As the 21st century begins, growing numbers of people and rising levels of consumption per capita are depleting natural resources and degrading the environment. In many places chronic water shortages, loss of arable land, destruction of natural habitats, and widespread pollution undermine public health and threaten economic and social progress (21, 30, 202). Many experts think that current trends cannot continue much longer without dire consequences (57, 122-124, 128, 158, 202, 249).

In most developed countries population is growing slowly or no longer growing at all, but levels of per capita consumption are so high that the environment is under pressure. Most developing countries face even greater pressures, however. Population is growing rapidly, while consumption is increasing as living standards improve. Every person has an equal right to achieve a high standard of living. But, if every person in the world consumed as much as the average American or Western European, the demand for natural resources would exceed nature's supply (222).

"There is no question that improving standards of living for the current poor of the world, plus providing for the billions still to come, will increase global demand for food, water, energy, wood, housing, sanitation, and disposal of wastes," writes Richard E. Benedick, former US assistant secretary of state responsible for population and environmental policies (11). One of the world's main challenges is practicing sustainable development—that is, improving living standards today without foreclosing the opportunities of future generations to meet their needs (227, 256, 258, 259, 264).

JHU/CCP Motor vehicles clog the “beltway” around Baltimore. In developed countries high levels of per capita consumption are polluting the air and water and using up natural resources. Developing countries face environmental challenges as they seek to raise living standards in the face of rapid population growth.