During the 352-year life span of the Royal Society, the human population has risen from less than one billion people to seven billion and counting. That boom has been supported by science and technology—Watt's coal-fired steam engine, Haber and Bosch synthesizing nitrogen fertilizer, Fleming's discovery of penicillin—and continues today as the world's population expands at the rate of 78 million people per year.

Now the Royal Society wants the world to do something about population growth in a bid to stave off environmental and economic calamity, according to a new report dubbed "People and the Planet" released on April 26. At the same time, the excessive consumption of the world's richest billion people must be restrained so that pets in the U.S. don't consume more resources than people in Bangladesh.

The human economy (as measured by gross domestic product) has quadrupled in the past 50 years, outpacing even the rate of population growth. More recently China, India and other emerging economies have lifted millions out of poverty and begun to afford to some of their citizens the material affluence enjoyed by citizens in Europe, Japan and the U.S. And yet more than a billion people around the world still live in absolute poverty (and have the highest fertility rates).

The impact of the twin perils of population numbers and excessive consumption is readily apparent, and includes climate change from fossil fuel burning and land clearing, oceanic dead zones proliferating thanks to fertilizer runoff, and a sixth mass extinction of other species as we leave less and less room for other life. The list will get longer as we proceed deeper into what geologists are beginning to call the Anthropocene, or age of man. We have become a geologic force.

So how can the world balance the need for economic growth and forestall ecological disaster? A team of 23 scientists convened by the Royal Society spent the last 21 months puzzling over the conundrum. The resulting report calls for population and consumption to be considered together rather than separately by the world's governments as they move to embrace sustainability and lists three in-no-way-surprising recommendations:

(1) The poorest people will require more—better everything, or as the scientists put it "increased per capita consumption," but that means that

(2) Developed and even emerging economies will have to cut back. Yes, the Royal Society is calling for a global rebalancing of wealth. Oh, and more recycling. Finally,

(3) "global population growth needs to be slowed and stabilized," though this should not be "coercive." In other words, there is an urgent need for more free birth control, if not one-child policies. The scientists recommend putting population on the agenda for the upcoming United Nations environmental summit in Rio de Janeiro in June.

Here is the good news: everything the scientists call for is to some extent already happening. Population growth peaked in the 1960s and has been declining ever since. Education of women, whenever and wherever it occurs, boosts incomes, restrains fertility and even increases farming output, among other positives. There is literally no downside to the empowerment of women that is even remotely detectable. At the same time, the flight of much of the world's population to cities —emerging economies are adding the equivalent of a million-person city every five days—may help reduce the global impacts of the extended family of man. The trick will be ensuring that new cities are built right and old cities get the right retrofits, all while improving agriculture (particularly reducing waste).

Yet managing a transition to some form of just, low-impact global economy is not going to be easy. The right choices need encouragement, the wrong ones disparagement. After all, we rich may simply decide to move from trashing this finite planet to trashing asteroids, moons and even other worlds instead. Scientists, for their part, will have to take over management of natural ecosystems on the only spaceship known to offer a comfortable home to humanity to ensure they continue to provide the services, like clean water, we all rely on to survive. And humanity will have to make smart use of its oldest talent—adaptability—to cope with the changes we have brought on ourselves. Otherwise, the "age of man" may prove quite inhospitable to man.

The fear promoted by this Royal Society report is one of economic and ecological disaster if the twin perils of consumption and population are not addressed through restriction. Of course, most of that population growth is not happening in countries the scientists formulating the report hail from, but rather in the least developed countries, the bulk of which are in Africa. Fears of the wrong sort of population growth have a long dark, history, but actual history suggests that an excess of humanity can actually be a good thing, providing the renewable resource of human ingenuity that then fuels economic development (and world-changing scientific ideas). Plus, there is the troubling question of: what number is the right number, who decides and who enforces it? As the Royal Society's motto goes "take nobody's word for it." Not even the Royal Society's.