Kenya // The Rift Valley //

The thorns of the rose

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Despite the listing of Lake Naivasha as a Ramsar wetland site of global ecological importance in 1995, the future of the lake’s delicate ecosystem is far from secure. Naivasha’s multimillion-dollar horticultural industry is one cause for concern, particularly the use of pesticides on the lakeshore’s huge farms and the enormous volumes of water used to irrigate them.

It is becoming increasingly apparent, however, that the survival of the lake and its wildlife depends on a multitude of other factors ultimately linked to the country’s growing population. Since 1977 the number of people living near the lake has risen at least fivefold, and human waste has become a major problem due to inadequate sewage treatment facilities, with the result that some partially treated effluent is finding its way into the lake. The Malewa and Gilgil rivers (which flow into Lake Naivasha from the north) have also been dammed, rendering the lake even more vulnerable.

Consequently, the lake’s wildlife is seriously threatened. Until the exceptional 1997/98 rains raised the lake’s level, thereby diluting the pollutants, the fish eagle had been especially badly affected, though its numbers now appear to be stable. The birds were not getting enough to eat, and Louisiana crayfish, introduced in the 1970s for commercial fishing, were largely to blame. By eating their way through the lake’s flora (which, as well as acting as a soak for excess nutrients and a sediment trap, serves as food and cover for some species of fish and birds), the crayfish caused the water to become murkier, making hunting harder for the eagles. Fishermen also complain that tilapia and black bass have sharply declined due to agrochemicals washed into the lake, and many of the area’s 350 species of birds, as well as the hippos and other wildlife, are still in danger: the lily-trotter, the great crested grebe and the crested helmet shrike have already all but disappeared.

Some companies finally appear to be waking up to their responsibilities. Oserian, the huge Dutch-owned flower exporter, has developed a new way of fighting fungal diseases without resorting to chemicals, using geothermal steam to purge diseases in its greenhouses, while other companies have adopted computerized drip-irrigation to optimize their water efficiency.

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