|Implications of expected climate change in the Eastern African Coastal region: an overview|
Alusa, A.L.; Ogallo, L.J. (1992). Implications of expected climate change in the Eastern African Coastal region: an overview. Regional Seas Reports and Studies = Mers régionales Rapports et Etudes, 149. [S.n.]: Genève. 27 pp.
Part of: Regional Seas Reports and Studies = Mers régionales Rapports et Etudes. UNEP: Genève, more
Climate change; Environmental impact; Sea level changes; East Africa; Marine
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It is generally agreed that enhanced greenhouse effects and their associated impacts will result in severe changes to the climate and ecosystems of the region. There is however no definite indication as to the precise magnitude of the temperature and sea-level changes at a regional level. Models have estimated the average rise in mean global temperature and sea-level to be about 1°C and 20 cm respectively by the year 2030. With the assumed temperature changes it is expected that there will be changes in the characteristics of the monsoon winds which would lead to changes in precipitation patterns over parts of the Eastern African Region. However, it is expected that the many differences in topography, and other environmental parameters will lead to extreme variation in the changes of precipitation. Changes in temperature will further lead to changes in the evapotranspiration rates, with deleterious effects on crops in the drier areas where the water resources are generally limited. The need for a regional climate scenario is critical for an accurate forecast of the impacts of temperature increase and sea-level rise. Such a scenario would take cognizance of the varied topography and the existence of many island states within the region. Until then, the impacts will remain in the realm of educated guesses based on presumed scenarios which are themselves uncertain. Predicting the effect of temperature increases on agriculture is indeed very difficult. To the extent that if it leads to increased rainfall it can be said to be positive, but in the drier areas where droughts will persist and be more intense the effects will be negative. The demand for irrigation will increase and lead to possible stress on available water resources. Salination of irrigation water will affect the cropping patterns along the coastal areas which may necessitate a change in farming practices. The effects of sea-level rise appear much easier to forecast but no clear indication of the expected regional sea-level rise scenario has been developed. Assuming a sea-level rise of 20cm (local sea-level rise could be much more than this) the effects could be minimal but there will be impacts such as: (a) Wave-induced erosion and other impacts on exposed coasts, such as those to be found in island states, and on ports in the entire region. (b) Flooding of canals and estuaries, lagoons, etc., which have far-reaching implications for agriculture. The effects could be more serious if subsidence occurs which would mean higher relative sea-level rise. Not enough is known of the geology of the area to estimate these local effects with any accuracy. An increase in the intensity and frequency of tropical cyclones will have a devastating effect on the island states of the area. If they change their tracks, areas not hitherto used to dealing with tropical cyclones will be prone to extensive damage. None of the suppositions on the frequency or intensity of tropical cyclones however, has been methodically examined and any impacts cannot be specific to any one area at this time. There are likely to be impacts on industry in the coastal areas which will have socio-economic significance. Sea-level rise will affect the shipping industry and fishing while any increase or decrease in precipitation will influence the productivity of agro-based industry in the region. The expected negative impact of increased rainfall on road transport will further affect the movement of raw materials from up-country to the coastal areas hence influencing industrial productivity that may lead to unemployment and other socio-economic problems. Temperature increase and an increase in C 02 may have a positive impact on forest growth although in the drier areas the potential for forest fires will be greater. With increased precipitation, it is expected that there will be an increase in weeds and the warmer temperature will favor an increased risk of agricultural pests especially in swamps. As temperatures increase, ecosystems will migrate or adapt gradually, but it is likely that biodiversity will be reduced, especially on islands, due to the limited supply of fresh water. Gradual adaptation of ecosystems will however, depend on the rate, intensity and duration of the climate change.