Spatio-temporal changes in land cover in response to anthropogenic and hydrodynamic factors in Nyando wetland, Kenya

Abstract

In the last three decades, wetlands have received much attention worldwide due to their declining coverage and spatial distribution with more than 50% lost since the 1950s. Like other wetlands worldwide, Nyando Wetland, the second largest lacustrine wetland ecosystem on the Kenyan shores of Lake Victoria, is facing a major threat of degradation from both the fluctuations of Lake Victoria water levels and anthropogenic factors operating in its neighbourhoods. This study was conducted to determine how the spatial and temporal changes in land use/cover in response to anthropogenic and hydrodynamic factors such as land use, human population growth and lake level changes affected the area covered by the wetland between 1984 and 2010. Remote sensing, ground-truthing, socio-ecological tools such as questionnaires, focus group discussion protocols and data analysis tools such as Geographical Information System, logistic, simple and multiple regression models were used to achieve the objectives of the study. The Driver-Pressure-State-Impact-Response model was used as a framework for analysis. Results showed that there is an increasing trend for small-scale agriculture (+58 ha/yr) against a decreasing trend for water area (-29 ha/yr) and a reduction by 31% of the area of Nyando Wetland over the study period. Population growth was found to indirectly but significantly (SSAg p = 0.01, R2 = 0.89; RFTw p = 0.01, R2 = 0.80) influence the decline in wetland area through agricultural activities. The receding shoreline had a significant (p = 0.02, R2 = 0.89) influence on the spatial decline of the wetland. The study concludes that anthropogenic and hydrodynamic factors are significantly affecting the wetland and could compromise its ecological integrity. It is recommended that long-term health of the wetland should be contingent upon sound and effective ecotone zone planning and management. Thus integrated participatory and adaptive research should be conducted to stimulate quick responses and regenerative actions that could be used to restore and conserve the wetland ecosystem.