Scientists have recently found humanity's nitrogen footprint on
watersheds once thought to be isolated and pristine, indicating our
impact on the world is more widespread than previously imagined.
These findings show that natural nitrogen equilibriums have shifted
drastically and are now driven largely by human factors. This world
awash in nitrogen can have devastating effects on health, ecology and
the climate.
Nitrogen is an important element to all life as we know it. However,
its various forms are not equal in how they affect the environment.
Nitrous oxide, for example, is an especially potent greenhouse gas.
According to U.S. EPA, it is 300 times more powerful than carbon dioxide
at trapping heat, and it can stay in the atmosphere 300 years.
Meanwhile, nitrogen gas, which makes up close to 80 percent of the
air we breathe, is relatively inert. Other forms, like nitrates, form
aerosols in the atmosphere that can seed clouds, which generally have a
net cooling effect on the climate.
Nitrates, nitrites and nitrous oxide can arise naturally, or they
can come from human activities. Many of these compounds are byproducts
of combustion, whether in cars and trucks or factories and power plants.
The largest source, however, is agriculture. As the world's population
surges toward 7 billion people, many see nitrogen fertilizers as the
only way to increase crop yields enough to feed a hungry planet.
But what's really surprising is the scale of these impacts. According to a report published last month in the journal Science, researchers found that human activities produce more reactive nitrogen than all of nature combined.
"Almost certainly, more new fixed nitrogen and utilizable nitrogen
is produced by the sum total of human activity than by the sum total of
natural processes," said Alexander Wolfe, a professor of Earth sciences
at the University of Alberta, who co-authored the paper. "It turns out
the nitrogen cycle is more pervasively controlled by humanity" than
previously thought.
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