Assessment on the Shrinkage and Ecological Importance of Wetlands of Fogera Plain, North West Ethiopia

Abstract

This study investigates the shrinkage, carbon sequestration potential and biodiversity richness of wetlands of Fogera plain, North West Ethiopia.  Landsat MSS of 1986, Landsat TM of 1994 and Landsat ETM+ 2011 were used to study the change in areas of wetlands over time. Supervised image classification through maximum likelihood classifier algorithm was used. Besides to this, interview and focused group discussion were used for the qualitative study of wetlands shrinkage. Soil sample were taken from three classes of wetlands i.e permanent wetlands (undisturbed wetlands), less disturbed wetlands and temporary wetlands. From each category of wetlands, 23 composite soil samples in three replications at a depth of 0-75 cm were collected. Sample soil organic carbon and organic matter were analyzed in soil laboratory.  The result of Landsat images analysis showed that the area of the wetland in Fogera plain is decreasing. It was 25% of the area in 1973, while it shrinked in to 19.59% in 2011. For this, sediment deposition, practice of unsustainable farming practices by local farmers and problem of land ownership are the major causes. There is a significant difference (p < 0.05) in soil OC and OM content in between different classes of wetlands. The organic carbon content of soils of permanent wetlands where there is sediment deposition is very low. In less disturbed wetlands, there is better carbon content than other state of wetlands. Totally, carbon sequestration potential of these wetlands is very low in comparison with the carbon content of the wetlands of other parts of the world. Because in these wetlands there is high deposition of sediment with high sand content transported from the upstream watersheds by Rib River.  This triggers the wetlands to lack their pristine nature.  The wetlands of Fogera plain are home for different species of birds and fish.  In these wetlands, 207 bird species during the wet and dry seasons were observed. The wetlands are rich in and nursery habitat for Labeobarbus and Clarias gariepinus fish species. This study recommends a call for wetland conservation and rehabilitation efforts through incorporating wetlands into watershed management plans, better community management system and effective land registration and certification program.

Key words: wetland shrinkage, carbon sequestration, sedimentation