This article is from the In-Depth Report 7 Billion People and Counting

Population and Sustainability: Can We Avoid Limiting the Number of People?

Slowing the rise in human numbers is essential for the planet--but it doesn't require population control

The bitterness of the immigration debate has helped keep U.S. population growth off-limits in the national conversation. In industrial countries outside of North America, however, population is creeping back into public and even political consciousness. In the U.K., an all-party parliamentary panel issued a report called “Return of the Population Growth Factor” and called for stronger efforts to slow that growth. And the concern in the U.K. is not just about the people “over there” in developing countries. In early 2009 Jonathon Porritt, chair of the government’s Sustainable Development Commission, whacked a hornet’s nest by calling parents of more than two children “irresponsible” and blasting mainstream environmental groups for “betraying” their members by fearing to call for small families. “It is the ghost at the table,” Porritt said of population in an interview with the Daily Telegraph, a London broadsheet. Blog comments on his remarks, most of them supportive, soared into the thousands.

Meanwhile, in Australia, as summer temperatures hovered near 117 degrees Fahrenheit (47 degrees Celsius) and murderous flames converted forests into carbon dioxide, a new book entitled Overloading Australia: How Governments and Media Dither and Deny on Population issued an unusual ecological battle cry: ignore all admonitions to conserve the country’s
increasingly scarce water supplies until the government eliminates “baby bonuses” in the tax code and clamps down on immigration. A former premier of New South Wales spoke at the book’s launch.

With comments such as these gaining attention—and in some circles, approval—are environmentalists and eventually policy makers likely to renew the decades-old call for “population control”? Would they be wise to do so?

A Number of Us
Two big questions present themselves as population reemerges from the shadows: Can any feasible downshift in population growth actually put the environment on a more sustainable path? And if so, are there measures that the public and policy makers would support that could actually bring about such a change?

Nature, of course, couldn’t care less how many of us there are. What matters to the environment are the sums of human pulls and pushes, the extractions of resources and the injections of wastes. When these exceed key tipping points, nature and its systems can change quickly and dramatically. But the magnitudes of environmental impacts stem not just from our numbers but also from behaviors we learn from our parents and cultures. Broadly speaking, if population is the number of us, then consumption is the way each of us behaves. In this unequal world, the behavior of a dozen people in one place sometimes has more environmental impact than does that of a few hundred somewhere else.

Consider how these principles relate to global warming. The greenhouse gases already released into the atmosphere are likely to bring us quite close to the 3.6 degree F (two degree C) increase from the preindustrial global temperature average that many scientists see as the best-guess threshold of potential climate catastrophe. Already the earth is experiencing harsher droughts, fiercer storms and higher sea levels. If the scientists are right, these impacts will worsen for decades or centuries. Indeed, even if we ended all emissions tomorrow, additional warming is on the way thanks to the momentum built into the earth’s intricate climate system. (The oceans, for example, have yet to come into equilibrium with the extra heat-trapping capacity of the atmosphere. As the oceans continue to warm, so will the land around them.)

Our species’ demographic growth since its birth in Africa 200,000 years ago clearly contributed to this crisis. If world population had stayed stable at roughly 300 million people—a number that demographers believe characterized humanity from the birth of Christ to A.D. 1000 and that equals the population of just the U.S. today—there would not be enough of us to have the effect of relocating the coastlines even if we all drove Hummers. But instead we kept growing our numbers, which are projected to reach 9.1 billion by midcentury.

This article was originally published with the title "Population & Sustainability."

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