Population GrowthA major question is the effect of the growing population on the environment. The search for answers to this question has become increasingly(1) complex and controversial(2). In general, ecologists and biologists tend(3) to be pessimistic about the damage growing populations cause to the environment, based on their assumption(4) that ecosystems have a limited “carrying capacity”(5), or ability to support life. Eventually, they say, the environment will no longer be able to renew itself and will collapse (6). Economists, on the other hand, are often optimistics; they trust the free market and human ingenuity(7) to develop new technology for coping with(8) ever-larger numbers and scarce resources. “But no science so far has been able to actually quantify the role of population on the environment,” says Robert Engelman, director of the Population and Environment Program at Population Action International in Washington, DC. “at this point, there’s no direct way to prove that, say, 80 million more people in a region had a particular impact on the water or air quality. However, it is clear that population is often the critical variable that can cause the degradation and even collapse of natural systems.” As population grows, so will the pressure new generations exert on natural resources. The list of environmental problems aggravated(9) by growing populations includes deforestation and desertification, loss of top soil, poisoning of drinking water and pollution of oceans, shrinking wetlands, shortage of fuels such as firewood, exhaustion of oil reserves and of various mineral resources, siltation in rivers and estuaries(10), dropping water tables, erosion of the ozone layer, loss of species and wilderness areas, global warming, rising sea levels, nuclear waste, air pollution, and acid rain. Any population increase often means putting more land under cultivation and raising the production per acre(11), steps that can require more capital, fertilizers, pesticides, and water irrigation. In the United States Almost all arable land is now under production, leading to soil erosion. Water consumption naturally rises with population growth, and the country’s huge groundwater aquifers are disappearing. Parts of Texas and Arizona have already been pumped dry and can no longer be farmed. In addition, rapidly growing populations in Mexico, the Philippines, Indonesia, Brazil have caused environmentally fragile lands to be overfarmed and depleted. The loss of natural habitats to more and more cropland reduces the biological diversity(12) of plants and animals. Water tables are quickly dropping in the developing world, especially in the Middle East and Africa. The numbers of people there have risen beyond the water’s ability to renew itself. And in Zambia, for example, population size has generally exceeded the forest’s ability to regenerate. So the forest has stopped, and is now moving back. In addition, While the world population was doubling between the 1950s and 1980, its commercial energy consumption increased threefold. As a result of the higher demand, energy suppliers are mining more coal and building more dams and hydroelectric and nuclear power plants. The increases activity has led to higher levels of polluting emissions and waste. Levels of carbon dioxide and methane in the atmosphere are also tied(13) to a region’s population size. With more than 20 million people, Mexico City has the largest population of any city in the world, and the worst air pollution. Demographers predict its population will grow to more than 30 million people. In the United States alone, ever-increasing car driving and industrial activities now pump an estimated 23 million tons of sulfur dioxide into the atmosphere. The acid rain this chemical helps create then damages aquatic and forest life, often thousands of miles away from the source. However, some experts argue that environmental problems are not a sole result of population size.
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