'Dead zones' in world's oceans are growing, say alarmed UN scientists
There are nearly 150 dead zones across the globe, they are
increasing, and they pose as big a threat to fish stocks as
over-fishing, the United Nations Environment Program (Unep) said
in its Global Environment Outlook Year Book 2003, released at a
meeting of environment ministers in Korea.
These lifeless areas of the sea are caused by an excess of
nutrients, mainly nitrogen, that originate from heavy use of
agricultural fertilizers, from vehicle and factory emissions and
from human wastes.
They have doubled in number over the last decade, with some
extending over 70,000 square kilometers (27,000 square miles),
about the size of Ireland, Unep said.
Dead zones have long afflicted the Gulf of Mexico and Chesapeake
Bay off the East Coast of America but they are now spreading to
other bodies of water, such as the Baltic Sea, the Black Sea,
the Adriatic, the Gulf of Thailand and the Yellow Sea as other
regions develop, Unep said. They are also appearing off South
America, Japan, Australia and New Zealand.
The nutrient run-off from farm fertilisers, sewage and
industrial pollutants triggers blooms of microscopic algae known
as phytoplankton. As the algae die and rot, they consume oxygen,
suffocating all marine life.
"Humankind is engaged in a gigantic, global experiment as a
result of inefficient and often overuse of fertilisers, the
discharge of untreated sewage and the ever-rising emissions from
vehicles and factories," said Klaus Toepfer, Unep's executive
"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. Unless urgent action is taken to
tackle the sources of the problem, it is likely to escalate
Dead zones are especially dangerous to fisheries because they
afflict coastal waters where many fish spawn and spend most of
their lives before moving to deeper water, said Marion Cheatle,
Unep's senior environmental affairs officer. "It hasn't been
something well known by policy-makers," Ms Cheatle said. "But
it's been getting noticeably worse."
The economic costs associated with dead zones is unknown, but
predicted to be significant on a global scale. Unep is urging
nations to co-operate in reducing the amount of nitrogen
discharged into their coastal waters, by cutting back on
fertiliser use or by planting more forests and grasslands
along feeder rivers to soak up the excess nitrogen.