Annual Renewable Freshwater Availability per Capita, 1950, 1995, 2050

Source: Population Action International, Sustaining Water, Erasing Scarcity.

Teachers Guide: Discussion questions

Question & Answer: Does the relationship between population change and the environment vary by region?

Population growth and distribution have significant roles to play in the sustainability of the world's vast resources. Not only the number of people, but also the lifestyle, consumption patterns, and regions people inhabit and use directly affect the environment. The relationship between population growth and environmental degradation may appear to be rather straightforward. More people demand more resources and generate more waste. Clearly one of the challenges of a growing population is that the mere presence of so many people sharing a limited number of resources strains the environment. But when looking at the impact of human activities, the situation is more complicated due to the wide variety of government policies, technologies, and consumption patterns worldwide.

The link between population growth and the environment is found somewhere between the view that population growth is solely responsible for all environmental ills and the view that more people means the development of new technologies to overcome any environmental problems. Most environmentalists agree that population growth is only one of several interacting factors that place pressure on the environment. High levels of consumption and industrialization, inequality in wealth and land distribution, inappropriate government policies, poverty, and inefficient technologies all contribute to environmental decline. In fact, population may not be a root cause in environmental decline, but rather just one factor among many that exacerbate or multiply the negative effects of other social, economic, and political factors.

Many of the world's population live in poor countries already strained by food insecurity; inadequate sanitation, water supplies and housing; and an inability to meet the basic needs of the current population. These same countries are also among the fastest growing places in the world. A large proportion of these populations are supported through subsistence agriculture. As populations grow, competition for fertile land and the use of limited resources increase. The people living in these countries are also moving toward a greater standard of living, perhaps matching the lifestyles of the more developed countries whose current consumption patterns and resource use are not necessarily sustainable.

Food Production

Meeting the increasing demand for food is probably the most basic challenge and the most salient population and environmental crisis. But the fear that population size would one day exceed the food supply has not proved true. With the development of fertilizers, pesticides, and more efficient farming techniques, crop yields per acre have increased and the amount of land under cultivation has expanded. World food production has kept pace with population growth. Yet ironically, millions of people do not have enough to eat. Food insecurity is often a result of the unavailability of food, insufficient purchasing power, inappropriate distribution, or inadequate use of food at the household level. Poverty, natural disasters, political violence, and other geopolitical factors create a disproportionate distribution of the world's food.

The gains in food production have been a result of increased yields in fertile lands and new cultivation of marginal lands through industrial agriculture. However, improper use of machinery, chemicals, and extensive irrigation, has resulted in the degradation of land and water resources. Land is made vulnerable to wind and water erosion. Misguided irrigation practices can mean an increase in soil salinity and a greater demand on irreplaceable groundwater. Chemical runoff from fertilizers and pesticides also damage water resources.

Nonindustrial farming or traditional agriculture that continues to intensify in less developed countries often involves the cultivation of fragile soils that are difficult to farm, such as drylands, highlands, and forests. When farmland expands toward fragile lands in order to keep pace with the needs of a growing population in a region, it can lead to deforestation, erosion, and desertification.

Water Resource Management

Population growth and distribution have always been linked to the availability of freshwater and the sustainability of renewable water resources. The demand for water has grown significantly over the last 50 years not only because of population growth, but also because of an increase in the uses of water for households, agriculture, and industrial production. Appropriate management of the world's water resources is essential for meeting the demands of a growing population and for expanding water uses. At the same time, we must also prevent the further degradation of our water sources and clean up polluted waters.

A significant number of the world's population lack access to an adequate supply of safe water for household use. In certain less developed countries, more than one-half of the population is without access to safe water. Water shortages and polluted waters lead to food insecurity and major health problems among the world's poor.

Because water does not stop at national boundaries, the use of water upstream, pollution, and reduced flows will affect countries downstream. The future of the world's water resources depends on improving management policies and practices globally. Water management institutions must incorporate efficient techniques for using water in industry and agriculture. And most important, management policies must involve the interests of the local community in collaboration with national governments in order to protect water rights and ensure success of programs.


CO2 Emissions per Capita, 2002

  Metric tons
Less Developed 2.1
More Developed 11.7
Africa 1.1
America--Latin America/Caribbean 2.5
America--North 19.6
Asia 2.6
Europe 8.4
Oceania 12.2

Source: Carl Haub, 2007 World Population Data Sheet.

Carbon dioxide emissions have grown dramatically in the past century because of human activity, chiefly the use of fossil fuels such as oil and coal, as well as changes in land use such as cutting down forests. These emissions are a key contributor to climate change that is expected to produce rising temperatures, lead to more extreme weather patterns, facilitate the spread of infectious diseases, and put more stress on the environment. The United States is the largest contributor of total carbon dioxide emissions, and has one of the highest per capita rates. The U.S. per capita emission rate has risen from 19.2 metric tons per person to 19.9 metric tons between 1990 and 2002, according to the World Resources Institute. Per capita use also has gone up in China, rising from 2.2 to 2.9 metric tons between 1990 and 2002. China is expected to surpass the United States in total carbon dioxide emissions by 2009.

The vast majority of energy comes from the burning of fossil fuels (oil, natural gas, and coal). The increased use of fossil fuels has a negative effect on the health of the environment in terms of air and water pollution. Air pollution from greater coal use and vehicle exhaust has led to acid rain, which is particularly damaging to forests, lakes, and streams. Rising fossil fuel use also means a greater build-up of carbon dioxide in the atmosphere, higher greenhouse gas emissions, and global warming.

The environmental costs of using fossil fuels have led to efforts to decrease their level of use. Alternative energy sources that are more efficient are being sought, such as renewable resources like hydropower and solar power. Reducing the environmental costs from energy consumption and ensuring there will be an adequate supply of energy for the future involves the careful management of existing and potential resources.


Deforestation: The loss of trees due to overcutting of forests. One consequence of deforestation is soil erosion, which results in the loss of protective soil cover and the water-holding capacity of the soil.

Desertification: The process of grasslands being converted to desert mainly as a result of deforestation, overgrazing, and erosion due to poor land management.

Food insecurity: A situation that exists when people lack secure access to sufficient amounts of safe and nutritious food for normal growth and development and an active and healthy life. Food insecurity may be chronic, seasonal, or transitory.

Fossil fuel: A group of primary energy sources created from the incomplete biological decomposition of dead organic matter. The fossil fuels include oil, coal, and natural gas and account for about 90 percent of all the energy consumed in the world.

Irrigation: The practice of supplying land with water artificially by means of ditches, pipes, or streams.

Less developed countries: Less developed countries include all countries in Africa, Asia (excluding Japan), and Latin America and the Caribbean, and the regions of Melanesia, Micronesia, and Polynesia.

More developed countries: More developed countries include all countries in Europe, North America, Australia, New Zealand, and Japan.

Renewable water: The surface water runoff from local precipitation, the inflow from other regions, and the groundwater recharge that replenishes aquifers.

Subsistence agriculture: Farming at a level at which only enough food is produced to meet immediate local needs.