Global population reduction: confronting the inevitable.

• Author: Smail, J. Kenneth

Looking past the near-term concerns that have plagued population policy at the political level, it is increasingly apparent that the long-term sustainability of civilization will require not just a leveling-off of human numbers as projected over the coming half-century, but a colossal reduction in both population and consumption.

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It has become increasingly apparent over the past half-century that there is a growing tension between two seemingly irreconcilable trends. On one hand, moderate to conservative demographic projections indicate that global human numbers will almost certainly reach 9 billion, perhaps more, by mid-21st century. On the other, prudent and increasingly reliable scientific estimates suggest that the Earth's long-term sustainable human carrying capacity, at what might be defined as an "adequate" to "moderately comfortable" developed-world standard of living, may not be much greater than 2 to 3 billion. It may be considerably less, particularly if the normative lifestyle (level of consumption) aspired to is anywhere close to that of the United States.

As a consequence of this modern-day "Malthusian dilemma," it is past time to think boldly about the midrange future and to consider alternatives that go beyond merely slowing or stopping the growth of global population. The human species must develop and quickly implement a well-conceived, clearly articulated, flexible, equitable, and internationally coordinated program focused on bringing about a very significant reduction in human numbers over the next two or more centuries. This effort will likely require a global population shrinkage of at least two-thirds to threefourths, from a probable mid-to-late 21st century peak in the 9 to 10 billion range to a future (23rd century and beyond) "population optimum" of not more than 2 to 3 billion.

Obviously, a demographic change of this magnitude will require a major reorientation of human thought, values, expectations, and lifestyles. There is no guarantee that such a program will be successful. But if humanity fails in this effort, nature will almost certainly impose an even harsher reality. As a practicing physical anthropologist and human evolutionary biologist, I am concerned that this rapidly metastasizing (yet still partly hidden) demographic and environmental crisis could emerge as the greatest evolutionary/ecological "bottleneck" that our species has yet encountered.

Although the need for population reduction is...