Degradation of the riparian wetlands in the Lake Victoria basin - Yala swamp case study.

Land degradation is as a result of broad range of scales and factors, which include biophysical, climatic, demographic and socio-economic. The aim of this paper was to provide an analysis of wetland utilisation, ecosystem degradation and their effect on the Lake Victoria (Kenya) ecosystem. This involved analysis of socioeconomic and remote sensed data. The main sources of wetland degradation in the Lake Victoria basin were identified as (1) farming activities, (2) grazing and macrophyte harvesting and (3) coupled with catchment degradation-deforestation. These factors were closely related to the demographic dynamics and unsustainable land utilisation practices. Socio-economic data provided valuable insight on the pattern of wetland utilisation and possible sources of degradation pressure. For example, there is high dependence of the local indigenous livelihood directly on the swamp for subsistence needs including farming, grazing and income generation. Farming is the most important wetland utilisation activity, which takes 95% of the households wetland land holding mainly for subsistence use. In addition, there has been progressive degradation of the catchment area through deforestation, overgrazing and low furrow period. This results in high sediments transport and other pollutants to the lake ecosystem due to the removal of buffering effect of the macrophytes in the swamp especially along river Nzoia systems. Remote sensing data indicated progressive opening of the swamp especially in the high population and more accessible northern side of the swamp. In conclusion, the unsustainable use of natural resources in the basin has had significant negative effect on the Lake ecosystem including water pollution siltation and increase of floating biomass.

Published