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Abstract:
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Deforestation and agricultural production in the drainage basin of Lake Malawi have the potential to cause water quality deterioration that could impact the lake’s rich biodiversity. Runoff from agricultural lands may increase loadings of suspended solids and nutrients to the lake, and rises in lake levels may be caused by reductions in interception and evapotranspiration when forests are converted to cropland.
Forests intercept a large proportion of the rainfall, much of which is lost to the atmosphere through evapotranspiration. Forests transpire more water than crops, and these processes thus reduce surface run-off in forest environments.
According to Malawi’s National Environmental Action Plan (NEAP) of 1994, rapid expansion of agricultural production from the mid-1970s to late 1980s resulted in extensive deforestation.
(a) The rate of deforestation was 3.5% per annum during that period,
(b) it declined to 1.6% by 1994 because little forested land was left.
(c) Additional deforestation was caused by use of wood fuel for tobacco curing, cooking, and domestic heating.
Deforestation in the drainage basin of Lake Malawi may be similar to the national picture presented by the NEAP because the basin covers more than half of the country’s total area.
The authors of this document conclude that because of differences in spatial resolutions, AVHRR and MODIS sensors gave different values for areal extent of the forest, cropland and SSW land classes over the period of analysis. The extent of surface water remained virtually unchanged over the period 1982 - 2005. Both the AVHRR and the MODIS data show that crop-land was mainly derived from SSW. |