Deforestation Culprit for Lake Victoria's Killer Weed
11/5/99
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Title: Scientists find new culprit for lake's killer weed
Source: Reuters
Status: Copyright 1999, contact source for permission to reprint
Date: November 5, 1999
NAIROBI, Nov 5 (Reuters) - Deforestation could be largely responsible
for a killer weed threatening the ecosystem of Africa's largest lake,
researchers said on Friday.
They said scientists working on the shores of Lake Victoria in East
Africa accidentally discovered a nutrient which is feeding the water
hyacinth whose tentacles have suffocated much of the lake's aquatic
life.
``We noticed a dramatic plume of nitrogen and phosphorous-rich
sediments that are feeding the water hyacinth,'' said Pedro Sanchez,
director general of the Washington based International Center for
Research in Agroforestry (ICRAF).
``This is one of the major causes for Lake Victoria's environmental
demise.''
ICRAF officials told Reuters that the denuding of forest around the
lake meant rain could sweep topsoil containing the nutrients more
easily into the water.
Scientists had previously believed that the nutrients were the result
of runoff from farmland on the shores of the 42,000 square mile
(108,780 square kilometre) lake, the second largest freshwater lake
in the world.
The water hyacinth, an aggressive floating weed that has carpeted
large areas, has starved fish and plankton of oxygen and sunlight and
reduced the diversity of important aquatic plants, the scientists
said.
An oversupply of nutrients and untreated sewage has also killed large
numbers of fish and caused a sprouting of toxic algae blooms on the
lake.
The killer weed is having a major impact on human settlements.
The hyacinth has caused lake water to stagnate, creating breeding
grounds for malaria spreading mosquitos. Snails that host bilharzia,
a human parasite that attacks the liver, lungs and eyes, also live in
stagnant water.
The weed has hampered trade around the lake which, coupled with a
drastic loss of fishing, has severely affected the lives of the 30
million people who depend on the lake for employment.
ICRAF announced it will be working with regional governments to
tackle the problem.
``The solution is simple, inexpensive and targeted,'' said Sanchez.
``It mainly involves reintroducing trees in the riparian areas at the
mouths of the three rivers that are most to blame for carrying large
sediment deposits.''