Scientists: Human activity has pushed Earth beyond four of nine ‘planetary boundaries’

Summary

At the rate things are going, the Earth in the coming decades could cease to be a “safe operating space” for human beings. That is the conclusion of a new paper published Thursday in the journal Science by 18 researchers trying to gauge the breaking points in the natural world.

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The paper contends that we have already crossed four ‘planetary boundaries’. They are the extinction rate; deforestation; the level of carbon dioxide in the atmosphere; and the flow of nitrogen and phosphorous (used on land as fertilizer) into the ocean.

‘What the science has shown is that human activities — economic growth, technology, consumption — are destabilizing the global environment,’ said Will Steffen, who holds appointments at the Australian National University and the Stockholm Resilience Center and is the lead author of the paper.

These are not future problems, but rather urgent matters, according to Steffen, who said that the economic boom since 1950 and the globalized economy have accelerated the transgression of the boundaries. No one knows exactly when push will come to shove, but he said the possible destabilization of the ‘Earth System’ as a whole could occur in a time frame of ‘decades out to a century.’

The researchers focused on nine separate planetary boundaries first identified by scientists in a 2009 paper. These boundaries set theoretical limits on changes to the environment, and include ozone depletion, freshwater use, ocean acidification, atmospheric aerosol pollution and the introduction of exotic chemicals and modified organisms

‘The boundary is not like the edge of the cliff,’ said Ray Pierrehumbert, an expert on Earth systems at the University of Chicago. ‘They’re a little bit more like danger warnings, like high-temperature gauges on your car.’

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The scientists say there is no certainty that catastrophe will follow the transgression of these boundaries. Rather, the scientists cite the precautionary principle: We know that human civilization has risen and flourished in the past 10,000 years — an epoch known as the Holocene — under relatively stable environmental conditions.

No one knows what will happen to civilization if planetary conditions continue to change. But the authors of the Science paper write that the planet ‘is likely to be much less hospitable to the development of human societies.’

It’s not just a list of F’s. The ozone boundary is the best example of world leaders responding swiftly to a looming environmental disaster. After the discovery of an expanding ozone hole caused by man-made chemicals, chlorofluorocarbons, the nations of the world banned CFCs in the 1980s.

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Humanity may have run into trouble with planetary boundaries even in prehistoric times, said Richard Alley, a Penn State geoscientist who was not part of this latest research. The invention of agriculture may have been a response to food scarcity as hunting and gathering cultures spread around, and filled up, the planet, he said. “It’s pretty clear we were lowering the carrying capacity for hunter-gatherers 10,000 years ago,” Alley said.

There are today more than 7 billion people, using an increasing quantity of resources, turning forest into farmland, boosting the greenhouse gases in the atmosphere and driving other species to extinction. The relatively sudden efflorescence of humanity has led many researchers to declare that this is a new geological era, the human age, often referred to as the Anthropocene.

Human activity

The Earth has faced shocks before, and the biosphere has always recovered. Hundreds of millions of years ago, the planet apparently froze over — becoming ‘Snowball Earth.’ About 66 million years ago, it was jolted by a mountain-sized rock from space that killed half the species on the planet, including the non-avian dinosaurs. Life on Earth always bounced back.

‘The planet is going to take care of itself. It’s going to be here,’ Richardson said.

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Technology can potentially provide solutions, but innovations often come with unforeseen consequences. ‘The trends are toward layering on more and more technology so that we are more and more dependent on our technological systems to live outside these boundaries,’ Pierrehumbert said. ‘. . . It becomes more and more like living on a spaceship than living on a planet.’

Read the full article on Washingtonpost.com

Photo © nvelichko via shutterstock / Nacho Doce  – Reuters / Charlie Riedel – AP