The conventional wisdom since the 1970s has been that the most severe long-term problem for the environment is overpopulation. Overpopulation leads to food shortages, farming of marginal lands and depletion of soil, clearing of tropical forests for agriculture, etc. In this view, the problem resides in nations whose birth rate, even if declining, is still very high. One author recently conveyed the alarming disparity in birth rates: in three generations, a German woman would have 6 descendants, in the U.S., 14, and in Africa, 258. The implication, of course, was that by the middle of the next century, Africans would be depleting resources 18 times more quickly and damaging the environment 18 times more severely than people in industrialized nations.
Not all humans consume resources at the same rate, however. Nor do all products affect the environment to the same degree. Paul Ehrlich has summarized environmental impact in the simple equation:
I = PATImpact is a function of Population times Affluence (per capita consumption) times the level of Tech-nology used to produce goods (energy, waste). In this view, per capita consumption and technology are as significant as the number of people. The figures on the opposite page (formatted for an overhead or handout) thus offer an interesting counterpoint to figures on population.
Who most affects the environment? According to one estimate, a person in the U.S. has 50 times more adverse impact than someone in Bangladesh. An American, on the average, consumes 50 times as much steel and 300 times as much plastic as someone in India. When one examines consumption rather than just population, the environmental problem of scarcity looks very different.
One way to gauge consumption or impact on the environment is through the familiar camper's back-country ethic, "leave a campsite as you found it." In other words, if you leave an environment in worse condition than when you arrived, or if you consume more than you produce so that less remains, then someone else must bear the consequences of your acts. Others bear the burden of your environmental degradation and/or depletion. The general ethical principle is that a person should take responsibility for his or her own actions, respect others and not impose costs on them. This leads to an ethic of maintaining an ecologically sustainable lifestyle.