Making the Link: Population, Health, Environment

Also available in PDF (PDF: 234KB)

by Jonathan G. Nash and Roger-Mark De Souza

(July 2002) The number of people on Earth, where they live, and how they live all affect the condition of the environment. People can alter the environment through their use of natural resources and the production of wastes. Changes in environmental conditions, in turn, can affect human health and well-being. Human demographic dynamics, such as the size, growth, distribution, age composition, and migration of populations, are among the many factors that can lead to environmental change. Consumption patterns, development choices, wealth and land distribution, government policies, and technology can mediate or exacerbate the effects of demographics on the environment. The precise impact of a given change depends on the interplay among all these factors, but it is clear that demographic change can affect the environment.

This report provides information and data on critical linkages between human beings and the environment. The Population Reference Bureau's Population, Health, and Environment (PHE) Program promotes a better understanding of such linkages by examining their causes, their consequences, and how they can be addressed. For more information on the program, please write to us at [email protected].

Urbanization has both positive and negative effects on the environment

Almost 3 billion people worldwide live in urban areas, with more people joining them every day. People may choose to move because of a variety of "pull" and "push" factors: They may move to urban areas to take advantage of economic opportunities offered in cities, or because of degraded environments in rural areas. Human pressure on natural habitats in rural areas is often reduced as people move from rural areas to cities. Urbanization can improve living standards, since urban residents tend to have higher incomes, longer life expectancy, and improved access to services. Population growth may slow, because urban women tend to have fewer children than rural women. But cities also produce concentrated amounts of solid waste, sewage, and air pollution, as well as demands for energy, food, and other resources. In many rapidly growing cities, supplies of clean water, electricity, housing, roads, and sewage treatment facilities cannot keep up with population increases. Such rapid growth can hinder the development of adequate infrastructure and regulatory mechanisms for coping with these side effects of growth, contributing to negative health consequences.

Demands on natural resources will continue to grow as young people establish their families

One-third of the world's population in less developed countries is under age 15

Source: United Nations, The Sex and Age Distribution of the World Populations: The 2000 Revision (medium scenario).

There will be continued population growth and demand on natural resources as the over 2 billion young people in the world become the world's newest set of parents.

There have never been so many people below age 20, particularly in less developed regions. As these young people leave their parents' homes in search of new opportunities, set up their households, and begin having children, levels of migration, urbanization, consumption, and population growth are likely to increase.

Population, economic, and political factors affect consumption levels and environmental impact

The world's richest countries, home to 20 percent of the world's population, account for 86 percent of total private consumption. The poorest 20 percent of the world's people account for less than 2 percent of private consumption. Environmental degradation in less developed countries is more often the result of poor people struggling to acquire basic essentials, such as food, water, shelter, and fuel. In more developed countries, environmental stress, such as pollution, is usually caused by high consumption levels and greater industrial activity. In highly developed countries, however, certain environmental pressures may subside as production efficiencies and the ability to enforce environmental regulations improve. Environmental pressures may also change due to structural shifts, such as a move from an industrial economy to a service-based economy or as pollution-causing factories are moved to other countries.

Increasing numbers of people and more energy-intensive economic activity could increase carbon dioxide emissions

Rising affluence, increasing population, and continued reliance on fossil fuels may result in increased levels of greenhouse gases, including carbon dioxide, that have been implicated in global warming. Global warming can have serious impacts; for example, as the polar caps melt, rising sea levels could threaten human populations in low-lying coastal areas. Shifting climate patterns may also accelerate the extinction of plants and animals, and spread tropical diseases, such as malaria. Recent developments in alternative energy sources, pollution-control technologies, fuel-cell technology, and international agreements may hold promise for reducing future carbon dioxide emissions.

Land-use change often creates threats to human and ecological health

Meeting the needs of a growing population frequently requires some form of land-use change, such as clearing forest land in order to expand food production. These changes often have environmental repercussions; deforestation, for example, can exacerbate the frequency and severity of floods, and contributes to species decline due to habitat loss. Deteriorating environmental conditions associated with expanding agriculture or deforestation can pose threats to human health. For example, deteriorating water quality can contribute to the spread of communicable diseases. Similarly, reliance on chemical fertilizers to improve agricultural production can degrade soil, and improper handling of such compounds can cause cancer and other health problems in humans.

Declining availability of fresh water threatens human well-being and environmental quality

Water is vital for all living organisms and ecosystems, and it sustains humans' health, food production, and industrial activities. Water helps maintain a balance in Earth's systems by providing nutrients for plants and animals and by cooling and cleansing the environment. Freshwater availability can become an issue when water is scarce or when population increases outpace the available water resources. Countries are considered "water scarce" when their renewable water resources drop to below 1,000 cubic meters per person per year; anything below this level is a severe constraint on human nutritional requirements. Ultimately, water shortages pose a threat to human health and environmental quality.

Jonathan G. Nash is a policy analyst at PRB.

Roger-Mark De Souza is technical director of the Population, Health, and Environment program at PRB.

This article is excerpted from a wallchart that shows environmental and population data for 123 countries. It's available from PRB's Online Store or as a booklet: (PDF: 234KB).