In 'Dead Zones'
Starving The World's Seas
Zones', Where Pollution Has Starved The Sea Of
Life-Giving Oxygen, Are Increasing At A Devastating
Andrew Buncombe and Geoffrey Lean, May 15, 2005
arrived early; it's bigger than ever and it promises a summer
of death and destruction. The annual "dead zone" in
the Gulf of Mexico - starved of oxygen, and thus killing fish
and underwater vegetation - has appeared earlier than usual
is just one sign of a rapidly growing crisis. The number of
similar dead zones in the world's seas has doubled every decade
since 1960, as a result of increasing pollution. The United
Nations Environment Programme says that there are now 146 of
them worldwide, mainly around the coasts of rich countries.
Its executive director, Klaus Töpfer, calls their growth
"a gigantic, global experiment ... triggering alarming,
and sometimes irreversible, effects".
of Mexico dead zone - which can cover more than 7,000 square
miles - is mainly caused by fertilisers, flowing down rivers
to the sea. Every year the Mississippi river - which drains
41 per cent of the United States - dumps 1.6 million tons of
nitrogen in the gulf, three times as much as 40 years ago. Most
comes from the highly productive corn belt, which helps to feed
the world. The nutrients feed blooms of algae and phytoplankton.
The algae drain oxygen from the water, as do the decomposing
bodies of the plankton, when they fall to the seabed and die.
a fishery that provides one-fifth of the country's entire harvest
from the sea. As a result, catches of brown shrimp, the gulf's
most important species, have dropped since 1990. The worst years
match those with biggest dead zones, which appear to block juveniles
from reaching their offshore spawning grounds. Last year, the
dead zone was even blamed for a tripling in shark attacks on
Texas bathers. Fish and swimming crabs flee the pollution for
cleaner water, followed by the sharks.
recently found 19 locations with severely depleted oxygen in
the gulf, where they expected to find none at this time of year.
"It usually doesn't start until June," said Steven
DiMarco, a researcher at Texas A&M University, one of several
groups involved in the testing. "It was larger at that
time than it was at any time in 2004. During January and February
of this year, the flow of the Mississippi river was larger than
at any time in 2004."
levels between the fresh river water and heavier salt water
of the sea created the dead zone, which usually is at its most
severe between 30 and 60 feet below the surface. The zone was
first recorded in the early 1970s. It originally occurred every
two to three years, but now returns each summer.
biggest dead zone is in the Baltic, where sewage and nitrogen
fallout from burning fossil fuels combine with fertilisers to
over-enrich the sea. Fish farming can also exacerbate the problem.
a third of the world's dead zones are off the United States
- including a notorious one in Chesapeake Bay - but they also
cluster round the coasts of Europe and Japan, and have reached
China, Brazil, Australia and New Zealand.
fertiliser use has soared tenfold over the past 50 years, mirroring
the increase in dead zones. And half the natural wetlands that
used to filter out nutrients before they reach the sea have
been destroyed worldwide. Big farming states such as Ohio, Indiana,
Illinois and Iowa have drained more than 80 per cent of theirs.
is some good news. After the lobster fishery collapsed in the
Kattegat Strait between Denmark and Sweden 20 years ago, the
Danish government implemented an action plan, which dramatically
cut pollution from agriculture, industry and sewage and restored
experimental programmes in the United States - which persuade
farmers to use less fertiliser in exchange for a guarantee of
compensation if their yields drop - have cut its use by a quarter.
They raise the hope that, if expanded, the relentless growth
of the dead zone in the Gulf of Mexico might finally be reversed.