Almost two centuries ago, authors such as Thomas Malthus warned that overpopulation could threaten human welfare. More recently, such growth has been occurring at increasingly greater rates. Demographers now project that, if current trends continue, the world's inhabitants could number 8.5 billion within 35 years, and possibly well over 10 billion by the year 2050. Such growth will have adverse affects on both nonrenewable and renewable resources. Moreover, it is certain to cause severe degradation of the environment. Unless humans prove capable of controlling their own reproduction, the species, Homo sapiens, may ultimately be faced with its own extinction.
In 1987, the number of human beings living on the Earth passed the five billion mark. Since about 1600, human population growth has occurred at a "super exponential" rate. This means that in recent history the amount of time required for the population to double in size has become progressively smaller (Fischer 139 152). Thus, although the relative rate of population growth has decreased slightly, the annual increases in the sheer number of humans are still growing. At present, the world's population expands by over 90 million each year.
One of the primary causes of this growth is high rates of fertility. Such rates act like "compound interest applied to financial savings ("The environment" 1 31)." For example, a given couple and their offspring, all of whom believe in bearing four children (fertility rate of 4), will ultimately produce 64 great grandchildren (4x4x4=64). In contrast, if the same people only had two children per couple (fertility rate equal to 2), 8 great grandchildren would be produced (2x2x2=8). Hence, over time, small differences in fertility translate into huge differences in population size.
Currently, the global population is far from achieving a replacement level of fertility. Replacement levels can be defined as the number...