http://story.news.yahoo.com/news?tmpl=story&u=/ap/20030813/ap_on_re_af/climate_warming_africa_1
Falling
Africa Fish Harvest Blamed on Warming
Wed Aug 13, 3:49 PM ET
By The Associated Press
Scientists are blaming
global warming for falling fish harvests
in Africa's Lake Tanganyika, threatening the diets of several
poor nations.
Warming air and water
and decreasing wind have reduced the amount
of mixing between the lake's surface water and deeper, nutrient-rich
layers. The changes have reduced algae growth, reducing food for
several important fish species, the researchers found.
Details of the lake
study appear in Thursday's issue of the
journal Nature.
Many scientists believe
that climate change is caused by large
volumes of carbon dioxide and other heat-trapping gases that
industrialized nations release into the atmosphere.
"This is an indication
of one area we haven't recognized
as a region that might be heavily impacted by the activities
of developed countries," said Catherine O'Reilly of Vassar
College, the study's lead author. "Other lakes might be
undergoing similar changes."
Lake Tanganyika is
the world's second largest lake,
containing 18 percent of the planet's liquid fresh water.
The lake yields 200,000
tons of fish a year, an important
source of food and revenue for the poor shoreline countries
of Burundi, Tanzania, Zimbabwe and the Democratic Republic
of the Congo.
However, the harvest
of sardines, the lake's main commercial
fish, has declined as much as 50 percent since the 1970s.
O'Reilly and others
from universities in the United States
and Belgium compared lake water temperatures, air temperatures
and wind velocities over the past 80 years.
Air temperatures over
the lake have increased by about 1 degree
Fahrenheit over the lake, while wind speeds have diminished,
they said. The temperature of deeper water has risen less
dramatically, resulting in less mixing of the layers, and
algae growth has dropped by 20 percent.
As temperatures increase,
the decline in the lake's productivity
is expected to continue, O'Reilly said.
Dirk Verschuren, a
biologist at Ghent University in Belgium,
wrote in an accompanying commentary that the study shows
global climate change has had a greater impact on Lake
Tanganyika than local human activity, such as farming.
