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dam-l Soil erosion threatens Lake Malawi/LS



Soil Erosion Threatens Lake Malawi's Biodiversity

July 26, 1999

Raphael Tenthani, PANA Correspondent

BLANTYRE, Malawi (PANA) - Researchers have warned that soil erosion is
threatening the viability of Lake Malawi, home to about 700
species of fish.

According to fish researcher Anthony Ribbink, who is managing a Southern
Africa Development Community and Global Environmental
Facility's Lake Malawi/Nyassa Biodiversity Conservation Project in Africa's
third largest lake, this body of water is a ''treasure of
biodiversity and food basket of ernomous value.''

Funded by donors, including the UNDP, FAO and DANIDA, the project primarily
focuses on fish conservation.

''Erosion is the most obvious cause for concern. It is carrying fertile
topsoil off the lands into the lake. Plumes of sediment get carried out
into the lake causing huge umbrellas of shade under which primary
productivity ceases,'' Ribbink warns.

He says the fish in the lake are being threatened because, after settling
on the lake bedrock, the plumes of sediment covers the algae and
other food sources of the fish.

''The sediment too has a negative impact on the fish which have to enter
the rivers to spawn,'' he adds.

Ribbink explains that it is important to keep the soil on the land to both
maintain and improve acquatic productivity and to save certain
species of fish.

He says there are indications of changes taking place in the lake in terms
of nutritious, non-toxic algae diatoms being replaced with less
nutritious and more toxic forms of fish food.

''There are also indications of a build up contaminants in fish, such as
mercury and DDT'' due to farming up land, he adds.

Ribbink nonetheless says the water and fish of the lake are generally
remarkably good but still a sensible approach should be devised to
keep them at that.

The rich biodiversity of the lake, shared by Tanzania and Mozambique, is
most apparent in the fish which represent 14 percent of the
world's fresh water fish and about 4 percent of all fish in oceans,
estuaries and fresh waters in the world.

In the project, Ribbink's team has mounted environmental education and
community awareness programmes to take messages to 100,000
people in surrounding communities through theatre and other media.

''The real challenge for the donor community is to ensure that the benefits
of conservation outweigh the costs and the communites realise
these benefits,'' he says.

Generally, concern has also been expressed over the decreasing number of
fish stocks in lakes, rivers and ponds because of an increase in
the number of fishermen using intensive methods that scoop up young fish
without regard to laws against this pracitce.

The fishermen's prime target in the last 10 years is the tasty tilapia
species, chief among them being the legendary Malawi delicacy locally
known as the ''chambo.''

Another fish researcher, Dennis Tweddle, also says the previously
sought-after ''ntchila'' fish, which in the 1950s was the major
commercial species of value in Malawi, is threatened with extinction.

For instance in 1991, Lake Malombe yielded under 500 tonnes of chambo
compared with an average annual yield in the early 1980s of
about 5,000 tonnes.

Fish, an important source of protein to 70 percent of the country's people,
has dropped from 14.7 kg per capita in 1970 to less than 7.0 kg
per capita in 1990.

Annual fish output for Malawi, according to fisheries authorities, is about
75,000 tonnes of which 83 percent comes from Lakes Malawi,
Malombe, Chilwa and Chiuta. The rest is from rivers and artificial ponds
and dams.

The growing number of fishermen - 30,000 according to the National
Statistics Office - has also put pressure on the stocks.

Legislation bans the catching of fish until they reach breeding age.
Although most fishermen are aware of this, they say large fish are rare
these days and they need the money to survive.

''Yes, we can wait for the fish to grow, but what do we do today? Where
will the money come from to buy food?'' is a typical argument
by the fishermen.

This attitude is exacerbated by the lax attitude in enforcing the laws by
the authorities who, in turn, claim the lack of enough manpower to
carry out the assignment.


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      Lori Pottinger, Director, Southern Africa Program,
        and Editor, World Rivers Review
           International Rivers Network
              1847 Berkeley Way, Berkeley, California 94703, USA
                  Tel. (510) 848 1155   Fax (510) 848 1008
                        http://www.irn.org
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