Now he is warning that the earth is running out of oil, coal, oxygen, forests, farmland and rangeland and suggests urgent measures.
Mongolian population expert Yutha Naja has called for United Nations police to capture people in the most heavily populated countries and force them to undergo sterilization.
"We have too many Indians, too many Africans and too many Asians," Naja said. "And if we don't do anything about it, we'll have way, way too many."
David Brower, Friends of the Earth, said bearing children should be a crime unless the parents hold a license to reproduce. He said all potential parents should be "required to use contraceptive chemicals, the government issuing antidotes to citizens chosen for childbearing.”
Cher Ruskin Head, United Nations overpopulation czar, who shares a husband with a German supermodel, said citizens who are likely to bear children with genetic disorders should be barred from reproducing altogether.
"Jews, blacks, hemophiliacs, albinos, ADD sufferers, people who are too short or too tall or too fat, alcoholics, drug addicts and any other person whose offspring are likely to be a drain on society should be neutered by coercion," she said.
An opponent of her proposal is Jean Poole of the Concerned Climate Change Professionals (CCCP), who said the first population reductions should take place in the United States because Americans use more resources per capita than any other nation.
"I don't think we could persuade the government to start thinning out people," she said. "But we can start fighting things that keep people alive longer than necessary. We must stop funding cancer research, for one thing. Cancer is nature's way of trimming the population. Also, we should fight to repeal seat belt laws, drunk driving laws, motorcycle helmet laws and other regulations that are artificially allowing humans to live too long."
Senna Sayid of the Indian Subcontinent Overpopulation Bureau (I-SOB) said socialized medical care could reduce the average life span of humans, which would go a long way toward ameliorating the impacts of excessive reproduction. She said poor people in her homeland of India as well as throughtout the earth have life spans about 30 years shorter than wealthy people.
"The problem is that people with money can afford better medical care," she said, "and so they live longer. Under socialized medicine money no longer determines who gets the best care. It is in government's best interest to give the best care to young workers who have many years of productivity remaining, not the old who are leeches on society.
"Under the best system, death should be planned to coincide with the end of a person's productive working life. My colleagues and I have been pushing for a maximum life span of 50."