Dynamics of Usangu plains wetlands: Use of remote sensing and GIS as management decision tools

Wetlands are resources of paramount importance with many values and functions that need proper management for their continued functioning and the delivery of benefits to the community. Sustained functioning of wetlands requires proper use of land and management of water. It is commonly said that increased human activities have had negative impacts on the Usangu Plains wetlands and that these wetlands are on the verge of total collapse due to altered flows. Nevertheless, these beliefs are little supported by quantitative data. A study on the dynamics of Usangu Plains wetlands therefore investigated long-term and seasonal changes that have occurred as a result of human and developmental activities in the study area for the periods between 1973 and 1984, and between 1984 and 2000. Landsat-MSS and Landsat-TM images were used to locate and quantify the changes. The study revealed a 14% increase in area covered by vegetated swamp between 1973 and 1984, and a decline by 77% and 70% in area covered by closed and open woodlands respectively. Between 1984 and 2000, the vegetated swamp cover declined by 67%, while the closed woodland and open woodlands declined by 83% and 77% respectively. It has also been revealed that the differences in spatial resolution could impair the detection of change. The continued decline in wetland covers has the potential to cause irreversible changes in these wetlands. Remote sensing and GIS technologies have proved to be useful tools for assisting decision-makers to locate and quantify changes in land resources, and hence to identify appropriate solutions for sustainable management of wetlands.