It's the region of the world that leaves the biggest human footprint. It gobbles up 80 percent of the crop and other plant resources it produces each year. If things don't change, its ecological survival looks iffy.
Surprisingly, it's not the United States. It's a swath of Asia that sweeps from India to China. And it leads to a startling question: If these areas of the world are nearing an ecological budget deficit, can they sustain their growth much longer?
"Some regions of the world ... consume far beyond 100 percent of what their local ecosystems can provide," says Taylor Ricketts, director of the Conservation Science Program at the World Wildlife Fund in Washington, an author of a recent study on ecological imbalances. "These areas are being subsidized by other ecosystems. They're on a form of life support."
These findings stem from a map built by Dr. Ricketts and his colleagues which shows mankind's ecological footprint for each square mile of Earth's inhabited zones. This geographical representation, published in the journal Nature in June, defies conventional wisdom about consumption, while illustrating the dramatic effect of population density.
The calculation works this way: First, add up all the planet's sun energy converted to organic carbon by plants each year and call it "net primary production" or NPP - about 56 billion tons worth. Now, subtract the portion that human beings use - all the carbon in materials people consume from cotton in clothes to wood in homes to corn flakes and milk in a bowl of cereal.
Ricketts figures that the world's 6.3 billion people appropriate up to a third of the world's NPP a year. While that average sounds sustainable, it disguises key geographical imbalances (and ignores energy use and land-cultivation used in other human-footprint calculations).
For example, most of Siberia effectively uses 0 percent of its local NPP. By contrast, North America uses 23 percent. Surprisingly, that's still less than the worldwide average. North Americans aren't consuming less. They eat up 5.4 tons of carbon per year compared with a modest 1.2 tons for residents of south central Asia. But that part of Asia is far more populous - 1.3 billion people - and more densely packed than North America. As a result, that region consumes enough goods to require 1.6 billion tons of NPP per year or about 80 percent of the carbon output of that area, the study shows.
That's the present picture. If developing nations boost consumption to match industrialized countries, overall human appropriation of NPP would rise 75 percent, Ricketts and his group calculates.
That shift is already happening, argues Norman Myers, a visiting professor of environmental science at Oxford University and coauthor of a new book, "The New Consumers." More than 1 billion people in 20 developing and transitional nations have recently become wealthy enough to begin consuming like Americans. Already, they own one-fifth of the world's automobiles. By 2010, they could own a third. "The road the planet is heading down with all these new consumers will be enormously and gloriously unsustainable," Dr. Myers says in an telephone interview from Oxford, England. "If these consumers want to buy a lot of computers and gadgets - on the whole, that's OK.... But when it comes to cars, the environmental costs are huge."
Unlike Ricketts and company, Myers factors energy into his equation. Worldwide, the average human footprint is 2.28 hectares (5.4 acres), but Earth only has a biocapacity of 1.9 hectare per person, he says, citing a World Wildlife Fund Living Planet Report. That leaves a 0.38 hectare deficit per person.
In China, the deficit is more acute: 0.5 hectares per person. China's population is a major part of 1.1 billion new consumers worldwide with purchasing power equivalent to more than $6 trillion. Those consumers will buy as many as 800 million cars by 2010 and use a quarter of all electricity in their respective countries - generated by fossil fuels, Myers reports.
On the plus side, this consumer trend could be muted or reversed, he says. More efficient technologies could be adopted in developing nations - hybrid or electric-car technology instead of SUVs, for instance. And, there's also the possibility a different ethic, voluntary simplicity, could develop en masse along the way.
"Surveys show that a lot of people are finding that life doesn't get better with consumption of more and more goodies - that life should offer more than just another trip to the shopping mall," he says.
Not everyone is quite so concerned. Steven Hayward, a resident scholar with the American Enterprise Institute acknowledges models of global human consumption can be useful, but their predictions are often wrong in the long run. "They are essentially taking a static snapshot of the resource profile of the whole world," he says. "When you run that out in a straight line way, any snapshot will generally present an unsustainable conclusion."
For instance, a century ago the New England landscape had been turned into farm land and denuded of trees, which were burned for heat. Today, New England has been reforested. As the price of resources goes up, humanity will adjust, shift to other resources, he says.
At least some places take the consumption footprint issue seriously. By cutting its use of natural gas and diesel and increased recycling, Santa Monica, Calif. recently shrank its ecological footprint by 5.7 percent to 20.9 acres per person over 10 years, according to Redefining Progress, a nonprofit group focused on sustainability.
Unless that happens more broadly, though, humanity's footfall on the environment will get ever heavier, predicts Paul Ehrlich, a Stanford University professor of environmental studies. In his new book "One with Nineveh: Politics, Consumption, and the Human Future," he calls for a wholesale reassessment of human consumption.
In 2000, for instance, the US used about 23 percent of the world's energy despite having less than 5 percent of its population. The US has about one quarter of all the cars in the world. And much of its consumption affects other regions through its massive imports - cutting Indonesian forests, for instance.
"We humans are not living on our income, we are living on our capital - our agricultural soils, our underground water, and our biodiversity," Dr. Ehrlich says.
Humanity does have a chance to save itself, because population growth has moderated. Also, economists and ecologists are working to gauge the total costs of consumption more accurately. A $2 gallon of gasoline is really $6 because it carries $4 of unpaid environmental costs, he says. "We could do enormously better on energy efficiency with technologies we already have in hand.... Unfortunately, as far as consumption goes, we're still hog wild in the wrong direction."