The Environmental Concern for Overpopulation
Presently, the human population is increasing exponentially at the rate of approximately 1.5 percent annually. If this growth rate were to continue, one can imagine that the sheer mass of all living humans, in a few thousand years, would be greater than the mass of the Earth. In order for the human biomass to mushroom to this level, it would need to devour the Earth itself. Planet Earth is essentially a closed system with respect to matter. There is no transfer of matter between the Earth and its surroundings. Because the number of atoms on Earth is finite, a species grows in biomass at the expense of its surrounding environment by obtaining atoms from the Earth. Consequently, the human biomass can never weigh more than the Earth; unless atoms are obtained from other planets, exponential growth cannot occur on Earth forever.
This population explosion, in many respects, is one of the rudimentary causes of environmental problems. Holding all other variables constant, humans will eventually affect the environment; larger populations will consume enormous quantities of resources and will subsequently generate more pollution. With a zero population growth, society could concentrate on improving environmentally benign technology while raising the quality of goods and services. On the other hand, with an expanding population, society must make use of its resources by providing new goods and services for the growing population. For instance, instead of building factories, resources could be diverted to make the present ones more efficient.