The Great Lakes Zephyr - Wind Energy & Hydrogen Journal

Eco-Economy Update 2004-10
For Immediate Release
Copyright Earth Policy Institute 2004
June 16, 2004


DEAD ZONES INCREASING IN WORLD'S COASTAL WATERS
http://www.earth-policy.org/Updates/Update41.htm

Janet Larsen


As summer comes to the Gulf of Mexico, it brings with it each year a giant
"dead zone" devoid of fish and other aquatic life. Expanding over the past
several decades, this area now can span up to 21,000 square kilometers,
which is larger than the state of New Jersey. A similar situation is found
on a smaller scale in the Chesapeake Bay, where since the 1970s a large
lifeless zone has become a yearly phenomenon, sometimes shrouding 40
percent of the bay.

Worldwide, there are some 146 dead zones--areas of water that are too low
in dissolved oxygen to sustain life. Since the 1960s, the number of dead
zones has doubled each decade. Many are seasonal, but some of the
low-oxygen areas persist year-round.

What is killing fish and other living systems in these coastal areas? A
complex chain of events is to blame, but it often starts with farmers
trying to grow more food for the world's growing population. Fertilizers
provide nutrients for crops to grow, but when they are flushed into rivers
and seas they fertilize microscopic plant life as well. In the presence of
excessive concentrations of nitrogen and phosphorus, phytoplankton and
algae can proliferate into massive blooms. When the phytoplankton die,
they fall to the seafloor and are digested by microorganisms. This process
removes oxygen from the bottom water and creates low-oxygen, or hypoxic,
zones.

Most sea life cannot survive in low-oxygen conditions. Fish and other
creatures that can swim away abandon dead zones. But they are still not
entirely safe--by relocating they may become vulnerable to predators and
face other stresses. Other aquatic life, like shellfish, that cannot
migrate in time suffocate in low-oxygen waters.

Dead zones range in size from small sections of coastal bays and estuaries
to large seabeds spanning some 70,000 square kilometers. Most occur in
temperate waters, concentrated off the east coast of the United States and
in the seas of Europe. Others have appeared off the coasts of China,
Japan, Brazil, Australia, and New Zealand.

The world's largest dead zone is found in the Baltic Sea, where a
combination of agricultural runoff, deposition of nitrogen from burning
fossil fuels, and human waste discharge has overfertilized the sea.
Similar problems have created hypoxic areas in the northern Adriatic Sea,
the Yellow Sea, and the Gulf of Thailand. Offshore fish farming is another
growing source of nutrient buildup in some coastal waters.

Forty-three of the world's known dead zones occur in U.S. coastal waters.
The one in the Gulf of Mexico, now the world's second largest, disrupts a
highly productive fishery that provides some 18 percent of the U.S. annual
catch. Gulf shrimpers and fishers have had to move outside of the hypoxic
area to find fish and shrimp. Landings of brown shrimp, the most
economically important seafood product from the Gulf, have fallen from the
record high in 1990, with the annual lows corresponding to the highly
hypoxic years.

Excess nutrients from fertilizer runoff transported by the Mississippi
River are thought to be the primary cause of the Gulf of Mexico's dead
zone. Each year some 1.6 million tons of nitrogen now enter the Gulf from
the Mississippi basin, more than triple the average flux measured between
1955 and 1970. The Mississippi River drains 41 percent of the U.S.
landmass, yet most of the nitrogen originates in fertilizer used in the
productive Corn Belt.

Worldwide, annual fertilizer use has climbed to 145 million tons, a
tenfold rise over the last half-century. (See data at
http://www.earth-policy.org/Updates/Update41_data.htm ) This coincides
with the increase in the number of dead zones around the globe. And not
only has more usable nitrogen been added to the environment each year, but
nature's capacity to filter nutrients has been reduced as wetlands are
drained and as areas along riverbanks are developed. Over the last
century, the world has lost half its wetlands.

In the United States, some of the key farming states like Ohio, Indiana,
Illinois, and Iowa have drained 80 percent of their wetlands. Louisiana,
Mississippi, Arkansas, and Tennessee have lost over half of theirs. This
lets even more of the excess fertilizer farmers apply flow down the
Mississippi River to the gulf.

There is no one way to cure hypoxia, as the mix of contributing factors
varies among locations. But the keys are to reduce nutrient pollution and
to restore ecosystem functions. Fortunately, there are a few successes to
point to. The Kattegat straight between Denmark and Sweden had been
plagued with hypoxic conditions, plankton blooms, and fish kills since the
1970s. In 1986, the Norway lobster fishery collapsed, leading the Danish
government to draw up an action plan. Since then, phosphorus levels in the
water have been reduced by 80 percent, primarily by cutting emissions from
wastewater treatment plants and industry. Combined with the
reestablishment of coastal wetlands and reductions of fertilizer use by
farmers, this has limited plankton growth and raised dissolved oxygen
levels.

The dead zone on the northwestern shelf of the Black Sea peaked at 20,000
square kilometers in the 1980s. Largely because of the collapse of
centralized economies in the region, phosphorus applications were cut by
60 percent and nitrogen use was halved in the Danube River watershed and
fell similarly in other Black Sea river basins. As a result, the dead zone
shrank. In 1996 it was absent for the first time in 23 years. Although
farmers sharply reduced fertilizer use, crop yields did not suffer
proportionately, suggesting they had been using too much fertilizer
before.

While phosphorus appears to have been the main culprit in the Black Sea,
nitrogen from atmospheric sources--namely, emissions from fossil fuel
burning--seems to be the primary cause of the dead zones in the North and
Baltic seas. Curbing fuel use through efficiency improvements,
conservation, and a move toward renewable energy can diminish this cause
of the problem.

For the Gulf of Mexico, curbing nitrogen runoff from farms can shrink the
dead zone. Applying fertilizer to match crop needs more precisely would
allow more nutrients to be taken up by plants instead of being washed out
to sea. Preventing erosion through conservation tillage and changing crop
rotations, along with wetland restoration and preservation, can also play
a part.

Innovative programs such as the American Farmland Trust's Nutrient Best
Management Practices Endorsement can reduce the common practice of using
too much fertilizer. Farmers who follow recommendations for fertilizer
application and cut their use are guaranteed financial coverage for
potential shortfalls in crop yields. They save money on fertilizer
purchases and are insured against losses. Under test programs in the
United States, fertilizer use has dropped by a quarter.

With carefully set goals and management, it is possible for some dead
zones to shrink in as little as a year. For other hypoxic areas
(especially in the Baltic, a largely enclosed sea with slower nutrient
turnover), improvement may take longer, pointing to the need for early
action. For while dead zones shrink or grow depending on nutrient input
and climatic conditions, the resulting fish dieoffs are not so easily
reversed.


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