Population growth and environmental impact

• DEFINITION: Increase in the numbers of human beings inhabiting the earth

Population growth challenges the world’s economy, social structures, and environment. The precise value of the theoretical maximum population capacity of the planet depends on the availability of natural resources, the acceptable quality of life, the role of technology, and the values underlying the human relationship with nature.

Although numbers vary by source, by January 2023, the earth was estimated to have surpassed the 8 billion person mark. The United Nations estimated that the world population would continue to grow over the subsequent half-century, reaching a peak of 10.3 billion people by the mid-2080s. This population explosion is unprecedented in human history. The estimated population of the world in 8000 BCE was about 5 million. It did not reach 500 million until around 1650, but then the rate of increase accelerated. By the mid-nineteenth century, the planet held 1 billion people; by 1975, the number was 4 billion.

Even though the fertility rate—the average number of children born per woman—declined after the late 1960s, vigorous growth is expected to continue through the twenty-first century, and perhaps beyond. Whatever the actual world population total throughout the twenty-first century, the distribution of the population will change as people migrate to urban areas, with the world’s population shifting so that, for the first time in history, more people live in cities than in rural areas. Most of the total population growth and urban growth will occur in developing countries, particularly those in Africa.

How much population increase can the earth’s environment sustain? Answers to that question are often biased by ideology, religious tenets, and interpretive methods, so that estimates vary by nearly four orders of magnitude: from 500 million to 1 trillion. Most, however, fall between 6 and 10 billion, which would mean that the planet’s carrying capacity has been exceeded or will be exceeded within one century. The degradation of the global environment—or at least the locales of the greatest population concentrations, the sea coasts—could endanger billions of people and far greater numbers of wildlife.

Resources

Humans affect the allocation of natural resources by displacing or consuming them. Many resources are renewable, such as forests, which can be regrown. Nevertheless, scientists fear that increased demands for such raw materials may surpass the rate of replacement. For example, increasing use of wood could cause loggers to cut down forests faster than new trees can grow; eventually, the amount of wood available would diminish. Moreover, spreading urban areas and agriculture could take over land that once supported forests.

Some resources are gone forever once used, leaving none for future consumers and necessitating replacement by other materials if the enterprises dependent on the originals are to continue. For example, if petroleum reserves are depleted, propane or natural gas might serve as replacements for heating and vehicle fuel. Not all such nonrenewable resources are replaceable, however. The biodiversity of nature is the critical example, although some commentators insist that biodiversity is not a resource for exploitation but a heritage that should be safeguarded. In any case, proponents of the preservation of biodiversity believe that the destruction of natural habitats and the attendant extinction of species obliterate much-needed new sources of food and medicines.

Species die out naturally. All the species now living on earth amount to only 2 to 4 percent of those that ever existed. Nonetheless, biologists believe that because of human expansion, pollution, and increasing energy consumption, a mass extinction is under way that is as serious as the one that killed the dinosaurs during the Jurassic period. The current extinction rate is calculated to be ten thousand times higher than the average rate before the rise of humans. Of the five to ten million species thought to exist, ten thousand to twenty-five thousand disappear every year. Most are unrecorded insect species, but since 1650 about 1 percent of recorded bird and mammal species have become extinct, and about 20 percent are threatened with extinction.

People also change the character of the land and its fresh water. Land cleared for wood or farming is subject to erosion, and soil fertility declines with heavy agricultural use, especially because of monoculture crops, overgrazing, and some irrigation methods. According to the United Nations, every year about 12 million hectares of arable land dry up because of human enterprise, representing a space where 20 million tons of grain could have been grown. Innovations in agricultural methods, known as the Green Revolution, multiplied crop yields and more than made up for the loss in arable land during the late twentieth century, but accelerating growth and desertification are expected to strain farmers’ ability to feed the population.

Little can be done about the diminishing supply of fresh water except conservation and antipollution measures. Some 780 million people live without access to safe water, according to the World Health Organization in 2012; by 2025, the number is projected to more than double. Polluted water threatens health and agriculture, especially in developing countries, where populations are increasing the fastest. Political scientists worry that competition among nations for declining water resources could escalate into armed conflict in Africa, Central Asia, the Middle East, and South America.

Correlations between population and size and pollution are apparent. For example, according to the National Air and Space Administration, larger concentrations of air pollution are more prevalent in urban areas. Air pollution also increases with expanding industry and transportation. Changes in atmospheric chemistry from particulates, hydrocarbons, carbon monoxide, nitrogen oxides, and sulfur oxides cause acid rain and smog in urban regions; some pollutants also trap solar energy, creating a greenhouse effect, or destroy ozone high in the atmosphere. The increase in average temperatures and ultraviolet radiation because of these effects will further threaten crops, human health, and wild flora and fauna.

Politics and Economics

Proposals for dealing with population growth tend to emphasize either restricted fertility or economic development, and sometimes both. Nationalism and international politics, however, complicate the establishment of policies and make implementation difficult.

Attempts to restrict fertility take various forms. A government may specify by law the number of children each couple may have. The People’s Republic of China is the best-known example of this approach: Its one-child policy, introduced in 1978, was intended to control the world’s largest national population—more than 1.37 billion in 2017. Although recognizing that China desperately needs to check growth, humanitarian groups denounced the Chinese government for violating human rights in carrying out the policy. Most observers doubt that such a restrictive population-control policy could be effective in a country without a dominating central government like China’s. The policy began to be phased out in 2013, and officially ended in 2016, when a law went into effect increasing the number of children allowed to two. After census statistics showed China's birth rate was continuing to decline, the government raised the number of children to three in 2021.

Nevertheless, by 2023, China reported its first population decrease in over six decades. The Chinese population showed a decrease of 850,000 persons from the previous year. Although China’s population remained at 1.41 billion people, an important implication of this data is that China may not be able to sustain its economic growth rate from previous decades. In addition, the Chinese population is aging. Future generations of Chinese may have to contend with smaller younger generations supporting older generations, who are much greater in number.

Other nations and international organizations encourage limiting family size through two other methods. One is to teach women family-planning techniques and offer them contraceptive devices or drugs. The other is to raise the educational level of women in general to encourage women to enter the workforce. Studies in all countries show that educated, working women have fewer children on average than do uneducated women who stay at home. However, great obstacles confront such efforts. Some religions prohibit or discourage the use of contraceptives. Also, the governments of developing nations are frequently suspicious of family-planning programs financed by rich countries or the United Nations, afraid that the programs are really covert political sabotage. Most often, however, cultural traditions forbid women to compete with men intellectually or economically.

Meanwhile, in the United States, the population continued to grow. On January 1, 2023, the United States Census Bureau placed the nation’s population at 334,233,854 or about a half percent higher than the same day in 2022. The US Census Bureau predicted that such growth would peak by 2080, when the US population was estimated to be near 370 million.

Proponents of economic development argue that resources can be further developed and more efficiently used to accommodate population growth, but criticism also plagues their efforts. Conservationists throughout the world, especially in industrialized regions such as North America and Europe, are the leading opponents, especially if the development entails exploitation of nonrenewable resources, anticipation of new technologies, or increased pollution. The governments of developing nations join in denouncing the economies of developed countries, accusing them of overconsumption and unwillingness to control their own pollution. Wealthy nations account for only one-sixth of the world’s population but control three-fourths of the world’s gross product and trade. Moreover, industrialized nations pollute far more than do developing nations; the United States alone, with only 5 percent of the world’s population, produces 20 percent of the carbon emissions that contribute to global warming.

Some political theorists assert that the effects of population growth may be mitigated by more equitable distribution of wealth and political power. They argue that less wasteful consumption will decrease pollution and husband resources, while freer trade and better distribution of land and the capital to develop it wisely will end such harmful practices as slash-and-burn agriculture. Stronger international institutions, many propose, could administer the needed economic and political changes. The twentieth century saw the globalization of markets, encouraged by such treaties as the General Agreement on Tariffs and Trade (GATT), which may, over time, help equalize use of labor and resources. However, resistance from national governments to new worldwide political institutions and economic systems is daunting.

Philosophical Issues

Deep philosophical differences also trouble the debate on population growth. The Roman Catholic Church, for instance, treats the environment and population matters as separate issues and teaches that contraception is immoral because it is contrary to the family’s purpose to procreate. The Church vigorously objects to government interference in family life and permits birth control by rhythm method (sexual abstinence during ovulation) alone. Some radical environmentalists, by contrast, want to halt human reproduction altogether until the population returns to pre-Industrial Revolution levels or lower.

These antithetical positions reflect two fundamental questions. First, is humanity to be considered part of nature? Much Western philosophy and theology holds humanity to be superior to nature according to divine law or distinct from it because humans alone possess intelligence. On the other hand, many non-Western thinkers and environmentalists consider humanity to be an integral part of nature, or the “web of life”—in this view, species are mutually dependent on each other, and none is superior. Second, should humans take from the environment whatever they want when they want it, or should they consume only in such a way that biodiversity is not threatened?

Even if all of humankind were to agree on answers to these questions, the environment itself might settle the problem of population growth. Some scientists fear that the global environment is so intricate, complex, and fragile that if it is stressed too much, a “jump effect” could occur in which the earth’s ability to support humans and other large organisms would decline precipitously—faster than human technology or conservation could compensate.

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