Environment
Marine
Mapping and Monitoring
New atlas reveals seagrass loss and its impacts.
by Clifton Coles
he world's underwater meadows are deteriorating, threatening the manatees,
dugongs, turtles, and thousands of other animals and plants that depend on them, report
the authors of the World Atlas of Seagrasses.
Underwater grasses form a unique marine ecosystem that protects
fisheries and coral reefs and helps to prevent coastal erosion. An estimated 15% of
seagrass habitat has been destroyed by the side effects of construction in coastal zones,
boating, dredging, and land reclamation projects during the past decade.
These beds and meadows continue to be destroyed for short-term gain,
according to Mark Collins, director of the United Nations Environment Program's World
Conservation Monitoring Center. This destruction continues despite the value that intact
ecosystems bring to coastal societies through protection from the erosive impact of waves
and tides, habitat for fish and shellfish, and ecotourism attractions such as the dugong,
manatee, and green turtle.
In East Africa, for example, hotels remove dead seagrass leaves from
white sandy beaches frequented by tourists. Beached leaves release nutrients as they die
and decay, forming an important food for fish. Removing them accelerates beach erosion and
damages seagrass meadows on which fisheries and tourism rely, reports Caroline Ochieng of
Egerton University at Nakuru, Kenya, and London University's Wye College in Kent, England.
In contrast, a team from Kasetsart University in Thailand reports that
fishermen have been persuaded to change their harvesting technique, resulting in an
increase in the size of seagrass beds and bigger incomes from higher catches. More
extensive seagrasses have also helped the survival of the imperiled dugong, which has
become something of a national treasure and consequently a tourist draw.
Monitoring this important ecosystem is an indispensable aid to decision
makers and serves to help meet the target for reducing biodiversity loss agreed upon by
world leaders in Johannesburg in 2003, says Collins.
Source: United Nations Environment Program, World Conservation
Monitoring Center, 219 Huntingdon Road, Cambridge CB3 ODL, United Kingdom. Web site www.unep-wcmc.org.
