Impact of climate variability on vegetative cover in the Butana area of Sudan

Climate variability has an impact on the renewable natural resources. This impact is strong in regions with a delicate balance between climate and ecosystem, like the Sahelian regions. Rainfall is the most important climatic factor influencing livelihoods in Butana, north-eastern part of Sudan. All people and their livestock depend on the amount of rainfall that falls and supports plant growth. Butana area experienced severe drought in 1984, 1990 and 2000. Linear relationships between the long-term rainfall and AVHRR/NDVI data were developed for four separate zones in the Butana area. There is a significant correlation between peak NDVI (beginning of September) and cumulative rainfall for July and August, but weak relationships resulted when annual rainfall and cumulative NDVI were used. This is because the NDVI reached a plateau as the rainfall increased, then it remained constant despite further increases in rainfall. The departure from the long-term average of NDVI for each pixel was calculated using the departure average vegetation method. The area had a high percentage of departure during the drought years and the NDVI recovered during the following year when the rainfall was above the average. It can be noted that the area adjacent to the irrigated scheme showed considerable decrease in NDVI. This may be due to overexploitation by the nomads during the drought year.