Paris: Lake Tanganyika, the second oldest
and second deepest lake in the world, is now at its warmest in
1,500 years, threatening the fishing industry on which
millions of lives depend, scientists said today.
The evidence comes from cores drilled into sedimentary
layers in the lake bottom that point to climate changes over
Tanganyika`s surface waters, at 26 degrees Celsius,
are now at temperatures that are "unprecedented since AD 500,"
they reported in the journal Nature Geoscience.
The warming accelerated in the late 20th century,
tallying with abundant data from other sites pointing the
finger at man-made, heat-trapping greenhouse gases, they said.
As it has warmed, the lake has also suffered a fall in
biological activity, they said.
Surface layers that warm become harder to penetrate by
cool currents, welling up from the lake`s depths, which bring
vital nutrients that feed the first links in the food chain.
Ultimately, commercial fish species become affected.
"The people throughout south-central Africa depend on
the fish from Lake Tanganyika as a crucial source of protein,"
said Andrew Cohen, a professor of geological sciences at the
University of Arizona, who took part in coring expeditions in
2001 and 2004.
"This resource is likely threatened by the lake`s
unprecedented warming since the late 19th century and the
associated loss of lake productivity."
An estimated 10 million people in Burundi, Tanzania,
Zambia and the Democratic Republic of Congo depend on the
lake, using it for drinking water and for fish, of which up to
200,000 tonnes, mainly sardines, are harvested each year.
The paper, led by Jessica Tierney, a geologist at
Brown University, appears in the journal Nature Geoscience.
In a separate study, a pair of Swiss scientists spelt
out detailed warnings about the peril facing Europe`s
Mediterranean rim from global warming.
Previous work has already established the Iberian
peninsular and European countries on the Mediterranean as
badly exposed to heatwaves and water stress, based on current