Erosion Response to Landscape Unit Changes in Eastern Niger: The Case of Bagara and Issari

Abstract

Since the drought of the early 1970s, the Niger part of the Lake Chad Basin has undergone significant changes. Its environment has evolved considerably, with land cover and use (cultivation, grazing) experiencing significant momentum. This change in land use has led to a decrease in natural habitats (savannas and forests), thereby increasing the vulnerability of soils to erosion agents. Erosion dynamics (wind and water) have also undergone an evolution. The resulting erosive response to these changes was discussed and particular attention paid to the gully network dynamics and the Komadougou Yobe banks during the periods of 1957-1975 and 1975-2007. Three maps of gully dynamics were produced. Shreve order gullies remained constant and equal to two (2) between 1957 and 1975, going up to 4 in 2007. The gully network total length has evolved. From 1957 to 1975, it multiplied by four (4) and from 1975 to 2007 by three (3) or by nine (9) from 1957-2007. The two Komadougou meanders (B1 and B2) studied cartographically showed a strong momentum. Thus, at B1 and B2 level, a 120 m and 92 m bank recession was observed between 1975 and 2007 and the wavelengths have respectively increased from 196 m and 1083 m in 1957 to 349 m and 943 m in 2007. A tendency to overlap is thus observed at these meanders. If this degradation acceleration trend continues, we will witness a short term rural exodus, the abandonment of villages and competition on land that can lead to internal as well as extraterritorial conflicts.