LAKE NAKURU'S HUMAN OCCUPATION AND ITS IMPACTS ON THE ENVIRONMENT
Lake Nakuru occupies the lowest point in a catchment basin of 1,800 sq. km. Its water budget is balanced by evaporation and rain, in-flowing rivers, alkaline springs, and ground water recharge. During the last 100 years, the catchment basin has been transformed from a sparsely settled and heavily forested area teaming with wildlife (Percival, 1928) to one that is heavily settled, extensively cultivated, and urbanized.
The history of modern settlement is recent. The catchment was opened to settlement in 1889 with the arrival of the Kenya-Uganda Railway. Increased access to this part of the country led to settlement by European farmers. Ranches and large mixed farms sprung up in the area, and the town of Nakuru grew in size and stature to become a district headquarters and the agricultural capital of the Rift Valley. By 1948 the township supported a population of 14,000 persons.
These developments were not without consequences for wildlife. Loss of habitat, interference with migratory routes, and uncontrolled hunting led to the decimation and dispersal of several species of wildlife (Kutilek, 1974). By 1960 Black rhinos, Maasai giraffes, and Elands, to name a few species, were virtually eliminated from the area; a nucleus of Nakuru hartebeest were shot into extinction.
Independence in 1963 ushered in a second settlement thrust and further changes in land use. Settlement schemes initiated by the government in 1962 brought the first wave of small scale-farmers into the catchment basin in 1967. Settlement initially took place on existing, large-scale farms bought from European owners. As the number of settlements increased over the next decade - a result of government initiatives, the formation of land-buying companies, and illegal occupation by squatters - they rapidly encroached into forest reserves.
Between 1970 and 1986, more than 400 sq. km of forest and areas under natural vegetation were estimated to have been cleared for cultivation and settlement. Large holdings purchased from European owners were fragmented into smaller, individually owned parcels of land. The influx of peasant farmers continued into the 1980s and was finally stemmed by land scarcity and the unavailability of government funds for settlement schemes (Nakuru District Environmental Report, 1987).
This rural-rural migration brought about a sudden and unprecedented upsurge in the catchment's population. In one of the earliest settlements, population density increased from 124 persons per sq. km in 1969 to 915 persons per sq. km in 1987 (WOODEC, 1987). Elsewhere in the catchment, rural population densities were lower. However, they continue to rise, from 164 persons per sq. km in 1979 to a projected 375 persons per sq. km in 1996.
Estimates made from catchment maps of 1970 and 1986 (Figures 1 and 2 Note:Temporarily unavailable) reveal the extent of change in land use over that period. The maps show a decrease in the land under forest and natural vegetation from 47% of the catchment area to 26% of the area. Large-scale farms and ranches shrunk from 34% and 21% of the catchment area to 13% and 11%, respectively. Small-scale subsistence farms, which replaced these land-use types, grew from insignificant numbers to occupy over 35% of the area.
Nakuru Municipality, located within a kilometer of the lake's northern shore, has expanded in size from an area of 8.5 sq. km in 1970 to its present size of 73 sq. km. Nakuru's population grew from 47,151 persons in 1969 to 92,880 in 1979. This growth rate was maintained through the next decade largely as a result of rural-urban migration, natural increase, and industrial promotion. The current population of Nakuru is estimated at 360,000 and is growing at a rate of 10% per annum.
The changes in land use described thus far continue to have serious implications for the lake and its unique ecology. The clear felling of vast tracts of forests could have the immediate effect of causing a major loss of nutrients through the removal of the vegetation alone. Exposure of the ground surface and changes in surface run-off characteristics could have continued the export of nutrients and soils from the deforested areas for several years thereafter. Since Lake Nakuru lies at the sump of the catchment, it is the final repository of the sediment and nutrient loads carried by feeder rivers. Forest removal is now strictly regulated, but the loss of soil continues even in present-day plantation forests as a result of disturbances caused by road building and timber extraction.
The depletion of natural ground cover is also thought to have altered the hydrological regime of the catchment. This loss is manifested today by declines in the stable yields of bore holes. It has also resulted in diminished surface flow into Lake Nakuru (Kimani et al., 1992).
Soil erosion arising from poor agricultural practice has been a problem since the 1930s. In addition, toxic contamination of the environment from the use and misuse of agrochemicals has occurred. These two conditions are important environmental consequences of present-day agriculture. In general terms, the environmental effects of any land use increase with the intensity of use. No where in the catchment is land more intensively used than in the Nakuru Municipality. Like most industrial centers, Nakuru is a prodigious producer of waste. Liquid waste of domestic and industrial origin is treated in two sewage plants before being discharged into the lake.
Waste-handling facilities for both domestic and industrial waste have not kept pace with the rate of production, thereby posing the threat of accumulation in the environment. The hydrological and pollution effects on the lake from increasing volumes of urban run-off is also worrisome. Recent analyses of storm water, sewage, and lake sediment have revealed the presence of heavy metals and pesticide residues. Both categories of pollutants are known to produce acute and chronic toxicities in birds and mammals.
CONCLUSION
From the point of view of a field practitioner, the most pressing problems confronting Lake Nakuru are threats to its water balance and water quality arising from human activity in its catchment basin. Several technical prescriptions have been suggested to counter these threats; some are being put into practice. Solutions advocated include improvements in population planning and distribution, restoration of ground cover in the catchment, improvements in soil management practices, reduction in the use of agrochemicals, and improvements in the handling and disposal of urban and industrial waste. However, to achieve sustained success in these areas of endeavor, an enabling environment must prevail and a clear link established between development policy and conservation of the environment.
The quantum leap from acceptance of moral concepts such as "sustainable development" to the task of institutionalizing them and actively putting them into practice must be made. Ways to enforce and reinforce existing environmental policy and legislation must also be found.
Environmental issues cannot be tackled in isolation of the prevailing economic and social problems. Poverty, for example, is known to cause and compound environmental problems. The issues of equity, security and political stability must also be addressed. Unless and until they are, sustainable development may not occur for many more years to come.
