Planetary Boundaries: A Safe Operating Space for Humanity

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"Big Question: Is Earth Past the Tipping Point?" - video produced by the Institute on the Environment
"Boundaries for a Healthy Planet" - the cover story in Scientific American's April 2010 issue, co-written by Jon Foley

MINNEAPOLIS / ST. PAUL (9/23/2009) -- Over the past century, human activity has changed the global environment more than any natural process in Earth’s recent history. Due to such massive, human-caused change, many parts of the planet are quickly approaching a breaking point.

In response, an international team of researchers has taken the first step toward defining a “safe planetary operating space” that will guide civilization into a secure and sustainable future.

In the article “Planetary Boundaries: A Safe Operating Space for Humanity”—published Sept. 24 in the journal Nature—28 leading scientists attempt to quantify the safe biophysical boundaries outside which, they believe, Earth’s natural systems can no longer function in a stable state. Contributors from the University of Minnesota include Jonathan Foley, director of the Institute on the Environment, and Peter Snyder, an IonE associate fellow and assistant professor in the department of soil, water and climate.

Human pressures on the planet have reached a scale where abrupt global environmental “tipping points” can no longer be ignored, says lead author Johan Rockström, director of the Stockholm Resilience Centre at Stockholm University.

“To continue to live and operate safely, humanity has to stay away from critical thresholds in Earth’s environment and respect the nature of our planet’s climatic, geophysical, atmospheric and ecological processes,” Rockström explains.

The article introduces important thresholds and boundaries that humans must recognize to avoid irreversible, and potentially catastrophic, changes to the global environment. The nine boundaries include climate change; stratospheric ozone; land use change; freshwater use; biological diversity; ocean acidification; nitrogen and phosphorus inputs to the biosphere and oceans; aerosol loading; and chemical pollution.

We may have already crossed three of these boundaries, according to the authors. Perhaps the most recognized among them is climate change. “Observations of a climate transition include the rapid retreat of summer sea ice in the Arctic Ocean, the melting of almost all mountain glaciers around the world, and an increased rate of sea-level rise in the past 10-15 years,” says co-author John Schellnhuber, director of the Potsdam Institute for Climate Impact Research.

The University of Minnesota’s Foley points to another example: Through fertilizers and industrial pollution, we’ve already doubled the natural cycling of nitrogen and phosphorus globally. “And we may need to double that amount again to feed 3 billion more people in the next 40 years,” he says. “How long until the whole system unravels?”

The authors also emphasize that the boundaries are interconnected: Crossing one may threaten the ability to stay within safe levels of the others.

“Everything we’ve based the success of our civilization on, including agriculture, coastlines, patterns of weather, could be severely disrupted,” says Foley. “It wouldn’t be the end of the world, but it would be the end of the world as we know it.”

While the planetary boundaries aren’t 100 percent definitive, they do serve as a preliminary map. The authors hope the next generation of scientists will refine and perfect the ideas in the Nature article.

“What we present is a novel framework through which our scientific understanding of Earth’s systems can potentially be used more directly in the societal decision-making process,” says co-author Katherine Richardson, a professor at the University of Copenhagen’s Earth System Science Center.

“Imagine you’re driving on top of a mesa at night, without headlights, and you’re stomping on the accelerator. You probably want to know where the edge is,” says Foley. “This paper is the first attempt to show where the edges of the cliff are. They’re not that far away.”

More info:
Exclusive feature coverage, commentaries and more at Nature News
Full article, video interviews, graphics and background materials

Sources:
U.S. - Jonathan Foley, 612-626-3749
EUROPE - Johan Rockström, John Schellnhuber, Katherine Richardson
AUSTRALIA - Will Steffen