Sewerage And Fertilizers Are Killing The Seas
By John Vidal
The Guardian - UK
Last summer every sea creature across an area twice the
size of Wales
was asphyxiated by severely depleted oxygen levels in the Gulf of Mexico. The same phenomenon,
the marine equivalent of the ozone hole, happened off South America, China,
Japan, south-east Australia,
New Zealand, and up to 150 other places.
A United Nations agency warned yesterday that the number
of these "dead zones," caused mainly by the run-off of nitrogen fertilizers from intensive farming and sewerage from large
cities, had doubled in the past 15 years and was increasing all over the world.
In a new report, the UN environment program said that
150 sea areas were now regularly starved of oxygen and were becoming major threats to already declining fish stocks, including
those in Europe, where areas of the Baltic Sea were lifeless for several months, as were parts of the Irish Sea and the Adriatic.
The Black Sea - the largest
and oldest "dead zone" in the world - supported only a few bacteria to a depth of 150 meters.
"Humankind is engaged in a gigantic, global, experiment
as a result of the inefficient and often over-use of fertilizers, the discharge of untreated sewage and the ever rising emissions
from vehicles and factories," said Klaus Toepfer, the UN environment program (UNEP) director. "The nitrogen and phosphorous
from these sources are being discharged into rivers and the coastal environment or being deposited from the atmosphere, triggering
these alarming and sometimes irreversible effects."
Some of the dead zones are less than one square kilometer,
whereas others are up to 70,000 sq km. Many have been found near the outlets of big rivers such as the Mississippi and the Yangtze, which drain huge industrial areas. Most lie off countries which
heavily subsidize their agriculture.
"What is clear is that unless urgent action is taken to
tackle the sources of the problem, it is likely to escalate rapidly," he said.
"Dead zones are especially dangerous to fisheries because
they afflict coastal areas where many fish spawn and spend most of their lives before moving to deeper water," said UNEP officer
Marion Cheatle. "It is getting noticeably worse."
She advised countries, which often share water basins,
to co-operate in reducing nitrogen discharges by cutting fertilizer use or planting forests along rivers to soak up excess
nitrogen. The "creeping dead zones" have been noted since the 1970s but the speed of their growth has surprised scientists
who are only now beginning to understand their mechanism.
Robert Diaz, professor of marine science at Maryland University
and author of the marine section of the report, said dead zones were fast becoming a bigger threat to fish stocks than over-fishing.
He warned that global warming, with its likely increase
in rainfall, was likely to aggravate the problem, because it would increase significantly the discharge of polluted water
from rivers into oceans.
The report, launched in South Korea at a meeting of 150 of the world's environment ministers, ranked dead
zones as one of the top 20 threats to the global environment. Others included dust and sand storms, more frequent around the
world as land is degraded, and impending global water shortages.
More than one in three of the world's population is likely
to suffer chronic water shortages in the next few decades, according to the report, while more than 2.4 billion people lack
access to basic sanitation.
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