people may overload the system and result in a “polluted” or eutrophic lake. Another phenomenon capable of causing near-discontinuities is the synergism . For instance, as cities push out into farmland, air pollution increasingly becomes a mixture of agricultural chemicals with power plant and automobile effluents. Sulfur dioxide from the city paralyzes the cleaning mechanisms of the lungs, thus increasing the residence time of potential carcinogens in the agricultural chemicals. The joint effect may be much more than the sum of the individual effects. Investigation of synergistic effects is one of the most neglected areas of environmental evaluation.

Not only is there a connection between population size and per capita damage to the environment, but the cost of maintaining environmental quality at a given level escalates disproportionately as population size increases. This effect occurs in part because costs increase very rapidly as one tries to reduce contaminants per unit volume of effluent to lower and lower levels (diminishing returns again!). Consider municipal sewage, for example. The cost of removing 80 to 90 percent of the biochemical and chemical oxygen demand, 90 percent of the suspended solids, and 60 percent of the resistant organic material by means of secondary treatment is about 8 cents per 1000 gallons (3785 liters) in a large plant (7). But if the volume of sewage is such that its nutrient content creates a serious eutrophication problem (as is the case in the United States today), or if supply considerations dictate the reuse of sewage water for industry, agriculture, or groundwater recharge, advanced treatment is necessary. The cost ranges from two to four times as much as for secondary treatment (17 cents per 1000 gallons for carbon absorption; 34 cents per 1000 gallons for disinfection to yield a potable supply). This dramatic example of diminishing returns in pollution control could be repeated for stack gases, automobile exhausts, and so forth.

Now consider a situation in which the limited capacity of the environment to absorb abuse requires that we hold man’s impact in some sector constant as population doubles. This means per capita effectiveness of pollution control in this sector must double (that is, effluent per person must be halved). In a typical situation, this would yield doubled per capita costs, or quadrupled total costs (and probably energy consumption) in this sector for a doubling of population. Of course, diminishing returns and threshold effects may be still more serious: we may easily have an eightfold increase in control costs for a doubling of population. Such arguments leave little ground for the assumption, popularized by Barry Commoner (2, 8) and others, that a 1 percent rate of population growth spawns only 1 percent effects.

It is to be emphasized that the possible existence of “economies of scale” does not invalidate these arguments. Such savings, if available at all, would apply in the case of our sewage example to a change in the amount of effluent to be handled at an installation of a given type. For most technologies, the United States is already more than populous enough to achieve such economies and is doing so. They are accounted for in our example by citing figures for the largest treatment plants of each type. Population growth, on the other hand, forces us into quantitative and qualitative changes in how we handle each unit volume of effluent—what fraction and what kinds of material we remove. Here economies of scale do not apply at all, and diminishing returns are the rule.

Global Context

We will not deal in detail with the best example of the global nature and interconnections of population resource and environmental problems—namely, the problems involved in feeding a world in which 10 to 20 million people starve to death annually (9), and in which the population is growing by some 70 million people per year. The ecological problems created by high-yield agriculture are awesome (3, 10) and are bound to have a negative feedback on food production. Indeed, the Food and Agriculture Organization of the United Nations has reported that in 1969 the world suffered its first absolute decline in fisheries yield since 1950. It seems likely that part of this decline is attributable to pollution originating in terrestrial agriculture.

A second source of the fisheries decline is, of course, overexploitation of fisheries by the developed countries. This problem, in turn, is illustrative of the situation in regard to many other resources, where similarly rapacious and shortsighted behavior by the developed nations is compromising the aspirations of the bulk of humanity to a decent existence. It is now becoming more widely comprehended that the United States alone accounts for perhaps 30 percent of the nonrenewable resources consumed in the world each year (for example, 37 percent of the energy, 25 percent of the steel, 28 percent of the tin, and 33 percent of the synthetic rubber) (11). This behavior is in large part inconsistent with American rhetoric about “developing” the countries of the Third World. We may be able to afford the technology to mine lower grade deposits when we have squandered the world’s rich ores, but the underdeveloped countries, as their needs grow and their means remain meager, will not be able to do so. Some observers argue that the poor countries are today economically dependent on our use of their resources, and indeed that economists in these countries complain that world demand for their raw materials is too low (1). This proves only that their economists are as shortsighted as ours.

It is abundantly clear that the entire context in which we view the world resource pool and the relationships between developed and underdeveloped countries must be changed, if we are to have any hope of achieving a stable and prosperous existence for all human beings. It cannot be stated too forcefully that the developed countries (or, more accurately, the overdeveloped countries) are the principal culprits in the consumption and dispersion of the world’s nonrenewable resources (12) as well as in appropriating much more than their share of the world’s protein. Because of this consumption, and because of the enormous negative impact on the global environment accompanying it, the population growth in these countries must be regarded as the most serious in the world today.

In relation to theorem 2 we must emphasize that, even if population growth were halted, the present population of the world could easily destroy civilization as we know it. There is a wide choice of weapons—from unstable plant monocultures and agricultural hazes to DDT, mercury, and thermonuclear bombs. If population size were reduced and per capita consumption remained the same (or increased), we would still quickly run out of vital, high-grade resources or generate conflicts over diminishing supplies. Racism, economic exploitation, and war will not be eliminated by population control (of course, they are unlikely to be eliminated without it).

Population Density and Distribution

Theorem 3 deals with a problem related to the inequitable utilization of world resources. One of the commonest errors made by the uninitiated is to assume that population density (people per square mile) is the critical measure of overpopulation or underpopulation. For instance, Wattenberg states that the United States is not very crowded by “international standards” because Holland has 18 times the population density (13). We call this notion “the Netherlands fallacy.” The Netherlands actually requires large chunks of the earth’s resources and vast areas of land not within its borders to maintain itself. For example, it is the second largest per capita importer of protein in the world, and it imports 63 percent of its cereals, including 100 percent of its corn and rice. It also imports all of its cotton, 77 percent of its wool, and all of its iron ore, antimony, bauxite, chromium, copper, gold, lead, magnesite, manganese, mercury, molybdenum, nickel, silver, tin, tungsten, vanadium, zinc, phosphate rock (fertilizer), potash (fertilizer), asbestos, and diamonds. It produces energy equivalent to some 20 million metric tons of coal and consumes the equivalent of over 47 million metric tons (14).

A certain preoccupation with density as a useful measure of overpopulation is apparent in the article by Coale (1). He points to the existence of urban problems such as smog in Sydney, Australia, “even though the total population of Australia is about 12 million in an area 80 percent as big as the United States,” as evidence that environmental problems are unrelated to population size. His argument would be more persuasive if problems of population distribution were the only ones with environmental consequences, and if population distribution were unrelated to resource distribution and population size. Actually, since the carrying capacity of the Australian continent is far below that of the United States, one would expect distribution problems—of which Sydney’s smog is one symptom—to be encountered at a much lower total population there. Resources, such as water, are in very short supply, and people cluster where resources are available. (Evidently, it cannot be emphasized enough that carrying capacity includes the availability of a wide variety of resources in addition to space itself, and that population pressure is measured relative to the carrying capacity. One would expect water, soils, or the ability of the environment to absorb wastes to be the limiting resource in far more instances than land area.)

In addition, of course, many of the most serious environmental problems are essentially independent of the way in which population is distributed. These include the global problems of weather modification by carbon dioxide and particulate pollution, and the threats to the biosphere posed by man’s massive inputs of pesticides, heavy metals, and oil (15). Similarly, the problems of resource depletion and ecosystem simplification by agriculture depend on how many people there are and their patterns of consumption, but not in any major way on how they are distributed.

Naturally, we do not dispute that smog and most other familiar urban ills are serious problems, or that they are related to population distribution. Like many of the difficulties we face, these problems will not be cured simply by stopping population growth; direct and well-conceived assaults on the problems themselves will also be required. Such measures may occasionally include the redistribution of population, but the considerable difficulties and costs of this approach should not be underestimated. People live where they do not because of a perverse intention to add to the problems of their society but for reasons of economic necessity, convenience, and desire for agreeable surroundings. Areas that are uninhabited or sparsely populated today are presumably that way because they are deficient in some of the requisite factors. In many cases, the remedy for such deficiencies—for example, the provision of water and power to the wastelands of central Nevada—would be extraordinarily expensive in dollars, energy, and resources and would probably create environmental havoc. (Will we justify the rape of Canada’s rivers to “colonize” more of our western deserts?)

Moving people to more “habitable” areas, such as the central valley of California or, indeed, most suburbs, exacerbates another serious problem— the paving-over of prime farmland. This is already so serious in California that, if current trends continue, about 50 percent of the best acreage in the nation’s leading agricultural state will be destroyed by the year 2020 (16). Encouraging that trend hardly seems wise.

Whatever attempts may be made to solve distribution-related problems, they will be undermined if population growth continues, for two reasons. First, population growth and the aggravation of distribution problems are correlated—part of the increase will surely be absorbed in urban areas that can least afford the growth. Indeed, barring the unlikely prompt reversal of present trends, most of it will be absorbed there. Second, population growth puts a disproportionate drain on the very financial resources needed to ’combat its symptoms. Economist Joseph Spengler has estimated that 4 percent of national income goes to support our 1 percent per year rate of population growth in the United States (17). The 4 percent figure now amounts to about $30 billion per year. It seems safe to conclude that the faster we grow the less likely it is that we will find the funds either to alter population distribution patterns or to deal more comprehensively and realistically with our problems.

Meaning of Environment

Theorem 4 emphasizes the comprehensiveness of the environment crisis. All too many people think in terms of national parks and trout streams when they say “environment.” For this reason many of the suppressed people of our nation consider ecology to be just one more “racist shuck” (18). They are apathetic or even hostile toward efforts to avert further environmental and sociological deterioration, because they have no reason. to believe they will share the fruits of success (19). Slums, cockroaches, and rats are ecological problems, too. The correction of ghetto conditions in Detroit is neither more nor less important than saving the Great Lakes—both are imperative.

We must pay careful attention to sources of conflict both within the United States and between nations. Conflict within the United States blocks progress toward solving our problems; conflict among nations can easily “solve” them once and for all. Recent laboratory studies on human beings support the anecdotal evidence that crowding may increase aggressiveness in human males (20). These results underscore long-standing suspicions that population growth, translated through the inevitable uneven distribution into physical crowding, will tend to make the solution of all of our problems more difficult.

As a final example of the need to view “environment” broadly, note that human beings live in an epidemiological environment which deteriorates with crowding and malnutrition—both of which increase with population growth. The hazard posed by the prevalence of these conditions in the world today is compounded by man’s unprecedented mobility: potential carriers of diseases of every description move routinely and in substantial numbers from continent to continent in a matter of hours. Nor is there any reason to believe that modern medicine has made widespread plague impossible (21). The Asian influenza epidemic of 1968 killed relatively few people only because the virus happened to be nonfatal to people in otherwise good health, not because of public health measures. Far deadlier viruses, which easily could be scourges without precedent in the population at large, have on more than one occasion been confined to research workers largely by good luck [for example, the Marburg virus incident of 1967 (22) and the Lassa fever incident of 1970 (21, 23)].

Solutions: Theoretical and Practical

Theorem 5 states that theoretical solutions to our problems are often not operational, and sometimes are not solutions. In terms of the problem of feeding the world, for example, technological fixes suffer from limitations in scale, lead time, and cost (24). Thus potentially attractive theoretical approaches—such as desalting seawater for agriculture, new irrigation systems, high-protein diet supplements—prove inadequate in practice. They are too little, too late, and too expensive, or they have sociological costs which hobble their effectiveness (25). Moreover, many aspects of our technological fixes, such as synthetic organic pesticides and inorganic nitrogen fertilizers, have created vast environmental problems which seem certain to erode global productivity and ecosystem stability (26). This is not to say that important gains have not been made through the application of technology to agriculture in the poor countries, or that further technological advances are not worth seeking. But it must be stressed that even the most enlightened technology cannot relieve the necessity of grappling forthrightly and promptly with population growth [as Norman Borlaug aptly observed on being notified of his Nobel Prize for development of the new wheats (27)].

Technological attempts to ameliorate the environmental impact of population growth and rising per capita affluence in the developed countries suffer from practical limitations similar to those just mentioned. Not only do such measures tend to be slow, costly, and insufficient in scale, but in addition they most often shift our impact rather than remove it. For example, our first generation of smog-control devices increased emissions of oxides of nitrogen while reducing those of hydrocarbons and carbon monoxide. Our unhappiness about eutrophication has led to the replacement of phosphates in detergents with compounds like NTA—nitrilotriacetic acid—which has carcinogenic breakdown products and apparently enhances teratogenic effects of heavy metals (28). And our distaste for lung diseases apparently induced by sulfur dioxide inclines us to accept the hazards of radioactive waste disposal, fuel reprocessing, routine low-level emissions of radiation, and an apparently small but finite risk of catastrophic accidents associated with nuclear fission power plants. Similarly, electric automobiles would simply shift part of the environmental burden of personal transportation from the vicinity of highways to the vicinity of power plants.

We are not suggesting here that electric cars, or nuclear power plants, or substitutes for phosphates are inherently bad. We argue rather that they, too, pose environmental costs which must be weighed against those they eliminate. In many cases the choice is not obvious, and in all cases there will be some environmental impact. The residual per capita impact, after all the best choices have been made, must then be multiplied by the population engaging in the activity. If there are too many people, even the most wisely managed technology will not keep the environment from being overstressed.

In contending that a change in the way we use technology will invalidate these arguments, Commoner (2, 8) claims that our important environmental problems began in the 1940’s with the introduction and rapid spread of certain “synthetic” technologies: pesticides and herbicides, inorganic fertilizers, plastics, nuclear energy, and high-compression gasoline engines. In so arguing, he appears to make two unfounded assumptions. The first is that man’s pre-1940 environmental impact was innocuous and, without changes for the worse in technology, would have remained innocuous even at a much larger population size. The second assumption is that the advent of the new technologies was independent of the attempt to meet human needs and desires in a growing population. Actually, man’s record as a simplifier of ecosystems and plunderer of resources can be traced from his probable role in the extinction of many Pleistocene mammals (29), through the destruction of the soils of Mesopotamia by salination and erosion, to the deforestation of Europe in the Middle Ages and the American dustbowls of the 1930’s, to cite only some highlights. Man’s contemporary arsenal of synthetic technological bludgeons indisputably magnifies the potential for disaster, but these were evolved in some measure to cope with population pressures, not independently of them. Moreover, it is worth noting that, of the four environmental threats viewed by the prestigious Williamstown study (15) as globally significant, three are associated with pre-1940 technologies which have simply increased in scale [heavy metals, oil in the seas, and carbon dioxide and particulates in the atmosphere, the latter probably due in considerable part to agriculture (30)]. Surely, then, we can anticipate that supplying food, fiber, and metals for a population even larger than today’s will have a profound (and destabilizing) effect on the global ecosystem under any set of technological assumptions.

John Platt has aptly described man’s present predicament as “a storm of crisis problems” (31). Complacency concerning any component of these problems—sociological, technological, economic, ecological—is unjustified and counterproductive. It is time to admit that there are no monolithic solutions to the problems we face. Indeed, population control, the redirection of technology, the transition from open to closed resource cycles, the equitable distribution of opportunity and the ingredients of prosperity must all be accomplished if there is to be a future worth having. Failure in any of these areas will surely sabotage the entire enterprise.

In connection with the five theorems elaborated here, we have dealt at length with the notion that population growth in industrial nations such as the United States is a minor factor, safely ignored. Those who so argue often add that, anyway, population control would be the slowest to take effect of all possible attacks on our various problems, since the inertia in attitudes and in the age structure of the population is so considerable. To conclude that this means population control should be assigned low priority strikes us as curious logic. Precisely because population is the most difficult and slowest to yield among the components of environmental deterioration, we must start on it at once. To ignore population today because the problem is a tough one is to commit ourselves to even gloomier prospects 20 years hence, when most of the “easy” means to reduce per capita impact on the environment will have been exhausted. The desperate and repressive measures for population control which might be contemplated then are reason in themselves to proceed with foresight, alacrity, and compassion today.

This article was originally published in Science on March 26, 1971. To review the sources, please download the article here .

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Population Growth and Economic Development: Policy Questions (1986)

Chapter: conclusion.

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Conclusion We have examined a diverse set of mechanisms through which population growth affects economic development. This chapter opens with a review and synthesis of our conclusions on the expected effects of a decline in the population grown rate that works through these mechanisms. It then proceeds to a discussion of how environmental and institutional contexts mediate the actions of these mechanisms a major theme of this report. The final section discusses policy implications. EFFECTS OF SLOWER POPULATION GROWTH ON ECONOMIC DEVELOPMENT Following the framework set up in the Introduction, we consider how conditions are likely to differ if a country, through a government program, were to achieve and maintain lower fertilibr than it would otherwise have experienced (with constant mortality). As noted above, such a decline would produce at every subsequent point slower population growth, smaller population size, lower population density, and an older age structure. Working through these direct demographic effects, a reduced level of fertility is also likely to produce several other changes. Slower Population Growth and Exhaustible Resources Globally slower population growth may delay the time at which a particular stage of depletion of an exhaustible resource is reached. This effect does not necessarily increase the number of people who will have access to 85

86 POPUW7ON GROWTH AND ECONOMIC DEVELOPMENT that resource; rather, it moves the consumption stream further from the present. But it is important to recognize that no single exhaustible resource is essential or irreplaceable; it is valued for its economic contribution, not for its own sake. As easily accessible reserves of natural resources are exhausted, the real cost of extraction, and hence the resource pace, rises. This price rise should stimulate the search for alternative materials. Historically, these adaptive strategies have been extremely successful. To the extent that slower population growth results in a slower rate of resource depletion, these adaptive strategies will also occur more slowly. Hence, it seems unlikely that slower population growth will allow a larger number of people, over future generations, to enjoy a given standard of living thanks to lower natural resource prices. Slower Population Growth and Renewable Resources Slower population growth, in some cases nationally and in others globally, is likely to lead to a reduced rate of degradation of renewable common- property resources such as air, water, and species of plants and animals. If significant amounts of land and forest resources are held in common in a country, they will also tend to be degraded less rapidly. These effects are likely to be more evident in the short run-in say, a decade or two. In the long run, population growth itself might create greater incentives to develop the social and political institutions necessary for conservation. Such incentives are irrelevant, of course, if the resource has become depleted beyond the point of restoration. Moreover, changes are costly and the need to bear such costs is itself a consequence of population growth. Slower Population Growth, Health, and Education Lower fertility is likely to raise average per child levels of household expenditure on health and education and thereby improve levels of child health and education. By themselves, such changes should result in a more productive labor force. Superimposed on these within-family effects is the possibility that lower fertility will alter the distribution of children among families by income class. If fertility declines are largest among high- income families, average levels of schooling and health among children could actually decrease despite an absolute improvement in measures of well-being among poor families. But if family planning programs result in larger fertilibr reductions among poorer families, the within-family gains will be accentuated at the societal level. Slower population growth is likely to raise public expenditures on schooling per school-aged child. Evidence from the educational literature suggests that

CONCLUSION 87 such a result may lead to some improvement in educational quality as measured, for example, by test scores. We do not find convincing evidence that lower fertility will result in faster growth in enrollment ratios (apart from within-family effects). Slower Population Growth and Income Unless a fertility decline is concentrated among high-income families, it is likely to lead to a reduction in income disparities among social classes. This is primarily a long-term effect (although a variety of short-tenn effects are also possible) and wows primarily by raising payments to labor relative to payments to capital and raising payments to unskilled labor relative to skilled labor. We have found little evidence that the aggregate savings rate depends on growth rates or the age structure of a population. Assuming that the savings rate remains unchanged, a fertility decline will lead to an increase in the ratio of capital to labor and, along with it, labor productivity, wages, and per capita income. The increase in the capitalllabor ratio will reduce rates of ran to capital and reduce payments to owners of capital. In the short run, more land per agricultural worker is likely to raise labor productivity in agriculture. Long-term effects may differ because of changes in the organization and techniques of production that are induced by the relative change in factor availability. These effects may reduce the short- term gains of slower growth. Slower Population Growth and Cities Win slower population growth, cities grow more slowly, both in the short and long run. Natural increase (~e excess of birds over deaths) accounts for about 60 percent of city growth today in developing countnes, and it is reasonable to expect that a decline in fertilizer levels will entail a decline in rates of natural increase in cities. Such changes reduce the demand for urban infras~uctural investments while eventually reducing the revenue base that supports such investments. The evidence on Chewer reduced national fertility levels reduce the rate of rural-url~an migration, and hence reduce He rate of grown of He proportion of He population that is urban, is unclear. A reduced rate of urban labor force grown in developing countries (most of which is a product of natural increase among the urban population) is not likely to be systematically accompanied by corresponding reductions in joblessness. However, it may increase He proportion of He urban labor force working in high-wage jobs in the modern sector of the economy and reduce He proportion working in the low-wage, infonnal sector.

88 POP CLARION GROWN AND ECONOMIC DEVEL()PMENT ENVIRONMENTAL AND INSTITUTIONAL CONTEXTS It is clear that the economic advantages of fertility reduction will vary from place to place. Environmental and climatic conditions clearly shape the local impact of population growth. In countries such as Bangladesh, where ratios of agricultural labor to arable land are already very high, there is a presumptive case that labor productivity in agriculture will decline more rapidly with added labor than if ratios were low. Nonagricultural production possibilities, and the opportunities for trade, also affect the importance of these natural features. Important as these natural features may be in conditioning the economic response to population growth, Hey appear to be far less important than conditions created by people. Many of the initial effects of population growth are negative, but they can be ameliorated or even reversed in the long run if institutional adjustment mechanisms are in place. Among the most important of such mechanisms are property rights in land and properly functioning markets for labor, capital, and goods. Such markets permit the initial effects of population growth to be registered in the fonn of price changes, which can trigger a variety of adjustments, including the introduction of other factors of production that have become more valuable as a result of the increase in population; a search for substitutes for increasingly scarce factors of production; intensified research to find production processes better suited to the new conditions; reallocation of resources toward sectors (e.g., food production) in which demand may be most responsive to population change; and so on. Of course, these adjustments may entail real costs, even when these are minimized by efficient institutions. When markets function very poorly, or do not exist, adjustments to population change are likely to be slower or to not occur at all. These are not merely theoretical notions. Some part of the current distress in Ethiopia, of the loss of 30 million lives during China's '~great leap forward" (Ashton et al., 1984), and of the problems of food production in tropical Africa during the 1970s was due to very badly functioning markets combined with rapid population grown. Even efficient markets do not guarantee desirable outcomes. The famines of 1942-1943 in Bengal and of 1973-1974 in Bangladesh seem to have been principally a result of deterioration in the income distribution-in particular, the loss of purchasing power by unskilled wage laborers-combined with speculative hoarding in food markets (See, 1981~. This kind of outcome underscores the role of the distribution of wealth and of human capital as a fundamental determinant of poverty. The potential value of government intervention for market regulation and for purposes of income distribution is widely acknowledged. Govemment policies in a variety of arenas clearly play important roles in mediating Me

CONCLUSION 89 impact of population growth. Effects of population growth on educational enrollment and quality, on rates of exploitation of common property resources, on the development of social and economic infrastructure, on urbanization, and on research activities are all heavily dependent on existing government policies and their adaptiveness to changed conditions. In short, the effects of rapid population growth are likely to be conditioned by the quality of markets, the nature of government policies, and features of the natural environment. Since the effects are so dependent on these conditions, a reliable assessment of many of the net effects of population growth can best be carried out at the national level, although some issues concerning the environment and resources can only be analyzed globally. It is of interest to briefly examine and contrast Me interplay between population grown and institutions in two important areas, China and tropical Africa. China, with its extremely low arable landlpopulation ratio, is often seen as greatly in need of population control policies in order to boost per capita agricultural income; this view is reflected in the government's severe disincentives for large families. Although it is possible Mat the resultant decline in the population growth rate has somewhat increased per capita agricultural income, these gains are probably small compared with those from agricultural reforms instituted in 1979. Over the period 1979-1984, the real per capita income of Me rural population increased 15 percent annually, and total agricultural output increased 51 percent (U.S. Department of Agriculture, 1985; Li, 1985~. In contrast, tropical Africa has a comparatively high land/population ratio, but appears to be particularly vulnerable to problems induced by population grown. Political independence and He forces of modernization came to tropical Africa later than to other areas. Although some countries in other regions also share these traits, markets are generally least well developed in tropical Africa, political factionalism is greatest, and human resource potential is least developed. In parts of Africa, sparseness of population itself may be responsible for some of these difficulties, but this explanation is implausible for such countries as Ethiopia or Kenya Obviously, slowing population growth is not a substitute for solving other problems, but it can reduce some of the more extreme manifestations of these problems while they are being solved. SUMMARY Population growth can, and often does, trigger market reactions. Many of these reactions move a country in a '`modem" direction, that is, toward better~efined properq rights, larger integrated marked, more agocultum1 research, and so on. However, He market-induced adjustments to higher

go POP ULA77ON GROWTH AND ECONOMIC DEVELOPMENT growth do not appear to be large enough to offset the negative effects on per capita income of higher ratios of labor to other factors of production. Nor is population growth necessary to achieve these forms of modernization: the fact that rates of return to agricultural research are already extremely high-in bow developing and developed countnes-implies Mat Here is little need for additional stimulus from population growth; the evolution of property rights is stimulated by many factors~population grown being only one among Rem (Binswanger and Pingali, 1984~; and the scope of many markets can be enlarged by removing made barriers. That these over devices exist does not imply a minimal role for population grown, but it does caution against advocacy of growth as the only way to achieve them. On balance, we reach the qualitative conclusion Cat slower population growth would be beneficial to economic development for most developing counties. A rigorous quantitative assessment of these benefits is difficult and context dependent. Since we have stressed the role of slower population growth in raising per capita human and physical capital, it is instructive to use as a benchmark the effects of changes in the ratio of physical capital per person. A simple mode} suggests that the effect is comparatively modest. Using a typical labor coefficient of 0.5 in estimated production functions, a 1 percent reduction in the me of labor force growth would boost the grown of per capita income by 0.5 percent per year. ~us, after 30 years, a 1 percent reduction in the annual rate of population grown (produced, say, by a decline in Be crude bird rate from 37 to 27 per 1,0003 will have raised production and income per capita to a level 16 percent above what it would otherwise have been. This would be a substantial gain, but by no means enough to vault a typical developing country into Be ranks of the developed. This simple calculation, however, does not fully reflect the complexity of Be linkages between population growth and economic development. For instance, the production function would be expected to change in ways that reduce the advantages of slower population grown. We have reviewed considerable evidence, particularly in the agricultural sector, of how technology adapts to changes in factor proportions. In most places it is reasonable to expect slower growth in the labor force to reduce the intensity of adaptive response in the form of land improvement, instigation, and agricultural research. On the other hand, the calculation does not reflect increases in production due to the healthier and better educated work force Mat would result from lower fertility. Much more sophisticated models of production and fertility have been constructed with a variety of assumptions about the nature and intensity of relationships between economic and demograph* variables (see Ahlburg, 1985, for a thorough review). None of these models embodies the more

CONCLUSION 91 recent evidence on the nature and magnitude of effects that is included here, and we are not in a position to endorse any of the models. Careful scientific research is needed both to beuer quantify and to further elucidate most of the relationships discussed in this book. Research is especially needed on urbanization and the consequences of urban growth; savings and the formation of physical capital; the effect of population grown on health, education, and the development of human capital; and the nature and extent of extemalities of childbearing. Such research would be appropriately supported by mission-oriented development organizations as well as by basic research agencies. Whether the economic problems posed by population grown are large or small, and whether they are best approached by slowing the population grown rate, depends ultimately on the costs of alternative policy responses. We now turn to outline those responses. POLICY IMPLICATIONS: THE ROLE OF FAMILY PLANNING We have stressed that population growth can exacerbate the ill effects of a variety of inefficient policies, such as urban bias in the provision of infrastructure, direct and indirect food subsidies Hat distort agricultural markets, credit market distortions, and inadequate management of common property. A fundamental solution to these problems lies in better policies outside the population arena. However, some policies may be extremely resistant to correction, even over the medium to long term. Moreover, we have found some beneficial effects of slower population grown even in the presence of well-functioning markets and other institutions. Thus, there appears to be a legitimate role for population policy, providing its benefits exceed its costs. Although educational and health policies may have indirect effects on fertility, family planning programs have been the most conventional and direct instrument of government population policy. By family planning programs, we mean He provision of contraceptive services, together with information about contraception and child spacing. The total amount spent on family planning programs in 1982 was less than $2 billion, of which international assistance represents about $330 million (World Bank, 1984:148~. By companson, total official development assistance by Organization for Economic Cooperation and Development (OECD) countries was about $27.5 billion in 1983 Should Bank, 1984:252~. In most developing countries, family planning program expenditures represent less than 1 percent of the government budget. Government support for family planning programs can have an economic and social rationale quite apart from He effect of programs on rates of population growth. ~ many societies, individual control of reproduction

92 POPUlA77ON GROWIW AND ECONOMIC DEVELOPMENT is considered a basic human right, similar in nature to good health or literacy. Lack of information about reproduction services and other services may constrain parents from achieving the* desired number and spacing of children. In such a situation, the supply of information and services will increase family welfare. Govemments can often supply information and services about reproduction more efficiently and cheaply than Me private sector, in part because large and risky investments are required and because some of Me benefits to consumers cannot be captured by the suppliers. In particular, valuable information can flow from person to person without any financial reward to the initial supplier: information about the consequences of childbearing is one example; the rhythm method is another. In this case, the private sector will underinvest in the provision of such services. The rationale for government support for family planning programs is similar to that for support of a variety of public health programs, as well as for agricultural research and extension services. F~ermore, when health services are provided by government, an additional rationale for government family planning programs is that the services can be efficiently supplied by existing health pet sonnet (World Bank, 1984~. Finally, family planning programs are likely to be of more value to lower income groups than to higher income groups, who may have beKer access to private services, so government support for these programs can help to advance equity goals If people use the services and information supplied by government family planning programs and if fertility falls as a result, an obvious case can be made that the program has increased the private welfare of users by reducing the cost of fertility control and by reducing the gap between desired and achieved fertility. This gain in private well-being is added to whatever other gains accrue on the national agenda from fertility reduction. The large fertility declines that occ~d in such countries as Mexico, Indonesia, and Thailand during the 1970s~eclines that were associated over time with intensified national family planning programs-suggest that private welfare gains from such programs are large. The large amount of unwanted childbearing in developing countries Mat was revealed by the World Fertility Survey (Boulder, 1985) suggests that such programs have considerable remaining potential to increase private welfare and reduce population growth rates. When national economic and social goals can be furthered by a reduction in fertilibr, the fact that family planning programs can achieve such reductions while increasing the well-being of users of these services accounts for milch of their Inactiveness as a policy instrument for governments in developing countries. A similar att~veness applies to removal of legal prohibitions against access to means of ferdlity control, prohibitions that pose serious obstacles to couples, reproductive behavior in many counties (Berelson and Lieberson, l979~. In sum, there is little debate about the desirability of

CONCLUSION 93 programs Hat allow couples access to easy, affordable, and effective means of family planning, even among Hose who see population growth as a neuter or even a positive influence on development (Wattenberg and Zinsmeister, 1985). When a couple's childbearing decision imposes external costs on other families-in overexploitation of common resources, congestion of public services, or contribution to a socially undesirable distribution of income- a case may be made for policies that go "beyond family planning." Such policies include persuasive campaigns to change family size norms and combinations of incentives and taxes related to family size. It is more difficult to make the case for He imposition of drastic financial or legal restrictions on childbearing. As noted above, such restrictions are likely to entail large welfare losses at the individual level; these losses would be hard to assess quantitatively, as are the possible social benefits of such restrictions. Because economic development is a multifaceted process, no single policy or single-sector strategy can be successful by itself. Thus, family planning programs by themselves cannot make a poor county rich or even move it many notches higher on the scale of development. However, family planning programs that enable couples to have the number of children they desire increase the private welfare of the people who use Heir services while reducing He burden on society of whatever economic externalities exist. And family planning programs are likely to increase He well-being of the users' children and to extend rawer Han to restrict personal choices. Thus, family planning programs can play a role in improving the lives of people in developing counties.

This book addresses nine relevant questions: Will population growth reduce the growth rate of per capita income because it reduces the per capita availability of exhaustible resources? How about for renewable resources? Will population growth aggravate degradation of the natural environment? Does more rapid growth reduce worker output and consumption? Do rapid growth and greater density lead to productivity gains through scale economies and thereby raise per capita income? Will rapid population growth reduce per capita levels of education and health? Will it increase inequality of income distribution? Is it an important source of labor problems and city population absorption? And, finally, do the economic effects of population growth justify government programs to reduce fertility that go beyond the provision of family planning services?

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An Introduction to Population Growth

Why Study Population Growth?

Population ecology is the study of how populations — of plants, animals, and other organisms — change over time and space and interact with their environment. Populations are groups of organisms of the same species living in the same area at the same time. They are described by characteristics that include:

• population size: the number of individuals in the population
• population density: how many individuals are in a particular area
• population growth: how the size of the population is changing over time.

If population growth is just one of many population characteristics, what makes studying it so important?

First, studying how and why populations grow (or shrink!) helps scientists make better predictions about future changes in population sizes and growth rates. This is essential for answering questions in areas such as biodiversity conservation (e.g., the polar bear population is declining, but how quickly, and when will it be so small that the population is at risk for extinction?) and human population growth (e.g., how fast will the human population grow, and what does that mean for climate change, resource use, and biodiversity?).

Studying population growth also helps scientists understand what causes changes in population sizes and growth rates. For example, fisheries scientists know that some salmon populations are declining, but do not necessarily know why. Are salmon populations declining because they have been overfished by humans? Has salmon habitat disappeared? Have ocean temperatures changed causing fewer salmon to survive to maturity? Or, maybe even more likely, is it a combination of these things? If scientists do not understand what is causing the declines, it is much more difficult for them to do anything about it. And remember, learning what is probably not affecting a population can be as informative as learning what is.

Finally, studying population growth gives scientists insight into how organisms interact with each other and with their environments. This is especially meaningful when considering the potential impacts of climate change and other changes in environmental factors (how will populations respond to changing temperatures? To drought? Will one population prosper after another declines?).

Ok, studying population growth is important...where should we start?

Population Growth Basics and the American Bison

The US government, along with private landowners, began attempts to save the American bison from extinction by establishing protected herds in the late 1800's and early 1900's. The herds started small, but with plentiful resources and few predators, they grew quickly. The bison population in northern Yellowstone National Park (YNP) increased from 21 bison in 1902 to 250 in only 13 years (Figure 1, Gates et al . 2010).

The yearly increase in the northern YNP bison population between 1902 and 1915 can be described as exponential growth . A population that grows exponentially adds increasingly more individuals as the population size increases. The original adult bison mate and have calves, those calves grow into adults who have calves, and so on. This generates much faster growth than, say, adding a constant number of individuals to the population each year.

Exponential growth works by leveraging increases in population size, and does not require increases in population growth rates. The northern YNP bison herd grew at a relatively constant rate of 18% per year between 1902 and 1915 (Gates et al . 2010). This meant that the herd only added between 4 and 9 individuals in the first couple of years, but added closer to 50 individuals by 1914 when the population was larger and more individuals were reproducing. Speaking of reproduction, how often a species reproduces can affect how scientists describe population growth (see Figure 2 to learn more).

Figure 2: Bison young are born once a year — how does periodic reproduction affect how we describe population growth? The female bison in the YNP herd all have calves around the same time each year — in spring from April through the beginning of June (Jones et al. 2010) — so the population size does not increase gradually, but jumps up at calving time. This type of periodic reproduction is common in nature, and very different from animals like humans, who have babies throughout the year. When scientists want to describe the growth of populations that reproduce periodically, they use geometric growth. Geometric growth is similar to exponential growth because increases in the size of the population depend on the population size (more individuals having more offspring means faster growth!), but under geometric growth timing is important: geometric growth depends on the number of individuals in the population at the beginning of each breeding season. Exponential growth and geometric growth are similar enough that over longer periods of time, exponential growth can accurately describe changes in populations that reproduce periodically (like bison) as well as those that reproduce more constantly (like humans). Photo courtesy of Guimir via Wikimedia Commons.

The power of exponential growth is worth a closer look. If you started with a single bacterium that could double every hour, exponential growth would give you 281,474,977,000,000 bacteria in just 48 hours! The YNP bison population reached a maximum of 5000 animals in 2005 (Plumb et al . 2009), but if it had continued to grow exponentially as it did between 1902 and 1915 (18% growth rate), there would be over 1.3 billion (1,300,000,000) bison in the YNP herd today. That's more than thirteen times larger than the largest population ever thought to have roamed the entire plains region!

The potential results may seem fantastic, but exponential growth appears regularly in nature. When organisms enter novel habitats and have abundant resources, as is the case for invading agricultural pests, introduced species , or during carefully managed recoveries like the American bison, their populations often experience periods of exponential growth. In the case of introduced specie s or agricultural pests, exponential population growth can lead to dramatic environmental degradation and significant expenditures to control pest species (Figure 3).

After the Boom: Limits to Growing Out of Control

Let's think about the conditions that allowed the bison population to grow between 1902 and 1915. The total number of bison in the YNP herd could have changed because of births, deaths, immigration and emigration (immigration is individuals coming in from outside the population, emigration is individuals leaving to go elsewhere). The population was isolated, so no immigration or emigration occurred, meaning only births and deaths changed the size of the population. Because the population grew, there must have been more births than deaths, right? Right, but that is a simple way of telling a more complicated story. Births exceeded deaths in the northern YNP bison herd between 1902 and 1915, allowing the population to grow, but other factors such as the age structure of the population, characteristics of the species such as lifespan and fecundity , and favorable environmental conditions, determined how much and how fast.

Changes in the factors that once allowed a population to grow can explain why growth slows or even stops. Figure 4 shows periods of growth, as well as periods of decline, in the number of YNP bison between 1901 and 2008. Growth of the northern YNP bison herd has been limited by disease and predation, habitat loss and fragmentation, human intervention, and harsh winters (Gates et al . 2010, Plumb et al . 2009), resulting in a current population that typically falls between 2500 and 5000, well below the 1.3 billion bison that continued exponential growth could have generated.

Factors that enhance or limit population growth can be divided into two categories based on how each factor is affected by the number of individuals occupying a given area — or the population's density . As population size approaches the carrying capacity of the environment, the intensity of density-dependent factors increases. For example, competition for resources, predation, and rates of infection increase with population density and can eventually limit population size. Other factors, like pollution, seasonal weather extremes, and natural disasters — hurricanes, fires, droughts, floods, and volcanic eruptions — affect populations irrespective of their density, and can limit population growth simply by severely reducing the number of individuals in the population.

The idea that uninhibited exponential growth would eventually be limited was formalized in 1838 by mathematician Pierre-Francois Verhulst. While studying how resource availability might affect human population growth, Verhulst published an equation that limits exponential growth as the size of the population increases. Verhulst's equation is commonly referred to as the logistic equation , and was rediscovered and popularized in 1920 when Pearl and Reed used it to predict population growth in the United States. Figure 5 illustrates logistic growth: the population grows exponentially under certain conditions, as the northern YNP bison herd did between 1902 and 1915, but is limited as the population increases toward the carrying capacity of its environment. Check out the article by J. Vandermeer (2010) for a more detailed explanation of the equations that describe exponential and logistic growth.

Logistic growth is commonly observed in nature as well as in the laboratory (Figure 6), but ecologists have observed that the size of many populations fluctuates over time rather than remaining constant as logistic growth predicts. Fluctuating populations generally exhibit a period of population growth followed a period of population decline, followed by another period of population growth, followed by...you get the picture.

Populations can fluctuate because of seasonal or other regular environmental cycles (e.g., daily, lunar cycles), and will also sometimes fluctuate in response to density-dependent population growth factors. For example, Elton (1924) observed that snowshoe hare and lynx populations in Canadian boreal forests fluctuated over time in a fairly regular cycle (Figure 7). More importantly, they fluctuated, one after the other, in a predictable way: when the snowshoe hare population increased, the lynx population tended to rise (plentiful food for the lynx!); when the lynx population increased, the snowshoe hare population tended to fall (lots of predation on the hare!); when the snowshoe hare...(and the cycle continues).

It is also possible for populations to decline to extinction if changing conditions cause death rates to exceed birth rates by a large enough margin or for a long enough period of time. Native species are currently declining at unprecedented rates — one important reason why scientists study population ecology. On the other hand, as seen in the YNP bison population, if new habitats or resources are made available, a population that has been declining or relatively stable over a long period of time can experience a new phase of rapid, long-term growth.

What about Human Population Growth?

The growth of the global human population shown in Figure 8 appears exponential, but viewing population growth in different geographic regions shows that the human population is not growing the same everywhere. Some countries, particularly those in the developing world, are growing rapidly, but in other countries the human population is growing very slowly, or even contracting (Figure 9). Studying the characteristics of populations experiencing different rates of growth helps provide scientists and demographers with insight into the factors important for predicting future human population growth, but it is a complicated task: in addition to the density dependent and independent factors we discussed for the northern Yellowstone National Park bison and other organisms, human population growth is affected by cultural, economic, and social factors that determine not only how the population grows, but also the potential carrying capacity of the Earth.

biodiversity : The variety of types of organisms, habitats, and ecosystems on Earth or in a particular place.

exponential growth : Continuous increase or decrease in a population in which the rate of change is proportional to the number of individuals at any given time.

age structure : The distribution of individuals among age classes within a population.

lifespan : How long an individual lives, or how long individuals of a given species live on average .

fecundity : The rate at which an individual produces offspring.

density : Referring to a population, the number of individuals per unit area or volume; referring to a substance, the weight per unit volume.

carrying capacity : The number of individuals in a population that the resources of a habitat can support; the asymptote, or plateau, of the logistic and other sigmoid equations for population growth.

logistic equation : The mathematical expression for a particular sigmoid growth curve in which the percentage rate of increase decreases in linear fashion as the population size increases.

native species : A species that occurs in a particular region or ecosystem by natural processes, rather than by accidental or deliberate introduction by humans.

introduced species : A species that originated in a different region that becomes established in a new region, often due to deliberate or accidental release by humans.

demographers : Demography is the study of the age structure and growth rate of populations.

References and Recommended Reading

Dary, D. A. The Buffalo Book: The Full Saga of the American Animal . Chicago, IL: Swallow Press, 1989.

Elton, C. Periodic fluctuations in the numbers of animals: Their causes and effects. British Journal of Experimental Biology 2, 119-163 (1924).

Gates, C. C. et al . eds. American Bison: Status Survey and Conservation Guidelines 2010 . Gland, Switzerland: International Union for Conservation of Nature, 2010.

Hornaday, W. T. The Extermination of the American Bison, With a Sketch of its Discovery and Life History . Annual Report 1887. Washington, DC: Smithsonian Institution, 1889.

Jones, J. D. et al . Timing of parturition events in Yellowstone bison Bison bison : Implications for bison conservation and brucellosis transmission risk to cattle. Wildlife Biology 16, 333-339 (2010).

Livingston, M., Osteen, C. & Roberts, D. Regulating agricultural imports to keep out foreign pests and disease. United States Department of Agriculture, Economic Research Service. Amber Waves 6, " http://www.ers.usda.gov/AmberWaves/September08/Features/RegulatingAgImports.htm " (2008).

Pearl, R. & Reed, L. J. On the rate of growth of the population of the United States since 1790 and its mathematical representation. Proceedings of the National Academy of Sciences of the United States of America 6, 275-288 (1920).

Plumb, G. E. et al . Carrying capacity, migration, and dispersal in Yellowstone bison. Biological Conservation 142, 2377-2387 (2009).

Rohrbaugh, R., Lammertink, M. & Piorkowski, M. Final Report: 2007 - 08 Surveys for Ivory-Billed Woodpecker and Bird Counts in Louisiana . Ithaca, NY: Cornell Laboratory of Ornithology, 2009.

Shaw, J. H. How many bison originally populated western rangelands? Rangelands 17, 148-150 (1995).

Vandermeer, J. How Populations Grow: The Exponential and Logistic Equations. Nature Education Knowledge 1 (2010).

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Public Health and Overpopulation: The United Nations Takes Action

With the world’s population rising faster than ever before, will our population growth outpace our resource reserves? How can the dangerous effects of overpopulation be managed without diminishing the major improvements in our quality of life that come about thanks to population growth?

The UN projects that over half of the Earth’s population growth in the next three decades will occur in the continent of Africa. This is due to the fact that, from 2010 to 2015, Africa’s population grew at a rate of 2.55 percent annually, with the continent still maintaining the highest pace of population growth among other continents. The UN predicts that, behind Africa, Asia will be the second greatest donor to future international population growth, with an expected addition of approximately one billion people by 2050. In contrast, within every European nation, fertility rates are currently below the population replacement level, which is approximately two children per woman. In most of Europe, fertility rates have remained beneath replacement level for decades. The global population grew fourfold in the past 100 years, so what impact could increased population growth have in the future? Will there be mass-migration? Overcrowding in already densely populated or resource-rich areas? Poor living conditions and sanitation similar to Industrial Revolution era slums?

The global population is currently rising at a steady rate. The number of humans existing on Earth has never been as high as it is now. In 1800, Earth had approximately 1 billion inhabitants, which rose to 2.3 billion in 1940, then 3.7 billion in 1970, and approximately 7.5 billion today. In the last five decades, Earth has experienced an extreme population boom. This phenomenon is known as overpopulation, where the condition in which the amount of humans currently existing on Earth outstrips future resource availability and earth’s carrying capacity. Throughout human history, birth and death rates have always counterbalanced each other, which ensured that Earth had a maintainable population growth level. However, in the 1960s, the global population increased at an unparalleled rate. This brought about a variety of apocalyptic predictions, most prominently, a revival of the Malthusian trap panic.

Paul R. Ehrlich’s 1968 novel, The Population Bomb , eerily echoes Thomas R. Malthus’s landmark 1798 Essay on the Principle of Population . Ehrlich’s novel proposes theories regarding potential outcomes for when agricultural growth does not keep pace with population growth. Ultimately his theories say that the world’s food supply will inevitably become inadequate for feeding the general population, whose numbers would continue to swell until famine, disease epidemics, war, or other calamities took root. These Malthusian predictions about out-of-control population growth have resulted in a variety of detrimental global impacts, particularly the emergence of extreme reproductive control measures, which have taken center stage on an international scale. Today, despite the fact that population scientists mostly agree that Malthus’s forecasts were overblown, the lingering prevalence of these fears have contributed to millions of forced sterilizations in Mexico, Bolivia, Peru, Indonesia, Bangladesh and India, as well as China’s two-child policy . Overall, this has left many wondering whether extreme population growth projections are legitimate or merely groundless panic perpetuated by alarmists.

The Demographic Transition

In reality, rising birth rates and population booms are components of a four-step process called the demographic transition, which the Earth is currently undergoing. Most developed nations have already made this transition, but other countries are currently experiencing this change. In the 1700s, the entire world was undergoing the first stage of the demographic transition. During this time, the continent of Europe was in even poorer condition than the modern-day definition of a developing region, and was afflicted with inferior public health, sustenance, and medical facilities. Birth rates were higher; however, death rates were also higher. For this reason, population growth remained largely stagnant.

Statistically, in the 1700s, women birthed four to six children. However, on average, only two survived to adulthood. When the Industrial Revolution began in Great Britain in the mid-18th century, the Earth experienced the most significant shift in human lifestyles since the Agricultural Revolution. The Industrial Revolution altered every aspect of society, and fostered a greater sense of global interconnectedness. For example, many peasants became factory workers, manufactured products became widely available due to mass production, and countless scientific advancements improved existing methods of transportation, communication, and medicine.

Gradually, this economic development created a middle class and, after the work of union activists, ultimately raised the standard of living and health care for the impoverished labor demographic. Thus began the second transition stage. The increased availability of better foodstuffs, sanitation, and medicine directly contributed to lower death rates, causing a population explosion that doubled Great Britain’s population from 1750 to 1850. In the past, families tended to have more children because not all were expected to survive, but when child mortality rates decreased, the third transition stage was launched. This stage involves reduced conception rates and slowing population growth. Ultimately, a balance was established, with fewer deaths and births, creating a stable population growth rate and signifying the attainment of the fourth and final stage of the demographic transition.

Even as birth rates have decreased dramatically, Earth’s population is still rising at an alarming rate because the humans conceived during the population boom of the 1970s and 1980s are currently having more children; however, the current average number of children per family remains two and a half, while it was five during the late 1970s. As this generation ages and its fertility diminishes, the rate of population growth will likely continue to decrease in every nation. Most of the world’s countries have reached the fourth stage of the demographic transition. In approximately 80 years, developed countries will experience a reduction in fertility from over six children to fewer than three children. Malaysia and South Africa reached this point in 34 years, Bangladesh in 20 years,  and Iran in 10 years. If developing countries are afforded more support, they will reach this point much faster.

Overall, most scientists postulate that human population growth will eventually come to an end, and the UN predicts that Earth’s population will not exceed twelve billion. Some of the major causes of population growth are reduced infant mortality rates, increased lifespans, higher fertility rates, advances in science and technology, and improved access to proper medical care. With the UN’s continued assistance, concurrent with overpopulation, the development level of the global community will increase, and the number of people living in poverty will decrease. Nonetheless, an ever-expanding human population is an immense social and economic challenge that necessitates the alignment of different national interests, especially with regards to reproductive rights, resource availability, and environmental concerns.

The United Nations Takes Action

In 1969, the United Nations Population Fund (UNFPA) was established in order to lead the UN in implementing population programs fundamentally based on the notion of family planning, or the “human right of individuals and couples to freely determine the size of their families” without governmental interference or legislation. In 1994, at the International Conference on Population and Development in Cairo, Egypt, the designated objectives of the UNFPA were determined in greater depth. It was decided that the UNFPA would specifically focus on the gender and human rights elements of population issues; consequently, the UN Population Fund was granted the lead role in aiding nations in fulfilling the Conference’s Programme of Action.

The three most significant sections of the UN Population Fund mandate are “Reproductive Health,” “Gender Equality,” and “Population and Development.” The United Nations Population Division (UNPD) works to confront the interconnected global issues posed by population growth, which is primarily fueled by rising fertility rates, increased longevity, and greater international migration. The UN produces the official demographic approximations and predictions for every country and all regions of the world. The UNFPA specifically addresses global population by compiling data and statistics regarding migration, fertility, marriage, regional development, urbanization, world population projections, and national population policies.

In November 2012, the UNFPA declared family planning a global human right; however, approximately 12 percent of 15 to 49-year-old women internationally are not afforded access to family planning. This is considered an egregious modern-day human rights infringement. The UNFPA aids various UN bodies like the Commission on Population and Development, and endorses the implementation of the Programme of Action undertaken by the International Conference on Population and Development (IPCD) in 1994. The UNFPA has been successful in urging international cooperation on the issue of securing family planning as a human right, pushing the UN to hold three conferences concerning the issue of population, along with two special sessions of the General Assembly and a summit in 2019 .

The Way Forward

Ultimately, apocalyptic population growth fears are overblown, and as such, draconian population control regulations are unnecessary. We have witnessed progress on an international scale in this area, perhaps most notably with China revoking its infamous, longstanding one-child policy just seven years ago. However, a broader global focus on guaranteeing family planning as a human right remains essential. In the words of economist Julian Simon, “Whatever the rate of population growth is, historically it has been that the food supply increases at least as fast, if not faster.” Since Ehrlich’s initial fear-mongering regarding an overpopulation-​induced Armageddon, the planet’s population has more than doubled . However, annually, famine deaths have dropped by millions. Today’s famines are war-induced, not caused by natural resource consumption. As production rose, prices fell and calorie consumption increased, which decreased malnutrition worldwide. In Simon’s words, human ingenuity is the “ ultimate resource .” Therefore, the enactment of heavy-handed population-​control regulations is not only abhorrent, but is also irrational and unsupported by scientific evidence.

Sophia Scott

Sophia Scott is a staff writer for the Harvard International Review. She is interested in global health & health equity, along with the intersections between science and policy.

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Essay on Population Growth for Students and Children

500+ words essay on population growth.

There are currently 7.7 billion people on our planet. India itself has a population of 1.3 billion people. And the population of the world is rising steadily year on year. This increase in the population, i.e. the number of people inhabiting our planet is what we call population growth. In this essay on population growth, we will see the reasons and the effects of this phenomenon on our planet and our societies.

One important feature of population growth is that over the last century it has shown exponential growth. When the pattern of increase is by a fixed quantity, we call this linear growth, for example, 3, 5, 7, 9 and so on. Exponential growth shows an increase by a fixed percentage, for example, 2, 4, 8, 16, 32 and so on. This exponential growth is the reason our population has seen such an immense increase over the past century and a half.

Causes of Population Growth

To fully understand the phenomenon, in this essay on population growth we will discuss some of its causes. Understanding the reasons for such exponential growth will help us better understand how to plan for the future. So let us begin with one of the main causes, which is the decline in the mortality rate.

Over the last century, we have made some very significant and notable advancements in medicine, science, and technology. We have invented vaccines, found new treatments and even almost completely eradicated some life-threatening diseases. This means that people now have a much higher life expectancy than their ancestors.

Along with the decrease in mortality rate, these advancements in medicine and science have also boosted the birth rates. We now have ways to help those with infertility and reproductive problems. Hence, birth rates around the world have also seen massive improvements. This coupled with slowing mortality rates has caused overpopulation.

Often the lack of proper education is also stated as the culprit of rampant overpopulation. People around the world need to be made aware of the ill-effects of global overpopulation. Values of family planning and sustainable growth needs to be instilled not only in children but adults also. The lack of this awareness and education is one of the reasons for this growth in population.

Get the huge list of more than 500 Essay Topics and Ideas

Effects of Population Growth

This exponential population growth that our planet has experienced over the last 150 years has had some severe negative effects. The most obvious and common impact is that overpopulation has put a great strain on the natural resources of the earth. As we know, some of the resources available to us come in limited quantities, for example, fossil fuels. When the population explosion happened, these resources are becoming rarer and will one day run out completely.

The increased population had also lead to increased pollution and industrialization . This has adversely affected our natural environment leading to more health problems in the majority of the population. And as the population keeps growing, the poorer countries are running out of food and other resources causing famines and various such disasters.

And as we are currently noticing in India, overpopulation also leads to massive unemployment. Overall the economic and financial condition of densely populated regions deteriorates due to the population explosion.

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Global population growth and sustainable development.

Global Population Growth and Sustainable Development probes the linkages between global population growth and the social, economic and environmental dimensions of sustainable development. The report examines how the current rapid growth of the human population is a consequence of the demographic transition from high to low levels of mortality and fertility. The report reviews the connections between population growth and key aspects of social and economic development, including poverty, hunger and malnutrition, health, education, gender equality, economic growth and decent work. It also explores the contribution of global population increase to environmental degradation, including climate change. 

The report is part of a series on major demographic trends being published by the Population Division of the United Nations Department of Economic and Social Affairs. Reports in the series examine the complex relationships linking demographic processes to social and economic development and environmental change.      

• Full report
• Policy brief
• Key messages  
• Media advisory
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EFFECT OF POPULATION GROWTH ON ECONOMIC DEVELOPMENT: THE CASE OF INDIA

The population growth has a vital impact on economic development. India's population increased 235 percent over the year1951 to 2011. The relationship between population growth and economic growth is of great interest both for demographer and for development economists. There are generally three different types of views on how population affects the economic development of a nation. One, supporting the positive impact of population growth on economic development. Two, supporting the negative effect of population growth on economic development. Three, believe that population growth has no relation with economic development. It is widely accepted that any growth in the economic development needs human capital as its main weapon and the rise in population can act as a provider of human capital. Population growth is the real strength and power of a country like India. With higher population, we will have high labor force and this will help in creating labor diversity in the nation and in turn this higher population will also help for the rise in output of the nation. No doubt, this population rise can be disastrous if we don't use them properly. This paper is an attempt to show how rising population of India can increase economic development of the country.

Related Papers

Indus Foundation International Journals UGC Approved

Persons are resources as well as split ends of economic development. They are an asset if in ample strength and prove to be a burden if excess in strength. Population has traversed the optimal limit in India and has grown to be a liability. Overpopulation has been major dilemma in India. The efforts to remove the nuisance of population problem have only been partially effective. In significance the rate of population increase has gone down, but the sense of balance between the optimum population growth and a healthy nation is far to be attained. Unhealthy living, lack of knowledge, illiteracy, and lack of appropriate recreation have remained the basis of population trouble in India. The chief endeavor of this effort is to stumble on the effects of hasty population growth on economic development of India. This is very important because India is second most populated country in the world and many studies show that India will leave behind china soon based on the population growth rate in both of these countries. So the study of relationship between these variables may help the government to think about the effect of population growth on their policies in upcoming or future.

Kala Sarovar

Dr. G. YOGANANDHAM

The world's population is growing by 83 million people year, and 57 billionaires control 70% of the nation's wealth. According to the medium-variant prediction, there will be 8.6 billion people on the planet in 2030, 9.8 billion in 2050, and 11.2 billion in 2100. Population expansion has a negative influence on the economy, increasing costs and lowering savings, which causes hardship for the working and middle classes.A major contributor to poverty in developing countries is overpopulation, which also contributes to unemployment, food shortages, low per capita income, problems with capital formation, high levels of pressure, social problems, economic insecurity, social insecurity, increased environmental pressure, and societal instability. Overcrowding, poverty, crime, pollution, and political upheaval are all effects of India's population increase, which has also resulted in overuse and loss of fertile land. In order to support human flourishing in a globalised world, this study offers a theoretical assessment of the process for population expansion and Indian economic development. There are a number of major issues that India is dealing with, including overcrowding, which has decreased as a result of government initiatives. Strong legislation and regulatory measures must be implemented to address this in order to make the best use of the resources at hand and transform the nation's human resources into priceless assets. Using secondary sources that include data and information pertinent to the study's problem, this research is descriptive and is theoretically grounded. From a theoretical perspective, it is both a descriptive and diagnostic design.In order to promote human flourishing in a globalised society, this article analyses population increase and Indian economic development.This study tries to assess the population increase and Indian economic development processes in relation to poverty, inequality, resource scarcity, and unemployment.

Economic and Political Weekly, Vol - XXX No. 36 (Special Article)

Manashi Ray

India is the second most populous country in the world with 934 million people and according to estimates, it will grow to 1.4 billion by 2030. However population growth is not simply a problem of numbers; it is a problem of human welfare and development. This paper contends that population growth is not the only, or even the primary, source of low levels of living, eroding self esteem and limited freedom in the less developed nations. Contrary to customary assumptions, population growth in conjunction with other determinants of development has on many instances promoted social change, and in the recent past has been a boon to economic growth in the newly industrialised countries. It is therefore an issue of management and optimum utilisation of present and future human resources.

dev kothari

The present analysis assesses the implications of massive and rapid population growth for the Prime Minister Narendra Modi’s development goal, reflected in his poll slogan, “Sabka Saath, Sabka Vikas” (together with all, development for all). It is because population growth shares complex ties to poverty and inequality, exacerbating the gap between the rich and the poor, and creating obstacles in achieving an inclusive development.

Tanima Choudhuri

srinivas apr

The second most populous country, India, accounts for 17 percent of world population on 2.4% of the world surface area. Annual population growth of India is one percent of its total population. The paper talks of controlling population by various methods but mostly child birth. The paper talks of a family's economic situation to be responsible for child bearing. The paper talks of a time bound approach to improved productivity and its relation to personnel health and family health.

Quest Journal of Management and Social Sciences

Quest Journal of Management and Social Sciences , Deboshmita B.

Background: The relationship between population and economic growth has always been a subject of debate. There has never been any clear consensus amongst economists about the nature and extent of influence that population has on the economic growth of a country. Objective: This paper aims to explore the influence exerted by the age structure of the population on the economic growth of a country. Method: The paper uses secondary data to find the relation between Gross Domestic Product (GDP) per capita levels of countries and their respective Age Dependency Ratio. Result: There is a significant negative relationship between them, which implies that, if a country has a rise in a high proportion of the dependent population, per capita income will tend to be lower. Conclusion: The paper then makes a special study of the prospect of demographic dividend in India. The country is in the third phase of demographic transition, implying that the proportion of the working-age population is greater than the dependent population. This provides an ideal condition for the Government to reap the benefits of demographic dividend and achieve higher levels of economic growth.

Biswajit Ghosh

Padarabinda Rath

Olorunfemi Y Alimi

The precise relationship between population growth and per capita income has been inconclusive in the literature and the nexus has been found not clearly explain the determinants of rapid population growth in developing countries that lacks fertility control and management framework. This forms the rationale for this study to access the trend of factors that influence rapid population growth in developing countries between 1980 and 2010. This paper examined the comparative trend review of population growth determinants between developing countries (Bangladesh, Ethiopia, Indonesia, Mexico and Nigeria) and developed nations (Germany and United States). The trend analysis revealed that fertility rate, crude death rate, birth rate, mortality rate, and life expectancy are the major determinants of rapid population growth rate, while youth dependency ratio of young people below age 15 has also been attributed as one of the leading causes of population growth and growth threat in developin...

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Distinctive field effects of smoking and lung cancer case-control status on bronchial basal cell growth and signaling

• Olsida Zefi 1 , 2 ,
• Spencer Waldman 1 , 2 , 3 ,
• Ava Marsh 3 ,
• Miao Kevin Shi 3 ,
• Yosef Sonbolian 1 , 2 ,
• Batbayar Khulan 3 ,
• Taha Siddiqui 3 ,
• Aditi Desai 3 ,
• Dhruv Patel 3 ,
• Aham Okorozo 3 ,
• Samer Khader 3 ,
• Jay Dobkin 3 ,
• Ali Sadoughi 3 ,
• Chirag Shah 3 ,
• Simon Spivack 3   na1 &
• Yakov Peter 1 , 2 , 3 , 4   na1  

Respiratory Research volume  25 , Article number:  317 ( 2024 ) Cite this article

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Basal cells (BCs) are bronchial progenitor/stem cells that can regenerate injured airway that, in smokers, may undergo malignant transformation. As a model for early stages of lung carcinogenesis, we set out to characterize cytologically normal BC outgrowths from never-smokers and ever-smokers without cancers (controls) , as well as from the normal epithelial “field” of ever-smokers with anatomically remote cancers, including lung adenocarcinoma (LUAD) and squamous cell carcinoma (LUSC) (cases) .

Primary BCs were cultured and expanded from endobronchial brushings taken remote from the site of clinical or visible lesions/tumors. Donor subgroups were tested for growth, morphology, and underlying molecular features by qRT-PCR, RNAseq, flow cytometry, immunofluorescence, and immunoblot.

(a) the BC population includes epithelial cell adhesion molecule (EpCAM) positive and negative cell subsets; (b) smoking reduced overall BC proliferation corresponding with a 2.6-fold reduction in the EpCAM pos /ITGA6 pos /CD24 pos stem cell fraction; (c) LUSC donor cells demonstrated up to 2.8-fold increase in dysmorphic BCs; and (d) cells procured from LUAD patients displayed increased proliferation and S-phase cell cycle fractions. These differences corresponded with: (i) disparate NOTCH1 / NOTCH2 transcript expression and altered expression of potential downstream (ii) E-cadherin ( CDH1 ), tumor protein-63 ( TP63 ), secretoglobin family 1a member 1 ( SCGB1A1 ), and Hairy/enhancer-of-split related with YRPW motif 1 ( HEY1 ); and (iii) reduced EPCAM and increased NK2 homeobox-1 ( NKX2-1 ) mRNA expression in LUAD donor BCs.

Conclusions

These and other findings demonstrate impacts of donor age, smoking, and lung cancer case-control status on BC phenotypic and molecular traits and may suggest Notch signaling pathway deregulation during early human lung cancer pathogenesis.

Introduction

Lung cancer is the fourth most common cancer and the leading cause of cancer deaths worldwide. Smoking-related non-small cell lung cancer (NSCLC) accounts for over 80% of all lung cancers. NSCLC types include lung adenocarcinoma (LUAD) and squamous cell carcinoma (LUSC) which arise from cells of distinct origin and are characterized by different morphological and molecular properties [ 1 ].

Basal cells (BCs) are a class of stem/progenitors of the tracheal and bronchial airways that can replenish and repair injured or denuded epithelium [ 2 , 3 ]. Although a fairly heterogenic subset [ 4 , 5 ], canonical BC lineage markers include putative stem cell, squamous, and epithelial proteins, including adhesion molecule (EpCAM/CD326), TP63, cytokeratins, integrin α6 (ITGA6/CD49f), nerve growth factor receptor (NGFR) and podoplanin (PDPN), with a reported population of clonogenic and unrestricted LUSC and LUAD cancer stem cells co-expressing the CD24 protein [ 6 , 7 , 8 , 9 ]. Notch pathway specificity and downstream signaling, which include genes such as Hairy/enhancerofsplit related with YRPW motif 1 ( HEY1 ), and secretoglobin family 1 A member 1 (SCGB1A1) , have also been shown to play important roles in BC differentiation, proliferation, and carcinogenesis [ 10 , 11 ]. In NSCLC, NOTCH1 is considered to promote and NOTCH2 mediated-transduction to inhibit tumor growth and progression [ 11 , 12 ].

Increasing in a step-wise fashion with age and cigarette smoke, healthy BCs can acquire progressive cellular and genomic aberrations to transform into LUSC and LUAD tumor-initiating cells [ 13 , 14 ]. Genomic and cellular mutations in “epithelial field” BCs, far removed from any primary tumor, may explain the development of secondary synchronous or metachronous lesions in situ and may display progressive programs of lung cancer development [ 15 , 16 , 17 ]. To date, understanding of the earliest events that drive carcinogenesis in niches of the broad epithelial field remain incomplete.

In this study, we set out to evaluate long-term smoking influences on cytologically normal BCs in the cancer field, considering potential contributions of age and smoking dose. Morphological, proliferative, and Notch-related gene expressional changes that precede lung cancer were investigated. As BCs may ostensibly transform into tumors, understanding early incremental changes and a role for Notch signaling in these (cancer) stem cells may help pave the way to improved lung cancer risk prediction, detection, and a next generation of preventive therapies.

Materials and methods

Donor recruitment and biopsies.

Endobronchial brushings were collected from sites contralateral, or remote (> 5 cm) from any suspected cancer lesion or other known pathology, under an Einstein-Montefiore IRB approved protocol. Patient data including age, tobacco smoking history (pack-years), and other information were collected by standard face-to-face research coordinator interview pre-procedure, and electronic medical record chart verification. The final pathologic, bronchoscopic, and if relevant subsequent surgical procedure diagnoses were available after operation, per clinical routine and IRB approval. NSCLC types studied included LUAD and LUSC which arise from cells of distinct origin and are characterized by different morphological and molecular properties [ 1 ].

Cell culture

BCs were harvested from brush-exfoliated bronchial epithelium and cultured according to a previously reported culture/selection protocol [ 18 ]. In brief, bronchial cytologic brushes taken from white-light normal areas, were immersed into BEGM media supplemented with growth factors (Lonza, Morris Township NJ) and incubated at 37 °C in a 5% CO 2 incubator with media changed every other day. This method was reported to result in a pure culture of airway basal cells by day 7 in culture [ 19 ], with studied cells expressing TP63, KRT14, KRT5, podoplanin ( PDPN ), and nerve factor growth factor receptor ( NGFR ) BC lineage markers (Supplemental Fig.  1 ). All experiments were conducted on patient cells of low Passage (2–4), with individual figures representing donor subgroups from each category.

Gene expression

Quantitative Reverse Transcription Polymerase Chain Reaction (qRT-PCR) was performed as previously reported [ 20 ]. In brief, RNA was purified using RNeasy (Qiagen, Valencia, CA) and first-strand cDNA synthesis was performed using SuperScript IV (Life Technologies). Conventional PCR reactions were performed using SYBR green in a QuantStudio 3 thermocycler system (Life Technologies). qRT-PCR primer sequences can be found in Supplemental Table 1 . Relative changes in gene expression (to glyceraldehyde 3-phosphate dehydrogenase, GAPDH ) are provided as -dCt (directly correlating with the observed expression changes) or 2 −ΔΔCt (fold difference to never smokers) [ 18 ].

RNA sequencing : RNA seq expression data was extracted from 39 donors at dbGAP (accession number: phs003317.v1.p1). Initial fastq files were trimmed of flanking adapter sequences using trim galore ( https://github.com/FelixKrueger/TrimGalore/issues/25 ); the resulting fastq files were aligned to the human genome (hg38) using the splice-aware aligner STAR ( https://www.ncbi.nlm.nih.gov/pubmed/23104886 ). Directional read counts were obtained using htseq-count with parameter stranded set to reverse ( https://htseq.readthedocs.io/en/release_0.11.1/count.html ). RNA count reads for individual genes were normalized by total count of reads.

Immunofluorescence

Cells were grown on a coverslip, rinsed, fixed in 1% paraformaldehyde, and labeled with mouse anti-keratin 14, keratin 5, E-cadherin/CDH1, N-cadherin/CDH2, EpCAM (Invitrogen, Eugene OR); rabbit anti-TP63 (Santa Cruz Biotechnology, Santa Cruz CA), CCND1, NKX2-1 (Invitrogen), and/or goat anti-vimentin (Sigma -Aldrich, St Louis MO), washed and treated with either goat anti-mouse or goat anti-rabbit Alexa Flour 488 or 568, and/or Donkey anti-goat Alexa Fluor 488 (Invitrogen). DAPI (4’6-diamidino-2-phenylindole; Sigma-Aldrich) was applied and cells were covered with Fluoromount-G (Southern Biotech, Birmingham AL). Cell Nuclear morphology/morphometry , the fraction of spindle shaped or Click –iT EdU Alexa Fluor 488 (Invitrogen) positive cells were captured under identical exposures using a motorized Axio Imager M2 with apotome system (Zeiss, Germany) and analyzed in Fiji [ 21 ]. Data counts were performed by two independent observers blinded to patient diagnosis.

Western blots were performed as previously reported [ 22 ]. In brief, cells were rinsed, solubilized, sheared and protein concentrations determined (DC Protein Assay, Bio-Rad, Hercules, CA). 30 ug of protein was loaded and electrophoresed in SDS-polyacrylamide gels (Pierce, Rockford, IL), transferred onto polyvinylidene fluoride membranes (Millipore), and probed overnight at 4 °C. Primary antibodies included mouse anti-human ACTB (1:1,000), EpCAM (1:500); Rabbit anti-human NKX2-1 (1:1000), and Goat anti-VIM (1:500). Goat anti-mouse, donkey anti-rabbit or anti-goat horseradish peroxidase secondary antibodies were used (1:10,000; Bio-Rad). Protein detection was performed using a ChemiDoc imaging system (Bio-Rad). Signal intensities were normalized to ACTB.

Flow cytometry and FACS analyses

All experiments were performed as previously published by our laboratory [ 23 ]. Briefly, cells were dissociated, washed, and treated with: Alexa Fluor 488 conjugated rat anti-human/mouse CD49f/ITGA6 (Biolegend, San Diego CA) and CD271 (eBioscience), phycoerythrin (PE) conjugated mouse anti-human CD326/EpCAM (Biolegend) and podoplanin (BD Biosciences), and Allophycocyanin (APC) or peridinin-chlorophyll-protein (Per-CP) conjugated mouse anti-human CD24 (Invitrogen). For cell cycling analysis we used the Click –iT Plus EdU Alexa Fluor 488 Flow cytometry assay kit (Invitrogen) according to manufacturer’s instructions. Acquisition was performed on an Attune NxT flow cytometer (Thermofisher) or a FACSAria III (BD Biosciences). All analyses were performed using FlowJo software (BD Biosciences, Franklin Lakes NJ).

Statistical analysis

Experimental data was examined for normal (Gaussian) distribution by normality tests with T-test and ANOVA performed on normally distributed and Mann-Whitney U and Kruskal-Wallis conducted on nonparametric skewed data using Jamovi [ 24 ] with a p -value cutoff set at 0.05. At least two technical/biological replicates were performed on each studied sample. Unless indicated otherwise, data are presented as median and quartiles.”

Patient study information and BC characteristics

General patient data was collected concomitant with each bronchoscopic sample (Table  1 ). The following groups were included in the study: (1) Never-smoking/non-cancer controls; (2) Current or former smokers/non-cancer controls; (3) LUAD cases; and (4) LUSC cases. The average age (± SD) of the total never smoking population was 58.0 ± 15.6 years and significantly lower than the other groups (smoker 66.0 ± 12.6; LUAD 68.5 ± 10.6; LUSC 69.8 ± 10.1; n  ≥ 21; P  < 0.05 for all). The fraction of smokers (former and current) among cancer cases was 89% (24/27) in LUAD and 95% (20/21) in those patients diagnosed with LUSC ( P  < 0.001). Initial cytopathological analysis to confirm BC lineage and non-malignant phenotype of the acquired cells was performed, with 86% (12/14) of collected BCs characterized as benign and 14% (2/14) as atypical. Morphologically, none of the assessed cells from cases could be classified as malignant.

Contrasting proliferative rates and S-phase transition among donor patient BCs

As stem cells of the lung, we initially followed BC growth over a period of two weeks in culture (Fig.  1 A). In this experiment, we observed accelerated LUAD donor cell growth manifested as over a 3-fold higher cell count at day 10 than all other groups; with (never smoker) 0.9 ± 0.5 × 10 5 , (smoker) 0.5 ± 0.4 × 10 5 , (LUAD) 3.2 ± 1.0 × 10 5 , and (LUSC) 0.6 ± 0.2 × 10 5 . At day 14, never smoker and LUSC donor cell numbers reach those of LUAD, with the number of procured smoker cells at this day remaining significantly low ( n  ≥ 4; P  < 0.05).

Reduced smoker and enhanced LUAD donor BC proliferation. (A) BC counts over time in culture. LUAD cell numbers were significantly higher at day 10, and smoker cells lower at day 14. Data are presented as mean ± SEM ( n  ≥ 5; P  < 0.05 for both by ANOVA). (B) Box and whisker plots showing differences in the fraction of EdU incorporating nuclei comparing control (never smoker and smoker) and cases (LUAD and LUSC) cells at day-7 ( n  ≥ 5, ** P  < 0.01 by T-test); (C) Representative immunofluorescent micrographs depicting cycling EdU-positive (green) and negative (DAPI-stained; blue) nuclei in BCs from the four groups. (D) Box and whisker plots showing percent of EdU incorporating nuclei from the studied groups in C (median and quartiles; n  ≥ 5; * P  < 0.05 and ** P  < 0.01 by ANOVA and T-test comparing controls and cases, respectively). (E) Representative flow cytometry dot-plots of cells treated with EdU for 1.5 h and counterstained with 7-AAD. Cells in the G0/G1-phase can be seen within the bottom left box; S-phase cells in the top elongated box, and G2/M in the bottom right box. (F) Median and quartiles of cells in the S-phase of the cell cycle from panel E by group ( n  ≥ 5; * P  < 0.05 and ** P  < 0.01 by ANOVA). Passage 2 never-smoker (Never) and smoker controls, and lung adenocarcinoma (LUAD), and squamous cell carcinoma (LUSC) cells were used in these experiments. Scale bar = 20 μm

To validate cell growth differences, we compared DNA replication by measuring uptake of the DNA thymidine analogue 5’ethynyl-2’-deoyuridine (EdU) across the groups. Immunofluorescence of EdU uptake at day 7 in vitro demonstrated over a two-fold increase of labeled cells in lung cancer-case donor BCs (LUAD + LUSC; 33.1 ± 22.5%) as compared to non-cancer (never smoker + smoker; 14.0 ± 12.9%) ( n  ≥ 5, P  < 0.01; Fig.  1 B). As expected, this effect seemed to be driven by a > 2-fold increase in replicating LUAD donor cells compared to non-cancer donors (never smoker − 15.8 ± 12.8%; smoker − 12.1 ± 13.9%; LUAD − 40.4.1 ± 29.8%; LUSC − 24.9 ± 15.9%; Fig.  1 C and D ; n  ≥ 5; P  < 0.05). We next analyzed the cell cycle distribution of the groups by flow cytometry. While no major differences were observed in the sub-G, G0/G1, G2, and M phases of the cell cycle, a significantly increased proportion of LUAD donor cells were found in the S phase (never smoker − 14.1 + 10.5%; smoker − 17.3 + 12.2%; LUAD − 29.9 + 8.0%; and LUSC − 13.7 + 12.5%; Fig.  1 E and F ; n  ≥ 5; P  < 0.05). These findings indicate reduced BC growth in smokers and the accelerated proliferation of LUAD donor cells, which may correspond with a defective G1/S-phase checkpoint.

ITGA6 positivity and reduction of the EpCAM pos /ITGA6 pos /CD24 pos stem cell fraction in smoker BCs

To identify clonogenic cells of the selected population, we sorted BCs for EpCAM, ITGA6, and CD24 surface markers. Within the BC population two epithelial subgroups were identified, those positive for EpCAM (over 57%), and the remainder, negative for this pan-epithelial marker (Fig.  2 A). Within this population the percentage of the EpCAM pos /ITGA6 pos /CD24 pos (triple positive) clonogenic cells displayed a marked decrease from 32.4 ± 30.0% in never-smokers to 12.3 ± 12.0% in ever smokers ( n  ≥ 6; P  < 0.05; Fig.  2 A and B ). There was an increase in the percentage of ITGA6 decorated BCs in never, compared to former and current smoker groups combined ( n  ≥ 6; P  < 0.05), driven intriguingly by lower surface ITGA6 expression in former smokers (43.6 ± 27.8%) as compared to never- and current-smokers (73.8 ± 18.7% and 80.9 ± 18.7%, respectively; n  ≥ 5; P  < 0.05; Fig.  2 C and D). ITGA6 cell positivity was also lower in former smokers with patient smoking pack years to imply a distinct cellular identity found in former smokers ( n  ≥ 6; P  < 0.05; Fig.  2 E). No major differences in the overall proportion of EpCAM, ITGA6, and CD24 triple positive expression was observed between the non-cancer and cancer groups (Supplemental Fig.  2 ).

Reduction in EpCAM pos /ITGA6 pos /CD24 pos stem cell and ITGA6 pos fractions of donor smoker BC groups. (A) Smoking reduces the fraction of EpCAM/ITGA6/CD24 triple-positive stem cells in the BC population. Representative dot plots demonstrating data from never-smokers (top) and smokers (bottom). From left to right: isotype control, representative EpCAM and ITGA6 staining, and histogram depicting the CD24 pos subset from the EpCAM pos /ITGA6 pos (upper right) populational quadrant. Note, that the homogenous cellular population differs by EpCAM (epithelial) marker expression. (B) Box and whisker plots depicting triple positive, EpCAM pos /ITGA6 pos /CD24 pos fractions in the BC population of never and ever smokers. Differences between never and ever smokers are statistically significant for the triple positive population ( n  ≥ 6; * P  < 0.05 by T-test). (C) Representative histograms illustrating the percent of ITGA6 positive cells in never, former, and current smokers. transparent–unstained; light grey – isotype control; dark grey- ITGA6 labeled cells. (D) Box and whisker plots depicting median and quartiles of the percentage of ITGA6 labeled donor BCs with, intriguingly, never and current smokers exhibiting higher ITGA6 membrane expression than former smokers ( n  ≥ 6; * P  < 0.05 by ANOVA). (E) Scatterplot depicting a significant reduction in the percentage of ITGA6 expressing donor BCs from former smokers by patient pack-years. No differences were found in the fraction of EpCAM expressing cells. Color-coded regression lines ± SD (center) and boxplots for each parameter are shown on the margins ( n  ≥ 6; * P  < 0.05 by ANOVA). Passage 2 and 3 never smoker (Never), smoker, lung adenocarcinoma (LUAD), and squamous cell carcinoma (LUSC) cells were used in these experiments

Varying morphological, morphometric, and mesenchymal properties among cancer BCs

To better understand distinct BC fractions we studied morphological differences among the groups, with the proportion of cells with an elongated/spindle shape evident among donor-LUSC BCs. As compared to never smokers and smokers, LUSC donors displayed > 2.5-fold increase in spindle-shaped BCs with a more modest increase compared to LUAD cells, which reached statistical significance when accounting for patient smoking pack years ( n  ≥ 3; P  < 0.05; Fig.  3 A). The percentage of elongated cells by group were 5.4 ± 1.7% (never smoker), 5.1 ± 1.4% (smoker), 10.0 ± 2.3% (LUAD), and 14.3 ± 2.9% (LUSC). To test if the spindled phenotype might represent epithelial to mesenchymal transition (EMT), we stained for the intermediate filament protein vimentin (VIM), a canonical marker of EMT, and the mesenchymal lineage protein CDH2. VIM and to a lesser extent CDH2 labeling could be better detected in a larger proportion of LUSC-donor cells to suggest an increased mesenchymal tendency for this group (Fig.  3 B, and Fig.  4 ). Labeling cells for cytokeratin-14 (KRT14) clearly defined the spindle morphology, while the proliferative protein, cyclin-D1 (CCND1) demonstrated both nuclear and cytoplasmic localization in LUSC-donor cells, previously reported to indicate a cellular migratory and invasive state [ 25 ]. Performing nuclear morphometry using the DNA minor groove binding dye DAPI, while we found no differences in chromatin compaction (derived from the mean nuclear gray intensity of the same images [ 26 ]) the average nuclear area of LUAD donor cells was determined to be ≥ 24% larger than all other groups, in (never smoker) 111.0 ± 38.0, (smoker) 123.0 ± 31.5, (LUAD) 153 ± 21.8, and (LUSC) 92.1 ± 42.4 micron 2 , ( n  ≥ 4 for each group; P  < 0.05; Supplemental Fig.  3 ). Previously, nuclear size was reported to increase with transition from benign to carcinoma cells [ 27 ]. These data establish distinct cancer-related BC phenotypes manifested as mesenchymal (donor-LUSC) and proliferative (donor-LUAD) subset properties.

Elevated presence of dysmorphic cells with spindle phenotype in BCs from donor LUSC patients. (A) Median and quartiles showing the percentage of spindled cells in all four groups as quantified by two independent double blinded individuals. Data from passage 2 never-smoker (Never), smoker, lung adenocarcinoma (LUAD), and squamous cell carcinoma (LUSC) cells are shown ( n  ≥ 3; * P  < 0.05 by ANOVA). (B) Immunofluorescent micrographs from never smoker and lung squamous cell carcinoma (LUSC) patient cultured cells, labeled from left to right with; Top : DAPI nuclear counterstain (blue), vimentin (VIM; green) and N-cadherin (CDH2; red), and merge. Below : BCs from separate never and LUSC patients labeled from left to right with; DAPI (blue), cyclin D1 (CCND1; green) and cytokeratin 14 (KRT14; red), and merge. Labeling in cells from donor smokers and LUAD did not differ significantly from never smokers

Epithelial and mesenchymal gene expression properties differ among BC groups. (A) normalized RNA count (nRNAc) and (B) relative protein levels (rPL) of the intermediate filament gene vimentin (VIM), the epithelial cellular adhesion molecule (EpCAM), and the stem cell gene transcription termination factor (NKX2-1) between BCs from the different groups (normalized to b-actin; ACTB). Violin plots are shown ( n  ≥ 3). (C) Representative immunoblots depicting protein expression within the BC groups. Note the presence of multiple VIM bands in cells from smokers and cases (LUAD, LUSC). (D) Representative micrographs of cells harvested, cultured, and prepared for immunofluorescence demonstrating abnormal cytoplasmic NKX2-1 expression in smokers and the presence of nuclear EpCAM expression in LUAD BCs. Distinct labeling patterns between individual cells of the same group may emphasize populational diversity. From left to right; DAPI nuclear counterstain (grey), VIM (green), EpCAM (red), NKX2-1 (blue) and merge. Passage 2 never-smokers (Never), smokers, lung adenocarcinoma (LUAD), and lung squamous cell carcinoma (LUSC) cells were tested. ( n  ≥ 3)

Differential gene expression and protein localization correspond with differing BC growth characteristics

To better understand BC growth and transitional phases, we tested the expression and distribution of EpCAM and VIM in reference to the stem cell proliferation and differentiation and LUAD pathological biomarker homeobox-containing transcription termination factor (TTF1/NKX2-1) [ 28 ]. As demonstrated in Fig.  4 A, EPCAM and NKX2-1 expression differed between the groups, with LUSC donor cells displaying over a 2.8-fold reduction in normalized NKX2-1 transcript levels of 8.9 ± 6.2 for LUSC as compared to 56.4 ± 12.1, 25.0 ± 14.4, and 54.7 ± 18.5 in never smoker, smoker, and LUAD cells respectively (mean ± SEM; n  ≥ 3; P  < 0.05). While immunoblot did not show significant differences in relative protein quantities (normalized to ACTB; n  ≥ 3; Fig.  4 B), VIM expression demonstrated distinct molecular bands in donor smoker and cancer cells suggesting the presence of additional variants and/or modifications ( n  ≥ 3; Fig.  4 C). Immunofluorescence experiments corroborated expression differences among the groups, with enhanced EpCAM nuclear localization in LUAD donor cells ( n  = 3; Fig.  4 D ) . Of note, while most cells were positive for two of the above three markers by immunofluorescence, a select cellular fraction was observed to express all three proteins to strengthen transitional properties of the studied cells.

Distinct notch-related gene expression patterns in cancer, ageing, and smoker BCs

We next set out to determine if the observed differences in gene expression could be influenced by age and smoking pack years. As shown in Fig.  5 A, normalized gene counts of CDH1 , TP63 , SCGB1A1 and the Notch downstream mediator, HEY1 , all significantly declined with age ( n  ≥ 3; P  < 0.05). To determine if the reduction in gene expression with age was dependent on group, we repeated this experiment on individual qRT-PCR samples and plotted the results by group. While the trend of TP63 , SCGB1A1 , and HEY1 transcripts decreased with age independent of group, the reduction in CDH1 levels was perturbed in cells from donor-smoking and cancer-patients (Fig.  5 B; n  ≥ 4; P  < 0.05).

BC gene expression level changes with age can be disrupted by smoking and cancer. Scatterplots depicting the relationship between gene expression, age, and patient group in Passage 3 cells. (A) CDH1 , TP63 , SCGB1A1 , and HEY1 transcript levels decrease with age when pooling normalized gene counts of all groups. (B) Correcting for examined groups, in comparison to a decline in never smoker levels of CDH1 , expression remains flat in smokers and cancer cases as indicated by patient BC cycle threshold (portrayed as negative, -Ct; normalized to GAPDH ). Patient data points, regression line, and standard error of the mean (shaded and in respective colors), as well as parameter boxplots are shown. Never-smokers (Never), smokers, lung adenocarcinoma (LUAD), and lung squamous cell carcinoma (LUSC); n  ≥ 3;* P  < 0.05 and ** P  < 0.01

Plotting selected gene expression with smoking behavior among the pooled groups, only normalized NKX2-1 expression levels declined with pack years. In contrast, between never and ever smokers, gene expression of SCGB1A1 , the immune checkpoint, CD274 , and Notch pathway genes, NOTCH2 and HEY1 significantly decreased, while normalized KRT14 transcript levels increased in ever smokers with pack years by an average difference of ≥ 2 dCt values (Fig.  6 A and B; n  ≥ 5; P  < 0.05 for all). When comparing expression in never, former, and current smokers with pack years, while KRT14 , was significantly higher in the current smoker group, NOTCH1 and HES1 gene levels were reduced in current smokers by an average difference of ≥ 1.5 and ≥ 2.5 dCt values, respectively (Fig.  6 A and B; n  ≥ 5; P  < 0.05). Differences in Notch pathway gene expression is not surprising as Notch signaling was shown to regulate BC differentiation and proliferation and promote EMT during oncogenic transformation [ 29 , 30 , 31 ]. Indeed, performing pairwise correlation analyses between the pooled groups for selected Notch signaling transcripts with candidate S-phase cell division cyclin, cancer proto-oncogenes, and BC lineage markers, we found that while NOTCH1 and 3 expression were significantly associated with HEY1 in never smoker donor cells, NOTCH1 correlated negatively with NOTCH2 and 3 , and CCND1 in smoker donor cells (Supplemental Fig.  4 ). In comparison, with a strong positive correlation between EPCAM , ITGA6 and KRAS observed in both cancer case-donor groups, NOTCH2 and 3 , were positively associated with MYC expression, and further correlated with CCND1 in LUAD, with the association between Notch signaling and ITGA6 and CCND1 lost in LUSC donor cells ( n  ≥ 9; P  < 0.05; Supplemental Fig.  4 ). These results indicate distinctive Notch pathway activity among the cell groups, emphasized by an intense positive correlation with epithelial and proto-oncogenes in LUAD-donor BCs.

Epithelial and Notch pathway-related gene expressional changes with smoking dose and smoking status. Scatterplot depicting relative patient transcript levels by smoking pack years and where indicated grouped by smoking status (Ct normalized to GAPDH ; negative value). (A) Pooling all groups, only the stem cell protein NKX2-1 demonstrated a decline in BC expression with smoking pack years. Among never and ever smokers, KRT14 transcript levels are higher and SCGB1A1 , and CD274 are lower in smokers as compared to that of never smokers. KRT14 levels significantly increase in current smokers with smoking dose. (B) NOTCH2 and HEY1 expression is lower in ever smokers, while NOTCH1 and HES1 levels are specifically reduced in current smokers. Color-coded regression lines ± SEM (shaded) and boxplots representing each group are shown ( n  ≥ 5; * P  < 0.05 and ** P  < 0.01). Results from passage 3 never-smoker (Never), smoker, lung adenocarcinoma (LUAD), and lung squamous cell carcinoma (LUSC) cells are shown

In this study we set out to identify plausible changes of early lung carcinogenesis by examining BCs of smokers, and those with extant but anatomically remote tumors. We further correlated differences with patient age and smoking pack years. Our findings are consistent with reported molecular and functional changes in BCs from smokers [ 3 , 32 , 33 ], and expand on these changes with age- and smoking pack-years and in smoking-related cancers. We also identify Notch signaling trends that presumably precede retarded BC growth in smokers, dysplasia in LUSC, and hyperproliferation in LUAD donor cells. These findings may help reveal distinct biological processes active in early smoking-related NSCLC carcinogenesis, perhaps allowing future risk assessment, earlier cancer identification, and targeted engagement of preventive therapies.

Distinguished by EpCAM cell surface marker expression, our results indicate that the cultured BC population exists in a transitional epithelial/mesenchymal state, with the fraction of ITGA6 and clonogenic EpCAM /ITGA6 /CD24 expressing cells (which increase in never smokers with donor-age and smoking pack-years) largely reduced in smoking donors. We posit that smoking impairs BC proliferation and differentiation and disrupts populational steady-state further supported by a decrease in NOTCH1 , HES1 , and SCGB1A1 transcript levels, the latter previously reported in smoker BCs [ 33 ]. Correlated with airway epithelial injury and metaplasia [ 34 ], we also identified a smoking-specific populational elevation of KRT14 expression in BCs (cancer cases included) to imply the use of this transcript as a potential biomarker of smoking-related damage and cancer.

Observed to undergo changes in our study, EpCAM (epithelial) and VIM (mesenchymal) protein expression levels and cellular localization patterns were previously shown to serve as important cancer prognostic markers. EpCAM to induce target genes that include CCND1 and the MYC proto-oncogene, and VIM to destabilize Notch-mediated pathway signaling [ 35 , 36 , 37 ]. Indeed, defective Notch signaling coupled with a large dysplastic spindled subset in LUSC donor BCs may indicate acquisition of neoplastic properties as spindled cells have been shown to be linked to cancer cell stemness and pleomorphy seen in lung carcinomas in situ [ 38 , 39 ]. Thus, our findings may elucidate early molecular patterns that confer cancer-related growth properties upon smoker lung epithelial progenitors.

Also strongly associated with tobacco smoke exposure, LUAD donor BCs were shown to exhibit robust cellular hyperproliferation, with lines of evidence pointing toward a defect in G1/S checkpoint regulation, premature entry into the S-phase, and an average increase in nuclear size, a phenomenon reported during the transition of benign breast disease cells to carcinoma [ 27 ]. As LUAD is considered to arise in the distal lung, the reason for these findings in cells procured from the proximal lung remain obscure but may be explained by confounding observations that include aberrant BC transition and/or Notch programming changes, shown to occur as early as the atypical adenomatous hyperplasia stage of LUAD carcinogenesis [ 34 , 40 ]. While others indicate NOTCH1 to be active in smoker BCs and carcinogenesis [ 2 , 41 ], we identify an association between Notch with its mediator, MYC and KRAS proto-oncogenes, and CCND1 , a key regulator of S-phase entry (and second most frequently amplified gene in solid cancers). In fact, KRT14 and SCGB1A1 expressional defects, reported in adenosquamous cancer progenitor cells, can also be directly related to Notch signaling [ 37 , 42 , 43 ]. Taken together, atypical Notch and cancer gene expression, select lineage anomalies, and growth abnormalities support our hypothesis that “cancer field” BCs exhibit pre-cancer or cancer-related properties. This assumption and the precise signals and sequence of events that can promote BC oncogenic transformation warrant future studies.

These findings should be interpreted in the context of the study design which selects for cytologically normal bronchiolar BCs in smoking and cancer patients and compares them to never-smoking controls. One limitation obligate in human invasive studies such as this one is the cross-sectional, single timepoint model of events that, in actuality, unfold over time. Another is the small sample size, coupled to clinically relevant covariates inherent in such a study (age, smoking, cancer subtype, etc.) that unfortunately did not permit staunch multivariate analyses. As for bias, the average age of the control group was lower than case individuals, and the smoking dose (pack years) was found to be significantly higher in cancer cases, introducing possible age- and a smoking dose-related bias. Similarly, within the studied cancer groups, patient cancer stages from IA-IV were pooled, perhaps weakening our findings of cancer stem cell development.

Because BC cultures have been shown to accumulate mutations and select for an activated state of injured or airway repairing cell derivatives [ 44 ], we worked to minimize driver gene somatic mutations and clonal selection in vitro by performing experiments on low passage cells in short term cultures, which our group had previously demonstrated to reduce confounding factors in the single cell [ 17 ]. Moreover, as BCs were procured remote from any tumor, cytologically classified as non-malignant, and detected in non-cancer groups, these cells do not plausibly represent tumor or tumor-disseminating cell lineages. Next, while we refer to the EpCAM neg BC subset as a product of EMT, we cannot rule out that this population is a result of changes in protein stability/folding associated with cultivation or cell dissociation methods used. Alternatively, these cells may represent a contaminating population of stromal or hematopietic lineage, previously shown by our laboratory to accompany lung stem cells in primary culture [ 45 ]. While in such a case our results would not directly reflect on BC traits, these findings could help illuminate properties of the immediate (stem cell) niche. Finally, it is possible that the EpCAM neg fraction of the BC population represents a previously reported dormant stem cell population, protected from smoking-triggered mutations, that upon smoking cessation can revert to (and outcompete mutated) epithelial BCs to repair the lung [ 2 ]. Future studies focusing and expanding on selective pressures, immunophenotype, and malignant potential, which include a viable equilibrium between EpCAM pos and EpCAM neg lineages, changes in nerve growth factor receptor pathway activity, and BC clonogenicity and invasion are warranted to facilitate our understanding of smoking-related lung injury and “low mutational” progenitor cell carcinogenesis.

In summary, our findings uncover smoking-, age-, and cancer-related phenotypic and molecular footprints of broad field BCs, some of which may be driven by early changes in Notch signaling. Understanding transitional developments in smoker BCs can potentially be leveraged into strategies leading to earlier lung cancer detection and the development of prevention therapies.

Data availability

No datasets were generated or analysed during the current study.

Abbreviations

• Basal cells

Epithelial-mesenchymal transition

Lung adenocarcinoma

Lung squamous cell carcinoma

• Non-small cell lung cancer

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Acknowledgements

This research was supported in part, by 1R21CA209436-01A1 (MPI Spivack/Vijg); U01HL145560 (Vijg, Spivack contact); 1 U01 ES029519-01 (Spivack, Vijg contact), Presidential Research Development Touro University, and Stony-Wold Herbert Foundation (YP). We would like to thank Zvi Goldman and Yaakov Kalikstein for data collection and Drs. Jinghang Zhang and Lydia Tesfa from the Einstein Flow Cytometry Core Facility for technical support.

1R21CA209436-01A1 (MPI Spivack/Vijg); U01HL145560 (Vijg, Spivack contact); 1 U01 ES029519-01 (Spivack, Vijg contact); Presidential Research Development Touro University and Stony-Wold Herbert Foundation (YP).

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Simon Spivack and Yakov Peter are Co-senior authors.

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Department of Biology, Lander College, Touro University, New York, NY, 11367, USA

Olsida Zefi, Spencer Waldman, Yosef Sonbolian & Yakov Peter

Biology and Anatomy, New York Medical College, 10595, Valhalla, NY, USA

Pulmonary Medicine, Albert Einstein College of Medicine, Bronx, NY, 10461, USA

Spencer Waldman, Ava Marsh, Miao Kevin Shi, Batbayar Khulan, Taha Siddiqui, Aditi Desai, Dhruv Patel, Aham Okorozo, Samer Khader, Jay Dobkin, Ali Sadoughi, Chirag Shah, Simon Spivack & Yakov Peter

Lander College Touro University, 75-31 150th Street, 11367, Kew Garden Hills, NY, USA

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OZ, KB, SW, AM, MKS, YS, BK - contributed to the acquisition, analysis, or interpretation of data for the work. TS, AD, DP, AO – Subject recruitment. JD, AS, CS – bronchoscopist. SK - cytopathologist. SDS and YP conception and design of the work and final approval of the version submitted for publication.

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Supplementary Material 1

: Supplemental table 1: PCR primers used in this study.

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: Supplemental Fig. 1. Molecular expression and morphology of BC lineages. (A) Tumor protein 63 ( TP63 ), cytokeratin 14 ( KRT14 ), and cytokeratin 5 ( KRT5 ) lineage marker mRNA transcript expression in cells of the four groups: never-smoker and smoker controls, and lung adenocarcinoma and squamous cell carcinoma (LUSC) donor cases as determined by qRT-PCR. Box plots represent median and quartiles of individual gene cycle threshold (Ct) relative to that of GAPDH (at a negative value). Differences in relative KRT14 transcript levels between the groups are statistically significant ( n  ≥ 7; * P  < 0.05 by ANOVA). (B) Immunoblots depicting protein expression in the cell populations. Cells were harvested, cultured, and 30 µg of protein was loaded. An ACTB loading control is also shown. (C) Immunofluorescence micrographs demonstrating BC lineage protein expression in the four groups. From left to right; DAPI nuclear counterstain (blue); TP63 (green); KRT14 (red); and merge. (D) No differences in the expression of the BC lineage markers podoplanin ( PDPN ) and the nerve factor growth factor receptor ( NGFR ) were observed among the groups ( n  ≥ 2). Passage 3, cells from never-smoker (Never), smoker, lung adenocarcinoma (LUAD), and squamous cell carcinoma (LUSC) patients were used in this set of experiments. Supplemental Fig. 2. Triple positive cells in cancer cases and control. Box and whisker plots depicting a decreased but non-significant difference in the fraction of passage 3 triple positive (EpCAM pos /ITGA6 pos /CD24 pos ) cells procured from cancer cases (LUAD + LUSC) versus controls (never smokers and smokers). n  ≥ 9; non-significant. Supplemental Fig. 3. LUAD patient BCs exhibit significantly larger nuclei. Passage 3 cells were labeled with DAPI, photographed under identical settings, and three equivalent fields from each patient were taken for morphometry. (A) Box and whiskers plot depicting median and quartile of never-smoker (Never), smoker, lung adenocarcinoma (LUAD), and squamous cell carcinoma (LUSC) nuclear sizes (left) and intensities (right). Cells grown from LUAD biopsies displayed significantly larger nuclear sizes ( n  ≥ 4; * P  < 0.05 by ANOVA). RU – relative units. (B) Representative DAPI images (Top) and nuclear outlines (bottom) are shown. Supplemental Fig. 4. Pairwise association between select notch, epithelial, and proliferative genes within the groups. Heat maps depicting correlation between normalized mRNA transcript gene expression from: (A) Pooled groups, (B) never-smokers, (C) smokers, (D) lung adenocarcinoma, and (E) lung squamous cell carcinoma donor cells (Passage 3). Note differing relationships between cellular gene expression (Passage 3) among the patient groups ( n  ≤ 7; * P  < 0.05; ** P  < 0.01; and *** P  < 0.001 by Pearson’s r).

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Zefi, O., Waldman, S., Marsh, A. et al. Distinctive field effects of smoking and lung cancer case-control status on bronchial basal cell growth and signaling. Respir Res 25 , 317 (2024). https://doi.org/10.1186/s12931-024-02924-w

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DOI : https://doi.org/10.1186/s12931-024-02924-w

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