Lake Naivasha in Kenya in danger of extinction
Monday, December 16, 2002
The Nation (Nairobi, Kenya) Steven Njuguna
Lake Naivasha, a wetland of national and international importance, is under siege from human activities. If these activities are not controlled soon, the lake may cease to exist as a natural ecosystem in the next 20 years.
The lake is subjected to all kinds of adverse environmentally degrading activities including overfishing, introduction of alien invasive species, upstream diversion of water, abstraction of water for irrigation and geothermal power generation, wetland reclamation, clearance of papyrus vegetation, land-grabbing, agricultural and urban pollution, and catchment degradation.
On the basis of its unique and rich biodiversity, Lake Naivasha was designated Kenya's Second Ramsar Site under the Ramsar Convention on Wetlands in April 1995. The first lake to be so designated was Lake Nakuru in 1990.
Lake Naivasha is considered an outstanding wetland because of its unique and complex geological, biological, ecological and hydrological systems. It is of significant value in supporting diverse human communities dependent on the ecosystem.
The lake and its environs support a rich variety of wildlife - hippopotami, zebras, gazelles, impalas, elands, dik-diks, waterbucks and ostriches - and has thus become a major tourist attraction.
Decline in fish catches
The lake basin has been termed one of the world's finest aviaries. In addition to birdwatching and game viewing, other tourist activities in the lake basin include commercial fishing, sports fishing, water skiing and camping.
The fish population is based on introduced species. Originally, only one endemic species of fish, the small tooth carp was present. This species is now extinct. Four species, namely, the red large-clawed crayfish, the black tilapia, the red-eyed tilapia, and the black bass account for commercial fisheries.
The crayfish was introduced from its native place of origin in Louisiana, USA, in 1970, to diversify the lake's fisheries. In the mid-1980s, it had grown from the initial 300 individuals to millions of the species harvested and exported to France, Holland and Belgium. Today, an average of 50 tonnes of crayfish are harvested annually from the lake.
In the recent past, there has been a decline in both the fish catches and the size of fish landed. To check this trend, the government imposed a temporary ban on fishing in 2001. The depletion of the fish stocks was due to bad fishing practices and a decline in the lake's water level. The number of fishermen licensed by the Fisheries Department is normally about 100. However, much of the fishing is illegal. The fishermen use destructive methods including under-sized nets. They also fish in areas designated for breeding.
Present yields of fish in Naivasha are far below the predicted yields based on the lake's primary productivity. In 1992, the quantity of fish landed in Naivasha was 238 tonnes. In 1996, it had dropped to only 96 tonnes. A multidisciplinary research project by Kenya Marine and Fisheries Institute and the Fisheries Department is underway to establish the fish stocks and monitor their recovery.
One of the most serious threats to the lake ecosystem is the proliferation of invasive alien plant species that include the water fern (Salvinia molesta) and the water hyacinth (Eichhornia crassipes).
The water fern was first reported in Kenya in 1957 at Kitale. It was introduced as an ornamental plant to beautify ponds and pools. Its native country of origin is Brazil. It was first reported in Naivasha in 1962. By 1970, it had spread into shallow bays and lagoons all round the lake. The introduction of a beetle, Cyrtobagous salviniae, also a native of Brazil, has controlled the infestation of the water fern.
The water hyacinth has over the last decade invaded the habitat previously occupied by Salvinia and is expanding. The hyacinth is the world's worst aquatic weed. Its native place of origin is Venezuela in South America. Now found in 50 countries on five continents, the water hyacinth is a very fast growing plant doubling its population in only 12 days. By 1999, it had covered about 25 per cent of the water surface.
Floating mats of the water hyacinth reduce oxygen and light in the water, kill off the microscopic algae that are the basis of aquatic food webs, and result in fish kills. Balanced ecosystems that have taken thousands of years to evolve are destroyed in a matter of years. Two biological control agents in the form of beetles have been introduced into Lake Naivasha to control the water hyacinth. But they have failed to do so in Lake Victoria.
Resource of great national importance
Continuous monitoring of the physical, biological and socio-economic conditions of the lake and its catchment is essential. A moratorium on further expansion of the horticultural farms should be put in place to allow the lake to recover.
A Lake Naivasha Environment Fund should be established to be used in restoration of degraded areas of the lake ecosystem. Levies paid to the fund could come from the horticultural farms, the geothermal power plant, fishermen, tourists, tourist hotels, tourist camps, industries, the municipality and the Government.
The high biodiversity of Lake Naivasha basin represents a resource of great national and international importance. Its conservation will depend on the co-operative efforts of conservationists, researchers, administrators, investors, farmers, and local communities.
The most important resource calling for conservation in Naivasha is water itself. The conflicting demands for freshwater, as a commodity must be addressed urgently. Management interventions should respond to activities upstream of the lake, those in the immediate environs of the lake, as well as those within the lake ecosystem.
Prof Njuguna is an environmental consultant with SPARVS Agency Ltd.
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