Assessment of degradation features and their development into the post-drought period in the west-central Sahel using Landsat MSS

Long-term rainfall trends have shown that although drought periods have recurred in the west-central Sahel since 1990, the frequency and duration has escalated since the 1960s. Data from vegetation sites along north-south transects indicated that aspects of degradation varied considerably throughout the study region. Visual mapping techniques using Landsat MSS data in conjunction with fieldwork facilitated assessment of degradation feature identification and relative browse thinning throughout the area, with the southernmost populated area being worst affected. Regional differences showed that hydrologically induced erosion features covered less extensive areas and were more prevalent in the east, while active sand movement covered > 10,000 km2 and was more prevalent in the west. Rate of change in the post-drought period showed areas subject to water erosion increasing (due to increased rainfall) while areas of windblown sand were becoming increasingly stabilized. In combining browse thinning with total degraded area, the western image areas of Ayorou, Gossi and Niafounké appeared to be the worst affected while the eastern areas showed less overall degradation.