The journal Science published an article online today that says civilization has crossed four of nine “planetary boundaries” due to human activity. According to an international team of 18 researchers, climate change, the loss of biosphere integrity, land-system change, and altered biogeochemical cycles (like phosphorus and nitrogen runoff) have all passed beyond levels that put humanity in a “safe operating space.”
The article is entitled, “Planetary Boundaries: Guiding human development on a changing planet,” and is available online on the Science Express website.
Steve Carpenter, director of the Center for Limnology at the University of Wisconsin-Madison, is one of the report’s authors. He says the study should be a wake up call to policymakers that “we’re running up to and beyond the biophysical boundaries that enable human civilization as we know it to exist.”
For the last 11,700 years, Earth has been in a “remarkably stable state,” says Carpenter. During this time, known as the Holocene epoch, “everything important to civilization,” has occurred. From the development of agriculture, to the rise and fall of the Roman Empire, to the Industrial Revolution, the Holocene has been a good time for human endeavors. But, over the last century, some of the parameters that made the Holocene so hospitable have changed.
Climate change, of course, is one of those things, as is a troubling loss of biodiversity. But Carpenter’s contribution to the report has to do with two elements essential to life – the chemical elements phosphorus and nitrogen.
Both phosphorus and nitrogen are widely used to fertilize crops and the rise of large-scale, industrial agriculture has led to an immense increase in the amount of the chemicals entering our ecosystems. “We’ve changed nitrogen and phosphorus cycles vastly more than any other element,” Carpenter says. “[The increase] is on the order of 200 to 300 percent. In contrast, carbon has only been increased ten to twenty percent and look at all the uproar that has caused in [the] climate.”
The increase of phosphorus and nitrogen has been especially detrimental to water quality. Phosphorus loading is the leading cause of both harmful algal blooms and the oxygen-starved “dead zone” in Lake Erie. Likewise, nitrogen flowing down the Mississippi River is the main culprit behind the “dead zone” in the Gulf of Mexico.
The bottom line is that nitrogen and phosphorus levels are way beyond the boundaries of what they were during the Holocene. But, Carpenter says, that chemical load isn’t spread evenly over the planet.
“The are places that are really, really overloaded with nutrient pollution,” he says. “Wisconsin and the entire Great Lakes region are some of those. But there are other places where billions of people live that are undersupplied with nitrogen and phosphorus.” Much of Africa is largely undersupplied with these two essential elements. “We’ve got certain parts of the world that are over-polluted with nitrogen and phosphorus, and others where people don’t even have enough to grow the food they need.”
Carpenter calls it a “distribution problem” and says that places like the Midwestern U.S. could vastly reduce its use of fertilizers and still maintain productive crops while nutrient poor regions of the globe increased their use, all while keeping the global levels safely within the study’s prescribed “planetary boundary.”
“It might be possible for human civilization to live outside Holocene conditions, but it’s never been tried before,” Carpenter says. “We know civilization can make it in Holocene conditions, so it seems wise to try to maintain them.”
Researchers will discuss the study next week at the World Economic Forum in Davos, Switzerland.
An abstract of the paper can be found here: http://www.sciencemag.org/lookup/doi/10.1126/science.1259855
The full article is available on the Science Express website: http://www.sciencexpress.org
Discussions about the planetary boundaries started in 2008 at a workshop convened by the Stockholm Resilience Centre, Stockholm Environment Institute and the Tällberg Foundation. The results of that were the two original studies:
“A safe operating space for humanity” (Nature) 24 September 2009.
“Planetary boundaries: exploring the safe operating space for humanity“, Ecology and Society, 14 (2), 32.
Steve Carpenter, UW-Madison, firstname.lastname@example.org, 608-262-3014 (U.S.),
Fredrik Moberg, communications, Stockholm Resilience Centre (Sweden) Fredrik.email@example.com, +43-(0)70-680-6553
Imagery available upon request.