Sensitivity Of Kenyan Ecosystems To Acidic Deposition: Validation Of The 1996 SEI Map

Abstract

Kenya is a land of contrasts, having a variety of ecological and climatic zones, and many soil types of different characteristics and composition. In view of the adequate data available, the sensitivity of Kenyan ecosystems to acidic deposition needs to be reviewed and vulnerable areas properly delineated. The 1996 SEI map therefore needs to be re-assessed. Where land use is the most important activity, consideration needs to be made of socio-economic and demographic factors when creating boundaries. Reduction in the already staggering soil fertility and an imbalance in soil mineral composition and organic matter could bring about negative changes in crop yields. Consequently insufficient food supply, poor incentives, unemployment, decreased foreign exchange earnings and a search for areas with richer soils will ensue. The overall effects will be population shifts and accelerated deforestation and soil degradation. We consider this to be the greatest problem that would be caused by acidic deposition in Kenya. Geological influences on land use are important since soil type, soil pH and to some extent C.E.C. depend on the underlying parent rock. The present map might be altered if geology is considered as a factor. Data needs to be analysed at regional level (or on a district basis) to aid validation of the map. This will further refine the boundaries of sensitivity classes, especially if emphasis is placed on soil type, soil buffering ability and base saturation. Regular monitoring of possible sources of acidic gas emissions, if undertaken, should take into account wind speed, wind direction and wind strength in addition to rainfall regimes and average humidity in each study area. In Kenya, sulphur dioxide emissions by some industries might in the near future be a great threat to a variety of ecosystems.