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 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".
Human activities are "destabilising the global environment", scientists are warning. Photo: Jonathan Carroll
They include the extinction rate; deforestation; the level of
carbon dioxide in the atmosphere; and the flow of nitrogen and
phosphorous (used on land as fertiliser) into the ocean.
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"What the science has shown is that human activities - economic
growth, technology, consumption - are destabilising the global
environment," said Will Steffen, who holds joint appointments at the
Australian National University and the Stockholm Resilience Centre, and
is the lead author of the paper.
These are not future problems,
but rather urgent matters, according to Professor Steffen, who said that
the economic boom since 1950 and the globalised economy have
accelerated the transgression of the boundaries.
Cleared land in Ecuador: the deforestation "boundary" has been crossed, scientists say. Photo: Bloomberg
No one knows exactly when push will come to shove, but he said
the possible destabilisation 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".
The flow of fertiliser chemicals into the ocean has reached a critical level, the paper says. Photo: Peter Braig
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."
Professor 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 civilisation 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 civilisation 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.
It's not just a list of Fs.
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 (ppm).
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 carbon dioxide 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.
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," Professor 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.
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 from these shocks.
"The planet is going to take care of itself. It's going to be here," Professor Richardson said.
Technology
can potentially provide solutions to many of the environmental problems
we face today. But technological innovations often come with unforeseen
consequences. Professor Pierrehumbert said we should be wary of
becoming too dependent on technological fixes for global challenges.
"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," he said.
"It becomes more and more like living on a spaceship than living on a planet."
The Washington Post
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