Land-use cover change impact on Cranes nesting space in the Lake Tana Biosphere Reserve area, Blue Nile Basin

Abstract

Lake Tana is the largest lake in Ethiopia, and it is the origin of the Blue Nile River (Abay). It harbors winter birds and globally threatened bird species. The wetlands in the area are nesting places of Wattled and Black Crowned Cranes. The wetlands are being converted into different land uses; however, how much area of these wetlands is being converted into different land uses is not known yet. This study therefore investigated the land-use change of the main nesting place of cranes in Chimba and Yiganda wetlands, in the Lake Tana Biosphere Reserve area. The land-use cover change was estimated by analyzing satellite images (Landsat images-ETM + from USGS website) from 1986 to 2016. The result showed that in 1986, the Chimba wetland area covered a total of 15,134,974.6 m2, which is 7.4% of the total area of Chimba watershed (203,312,456.3 m2). Other land use land cover types in the study area namely cultivated land covered 31.9%; farm village 2.1%, natural forest 41.3% and grass land 17.3%. However, the land-use land cover change (LULC) in 2016 showed that the wetland coverage declined to 10,708,894 m2. About 27.6% of the wetland is converted completely into cultivated land. Yiganda watershed covered about 28,075,506 m2 in 1986 of which 5,351,641.7 m2 was wetland area; however, the wetland area has shrunk to 4,668,162.9 m2. When it is compared to the wetland change in 1986 to 2016, Chimba wetland was more affected in which 663.5 ha was changed into another land-use land cover; whereas in Yiganda it was about 137.2 ha changed during the last 30 years. When the exponential trend change of LULC is observed, it could affect crane ecology by reducing the habitat availability for cranes nesting spaces.