Unprecedented levels of carbon dioxide in the atmosphere, widespread species extinction and deforestation, and high levels of nitrogen and phosphorous in the oceans because of fertilizer use are putting humanity beyond thresholds that scientists say are safe for the continuation of life on Earth, according to new researched published in the journal Science. The rate at which humans are degrading the environment, they continue, is unprecedented in the past 11,700 years.
"The way to interpret this is as a warning sign," Steve Carpenter, a professor of zoology at the University of Wisconsin-Madison, told VICE News. "We're running up to the biophysical boundaries that enable human civilization as we know it to exist."
In 2009, a group of 28 scientists from around the world came together to create the "planetary boundaries framework," which identified nine processes that need to be monitored in order to maintain life on Earth. The processes were ozone depletion, biodiversity loss, chemical pollution, climate change, ocean acidification, freshwater composition, land systems change, nitrogen and phosphorous flows, and atmospheric aerosol loading. Crossing the recommended thresholds for any of these processes could generate abrupt and possibly irreversible environmental changes.
Humans have surpassed the safe threshold for four of these boundaries, researchers say.
Carbon dioxide levels are at historic highs, say the authors, hovering around 400 parts per million, a level scientists warn is radically altering the Earth's atmosphere and oceans. Some 46,000-58,000 square miles of forest are felled each year. Species are going extinct at a rate more than 100 times faster than has occurred historically. And, fertilizer use, which has boosted agricultural yields, has also reached an all-time high but when carried by wind or water into rivers and oceans makes them uninhabitable for aquatic species.
"Within Earth systems, the boundaries are intertwined," Carpenter told VICE News. "For example, phosphorous and nitrogen cause tremendous harm to freshwater resources. We also know that phosphorous and nitrogen affects the carbon cycle."
Kieran Suckling, Executive Director of the Center for Biological Diversity, said the study is invaluable in conveying to the public and politicians the urgency in changing the way humans interact with the environment.
"Most of the time people think of environmental problems, like species extinction, in linear steps," Suckling told VICE News. "You get the impression that you could dial it back at any time and solve all the problems. But this study shows that the problems are not linear. If you inflict enough damage, you've shifted the planet into a whole new state and the damage spirals out of control."
Suckling said that the report shows that much more aggressive environmental policy on conservation and mitigating climate change is necessary.
"It's kind of like you've stepped off the curb. You're not going to get hit by a car immediately, but there is danger," Carpenter told VICE News. "We don't recommend any policy in our report but the policy conversation is going to be really important."
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