. He mentioned "positive checks" such as war, famine, and disease, and "preventative checks" such as celibacy and contraception (Microsoft Encarta 1998). The world's population will soon reach a level where there will not be enough resources to sustain life, as we know it. During the last half-century, world population has more than doubled, climbing from 2.5 billion in 1950 to 5.9 billion in 1998. There has been more growth in population since 1950 than during the 4 million preceding years since our early ancestors first stood upright (Brown, Gardner, & Halweil, 1999). This unprecedented surge in population, combined with rising individual consumption, is pushing our claims on the planet beyond its natural limits. Many environmental, social, and economic problems either stem from or are increased in magnitude by the overpopulation problem. With an exponentially increasing population, the problems created by overpopulation grow correspondingly. Population growth is out-spacing growth in agricultural production and it is putting increasing pressure on erodible soils, grazing lands, water, and fuel-wood supplies (Chapman, Peterson, & Smith-Moran, 2000). To ensure population stability not only in the increasingly wealthy third-world areas, but also in the industrialized areas, countries and individuals must work together to achieve controlled population growth. Carrying capacity is defined as the number of individuals of a certain species that can be sustained indefinitely in a particular area. The Earths capacity to support people is determined both by natural constraints and by human choices concerning economics, environment, culture (including values and politics), and demography. Human carrying capacity is more difficult to estimate than some of the standard demographic indicators, like expectation of life or the total fertility rate, because human carrying capacity depends on populations and activities around the world. Hum...
