To the Editor:

Re “Overpopulation Is Not the Problem” (Op-Ed, Sept. 14):

Erle C. Ellis recounts his transition from a narrow, distorted biological determinism regarding the challenges facing the human population to a narrow, distorted social-scientific optimism that “the only limits to creating a planet that future generations will be proud of are our imaginations and our social systems.”

Both extreme positions ignore the more complex reality that human choices interact with natural constraints.

The biology, chemistry and physics of the earth are imperfectly understood. It is not possible to predict precisely what some human choices may lead to, or whether some future environmental changes may be beyond human control. It is clear, however, that every additional billion people constrain further the choices available for life on earth, human and otherwise.

Continued rapid human population growth makes it harder and more costly to solve all our problems. The institutional, technological and behavioral innovations that have a chance of leading to the rosy future Mr. Ellis envisions will happen only with substantial effort and investment, and will be easier with slower or no population growth.