The driving forces of wetland degradation in Bure and Wonberma Woredas, Upper Blue Nile basin, Ethiopia.

Abstract

Although the land use/land cover (LULC) of inland wetlands has been dynamic over the last 100 years, the extent of their LULC dynamics and its driving forces are poorly understood particularly in Ethiopia. Thus, this study analyzed spatiotemporal dynamics of four (Alefa, Chakun, Denbun, Kotilan) wetlands LULC and its driving forces in the Bure and Wonmbera Woredas, Upper Blue Nile Basin, Ethiopia for the period from 1985 to 2020. The Landsat images downloaded from Google Earth Engine were used to analyze the LULC of four wetland watersheds. These images were classified into 7 classes by using the maximum likelihood algorithm in ArcGIS 4. Besides, a survey of 347 households, 4 focus group discussions, and 12 key informant interviews and transect walks were used to generate the data on the drivers of wetland changes. The LULC analysis showed that the four wetlands area in 1985, 2002, and 2020 occupied 6027 ha, 5203 ha, and 4348 ha, respectively, which indicated that the areas of wetlands have declined by 1679 ha or 27.9% in the past 35 years, with an average annual decrease rate of 48.4 hectares. Wetlands were lost at a higher rate (16.4%) from 2002 to 2020. The cultivated land expansion has taken a substantial share (67.9%) of wetlands' decline. The expansion of cultivated land due to an increase of rural households along with a lack of alternative livelihoods resulted in the conversion of wetlands to cultivated land. Gully erosion and sediment deposits due to wetlands buffer degradation, overgrazing, and change in crop production driven by market opportunities have exacerbated the wetlands loss. Thus, interventions such as the promotion of alternative livelihood activities, stall livestock feeding or zero-grazing, and non-conventional livestock feeds are needed to curb wetland degradation. Delineation of buffer zone and protection of shrubland or woodlands found in buffer areas of the wetlands are needed as well for the sustainability of wetlands.