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Humans Consume More Than Earth Can Replace, Study Says

June 25, 2002|GARY POLAKOVIC | TIMES STAFF WRITER

Humans now consume more of the Earth's natural resources than the planet can replace, raising doubts about the long-range sustainability of modern economies, according to a new study being published in the Proceedings of the National Academy of Sciences.

For the last 20 years, people have been depleting natural resources, including fish, forests and arable land, at a rapid rate. Economic expansion has boosted demand for resources and overshot the planet's ability to regenerate them by 20%, the study says.

"You can overdraw on nature's accounts and leave a debt. We are no longer living off nature's interest, but nature's capital. Sustainable economies are not possible if we live beyond the means of nature," said Mathis Wackernagel, lead author of the study and sustainability program director for Oakland-based Redefining Progress, a nonprofit public policy group.

The study, titled "Tracking the Ecological Overshoot of the Human Economy," was produced by an international team of researchers and will be published this week. It marks the first attempt to build a comprehensive accounting method to assess the cost borne by nature of human activity.

The latest study is part of a growing body of work that attempts to calculate the cost to the environment of a variety of human activities, not just of a product in a marketplace.

In estimating the "ecological footprint" of humanity, the authors looked at six activities over the past 40 years, calculated how much land and biological production is devoted to those activities and how much is needed to sustain them. The researchers looked at growing crops for food and other products; grazing animals for meat, milk and wool; logging; fishing; providing space and materials for houses, highways, dams and industries; and fossil fuel burning.

According to their analysis, human demand has been outstripping nature's ability to resupply since the early 1980s. Since 1961, human demand on resources has nearly doubled and today exceeds the Earth's replacement capacity by 20%, the researchers found.

Much of the impact is in the area of fossil fuel use. For example, energy consumption has increased so much over the past 40 years that it takes about five times more land mass to produce fossil fuels and absorb carbon-based emissions. Indeed, at the heart of the concern over global warming is the fact that more carbon is being produced than the planet can capture.

Today, it takes at least 5.75 acres of land to sustain one average person on Earth, although it takes nearly twice that much to support one European and nearly four times that much to support one American, the study shows.

"You can debate any one of these measurements, but whenever scientists look at this issue they come up with very disturbing answers," said Sierra Club Executive Director Carl Pope. "We are not on a sustainable path and these measures show us the situation is getting worse and we should be concerned and start taking action."

But critics have challenged the assumptions behind such studies. They note that technological breakthroughs and better land-use practices can make farms, factories and power plants, among others, more efficient.

Furthermore, while the study compares consumption with the Earth's replacement capacity, it does not factor in the large holdings of natural resources effectively kept in reserve. How long that "natural capital" can withstand being overdrawn is an open question.

Wackernagel said the purpose of the study was to provide business and government leaders a clearer idea of the ecological costs of human activity and economic expansion. "We're not saying this is inevitable, but if we don't have accounts of nature, it's the same as a business that doesn't know how much it spends and earns," he said.

Eleven researchers from six nations participated in the study.

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