At least some are acting to reverse this trend.
Another reason to cut fossil fuel usage, increase sustainable organic
farming, vegetarianism, and encourage lower population growth.
I really have trouble understanding people who don't know the meaning
An idea--suburban dwellers should have enough chickens to supply their
own eggs and a vegetable garden instead of a lawn. The chickens can be
fed on kitchen scraps, which now are being ground up in the garbage
disposal for the ocean to deal with adding to the pollution of the
ocean, and produce (and pests) grown in the garden. Think of the
benefits from eating their own eggs and food from the garden. More
healthful, fresher vegetables, and probably cheaper. The environment
would benefit from less transportation resulting in less pollution and
less large scale fertilization (the suburbian can use the chicken
manure and compost anything the chickens don't eat).
June 16, 2004-10
Copyright © 2004 Earth Policy Institute
Dead Zones Increasing in World's Coastal Waters
As summer comes to the Gulf of Mexico, it brings with it each year a
"dead zone" devoid of fish and other aquatic life. Expanding over the
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
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
dissolved oxygen to sustain life. Since the 1960s, the number of dead
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
and seas they fertilize microscopic plant life as well. In the presence
excessive concentrations of nitrogen and phosphorus, phytoplankton and
algae can proliferate into massive blooms. When the phytoplankton die,
fall to the seafloor and are digested by microorganisms. This process
removes oxygen from the bottom water and creates low-oxygen, or hypoxic,
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
to large seabeds spanning some 70,000 square kilometers. Most occur in
temperate waters, concentrated off the east coast of the United States
in the seas of Europe. Others have appeared off the coasts of China,
Brazil, Australia, and New Zealand.
Coastal Dead Zones Around the World
Source: UNEP, GEO Yearbook 2003 (Nairobi: 2004), compiled from Boesch
Caddy 2000, Diaz et al. (in press), Green and Short 2003, Rabalais 2002.
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.
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
The one in the Gulf of Mexico, now the world's second largest, disrupts
highly productive fishery that provides some 18 percent of the U.S.
catch. Gulf shrimpers and fishers have had to move outside of the
area to find fish and shrimp. Landings of brown shrimp, the most
economically important seafood product from the Gulf, have fallen from
record high in 1990, with the annual lows corresponding to the highly
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
the Mississippi basin, more than triple the average flux measured
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
rise over the last half-century. (See data.) 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
capacity to filter nutrients has been reduced as wetlands are drained
as areas along riverbanks are developed. Over the last century, the
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
to restore ecosystem functions. Fortunately, there are a few successes
point to. The Kattegat straight between Denmark and Sweden had been
with hypoxic conditions, plankton blooms, and fish kills since the
In 1986, the Norway lobster fishery collapsed, leading the Danish
government to draw up an action plan. Since then, phosphorus levels in
water have been reduced by 80 percent, primarily by cutting emissions
wastewater treatment plants and industry. Combined with the
of coastal wetlands and reductions of fertilizer use by farmers, this
limited plankton growth and raised dissolved oxygen levels.
The dead zone on the northwestern shelf of the Black Sea peaked at
square kilometers in the 1980s. Largely because of the collapse of
centralized economies in the region, phosphorus applications were cut
percent and nitrogen use was halved in the Danube River watershed and
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
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
For the Gulf of Mexico, curbing nitrogen runoff from farms can shrink
dead zone. Applying fertilizer to match crop needs more precisely would
allow more nutrients to be taken up by plants instead of being washed
to sea. Preventing erosion through conservation tillage and changing
rotations, along with wetland restoration and preservation, can also
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
States, fertilizer use has dropped by a quarter.
With carefully set goals and management, it is possible for some dead
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.
Copyright © 2004 Earth Policy Institute