Worst Threat to Earth? Way Too Many People

With the number of humans on Earth expected to reach 9.5 billion by the second half of the 21st century, policymakers and environmentalists should turn their attention to the grave dangers of overpopulation and overconsumption, Paul Ehrlich—author of 1968 bestseller The Population Bomb—and wife Anne write in Yale Environment 360. Population growth, above all other ecological hazards, may lead to the collapse of our civilization.

Political and science leaders "are under the delusion that such a disastrous end to the modern human enterprise can be avoided by technological fixes," the Ehrlichs point out. But while adopting fuel-efficient cars and increasing recycling might prove beneficial in the short term, "there is no technological change we can make that will permit growth in either human numbers or material affluence to continue to expand." (More overpopulation stories.)