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 ex-
pense of its surrounding environment by obtaining atoms from the Earth.
Consequently, the human biomass can never weigh more than the Earth; un-
less atoms are obtained from other planets, exponential growth cannot oc-
cur 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 gener-
ate more pollution. With a zero population growth, society could concen-
trate on improving environmentally benign technology while raising the
quality of goods and services. On the other hand, with an expanding popu-
lation, society must make use of its resources by providing new goods and
services for the growing population. For instance, instead of building fac-
tories, resources could be diverted to make the present ones more effi-
cient.

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