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BERKELEY, Calif. -- Humans need food. Humans use
energy. With these two basic truths, the Second International Nitrogen
Conference began last month in Maryland. But what does nitrogen have to do
with food and energy? And why should we care?
All living organisms need nitrogen to help
produce the amino acids and proteins essential to life. Nitrogen is a
tremendously abundant element, comprising 80 percent of the air we
breathe. But this atmospheric nitrogen is largely unusable by plants and
animals. Fortunately, natural processes -- such as the action of
microorganisms in our soil -- transform nitrogen into a form that plants
can use.
Every year, soil microorganisms
"fix" 140 million tons of nitrogen, thereby enabling plants to
grow and flourish. When plants die, some of that nitrogen is recycled back
into the atmosphere. This process of moving nitrogen from one form to
another is called the nitrogen cycle, and it's essential to all life.
People are part of this cycle too. We need
nitrogen, and we get it from our food -- both plants and animals. But we
are also changing the cycle, and as participants in the nitrogen
conference pointed out, it's causing tremendous amounts of pollution to
our air and water.
The problem is that people are fixing vast
quantities of nitrogen and releasing it into the environment. In fact,
humans now release almost twice as much available nitrogen every year as
do natural systems. About one-quarter of this amount is released through
burning fossil fuels, which creates nitrogen oxides, compounds that can
cause smog, global warming, and acid rain. But the majority of humanity's
excess nitrogen comes from synthetic nitrogen fertilizer used on farmers'
fields.
Synthetic fertilizer was first developed in
1913, but its use really took off in the 1960s during the "green
revolution," which doubled worldwide grain production. Synthetic
fertilizer enhances plant production by boosting the amount of fixed
nitrogen available in the soil. Today we use so much of this fertilizer
that excess nitrogen is leaching into groundwater, lakes, rivers, and
coastal waters. This leaching removes important nutrients from the soil,
reducing its fertility. It also pollutes groundwater and can cause an
excessive growth of plant life in surface water, leading to oxygen
depletion.
How big a problem is it? About 60 percent
of streams sampled in the United States show some signs of excess nitrogen
loading. The World Water Council, an independent association of water
scientists and engineers, recently reported that more than half of the
world's biggest fresh-water lakes are threatened by pollution or drainage
schemes. Coastal ecosystems are also affected. The Gulf of Mexico, for
example, contains a notorious oxygen-depleted "dead zone" caused
by agricultural runoff from the Mississippi River. In sum, ecologists at
the recent nitrogen conference say that the negative impact of excess
nitrogen in the environment ranks right up there with global warming.
But can we dump less nitrogen into the
environment without hurting food and energy production? It certainly seems
that way. Already, clean air laws in many countries have helped stabilize
the production of nitrogen oxides from burning fossil fuels. Europe leads
the way, with plans to reduce them by 40 percent in the next decade.
Reducing nitrogen leaking from farmer's
fields has so far not been as successful. Fertilizer is cheap and farmers
would rather apply too much, rather than too little, to ensure a bountiful
crop. But studies show that precision application of fertilizers can
reduce the amount of runoff and have little impact on crop yields. For
example, a study on the Mississippi River basin published in the journal
Nature found that reducing fertilizer use by just 12 percent would reduce
nitrogen runoff by 33 percent.
Yes, humans need food and humans use
energy. And nitrogen is a vital component to both of these needs. The key
is to find ways to meet these needs without compromising the long-term
health of the ecosystems that we also depend on. |