Scientists:
Human activity has pushed Earth beyond four of nine ‘planetary
boundaries’
15
January, 2015
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.
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.
Forest cover and land system change: Farming, mining and infrastructure projects are consuming the Amazon rainforest. According to data from Brazil’s space agency, deforestation increased by more than a third in 2013, wiping out an area more than twice the size of Los Angeles. (Nacho Doce/Reuters)
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.
Beyond
each planetary boundary is a “zone of uncertainty.” This zone is
meant to acknowledge the inherent uncertainties in the calculations,
and to offer decision-makers a bit of a buffer, so that they can
potentially take action before it’s too late to make a difference.
Beyond that zone of uncertainty is the unknown — planetary
conditions unfamiliar to us.
“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.
Pierrehumbert, who was not involved in the paper published in Science, added that a planetary boundary “is like an avalanche warning tape on a ski slope.”
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.
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.”
The authors make clear that their goal is not to offer solutions, but simply to provide information. This is a kind of report card, exploiting new data from the past five years.
Atmosphere aerosol loading: Emissions spew from smokestacks at a Kansas coal-fired power plant. (Charlie Riedel/AP)
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.
This
young field of research draws from such disciplines as ecology,
geology, chemistry, atmospheric science, marine biology and
economics. It’s known generally as Earth Systems Science. The
researchers acknowledge the uncertainties inherent in what they’re
doing. Some planetary boundaries, such as “introduction of novel
entities” — CFCs would be an example of such things — remain
enigmatic and not easily quantified.
Better
understood is the role of carbon dioxide as a greenhouse gas. The
safe-operating-zone boundary for CO2 had previously been estimated at
levels up to 350 parts per million. That’s the boundary — and
we’re already past that, with the current levels close to 400 ppm,
according to the paper. That puts the planet in the CO2 zone of
uncertainty that the authors say extends from 350 to 450 ppm.
At
the rate CO2 is rising — about 2 ppm per year — we will surpass
450 ppm in just a couple of decades, said Katherine Richardson, a
professor of biological oceanography at the University of Copenhagen
in Denmark and a co-author of the new paper.
Biogeochemical flows: Rows of corn wait to be harvested in Minooka, Ill. Fertilizer makes its ways to the ocean via surface runoff or seeping into the ground and groundwater. (Jim Young/Reuters)
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.
Species extinction: 14-week-old twin polar bear cubs play in Munich. Polar bears, the largest predator on Earth, are struggling to survive due to melting ice and depletion of its food source — seal blubber. (Alexandra Beier/Getty Images)
A baby mountain gorilla in the Sabyinyo Mountains of Rwanda: Mountain gorillas are an endangered species found only in the border areas of Rwanda, Uganda and the Democratic Republic of the Congo. (Ivan Lieman/AFP/Getty Images)
A kaleidoscope of Monarch butterflies clings to tree branches in the Piedra Herrada, near Valle de Bravo, Mexico. Unusually cold temperatures and the threat to its food supply — milkweed — worry scientists. (Rebecca Blackwell/AP)
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.
“There’s
a lot of emotion involved in this. If you think about it, the
American ethic is, ‘The sky’s the limit.’ And here you have
people coming on and saying, no it isn’t, the Earth’s the limit,”
she said.
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.”
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