ABSTRACT
Current rates of population growth and resource consumption may not be ecologically sustainable for more than a few decades; they are resulting in harm to our air, water, land, and other natural resources and are jeopardizing our future well-being. Recently the rate of environmental decline has greatly accelerated. On average, resource use nearly tripled between 1950 and 1990. This growth, combined with widespread use of harmful technology and a doubling of human population, resulted in roughly a sixfold increase in human impact on the global environment during the four decades. This estimate is based on the formula stating that environmental impact (7) is the product of the number of people (P), resource use per person (R), and environmental degradation from technologies employed in resource use (I): I = PRT. 1 These factors are also central to the concept of global carrying capacity, defined as "the maximum human population that the Earth can support indefinitely on a specific resource base and at a specific level of technology." 2 Human activity is now altering the Earth's basic life-support systems and cycles, including the atmospheric system and carbon, nitrogen, sulfizr, hydrologic, and biologic cycles. 3 Biologists have estimated that humans are appropriating, directly or indirectly, nearly 40 percent of the Earth's terrestrial food resources. 4
