an carrying capacity is therefore dynamic and uncertain. Ecologists have often made use of the concept of carrying capacity in addressing the pressures that populations put on their environments. Many regions are already exceeding their carrying capacity; for example, cannot produce enough food to support their populations. One region where this is very clear is an enormous swath of equatorial Africa called the Sahel, that is undergoing very rapid desertification. The burgeoning populations of this area are contributing to its desertification by clearing forest for agriculture as well as for firewood. In 1900, 40% of Ethiopia was covered by forest; now only 4% is forested (Cohen, 1995).The earth does not contain enough resources to indefinitely sustain the current enormous population growth. For instance, there only is a limited area of arable land and living space available to us. China, home to 1.2 billion people or 1/5 the world's population, is an excellent example of the kinds of problems that arise in an increasingly crowded society. Trying to increase the standard of living of its people, China has industrialized and the economy has grown (Hanson, 1995). This increase in wealth has increased the demand for food in China. The demand is so great that China went from exporting 8 million tons of grain in 1992 to becoming a net importer of 16 million tons of grain in 1994 (China News Digest, 1995). This causes a worldwide grain shortage that raises prices, which in turn puts food out of reach of even more people. In many areas, there is simply not enough food to feed the growing populations. Each day 40,000 children die from malnutrition and its related diseases. 150 million children in the world suffer from poor health due to food shortages (Turbak, 1992). From the accounts taken of China and Japan, it may be fairly doubted whether the best-directed efforts of human industry can double the produce of the countries even...
