Soil erosion threatens Lake Malawi's biodiversity
Monday, July 26, 1999
Blantyre, Malawi, Panafrican News Agency (PANA), by Raphael Tenthani
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 Bio-diversity Conservation Project in Africa's third largest lake, this body of water is a "treasure of bio-diversity and food basket of enormous 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 aquatic 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 communities 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 practice.
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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