Trends in Vegetation Response to Drought in Sudano-Sahelian Part of Northern Nigeria

Abstract

This\rstudy was carried out to evaluate the drought occurrence and its implication on\rvegetation cover over the Sudano-Sahelian zone of the Northern part of Nigeria.\rMonthly mean Rainfall data for the period 40 years (1971-2010) were obtained\rfrom Nigeria Meteorological Agency (NIMET) for each of the meteorological\rstations present and functioning in this region for climatic analysis.\rStandardized Precipitation Index (SPI) was used to analyze drought occurrence\ron a time scale of five (5) months that cover the period of raining season over\rthe study area. Also Satellite data over the selected part of the study area\rfor three different epochs, 1986, 2000 and 2005 were used for vegetation\rresponse analysis. The SPI values were interpolated using Inverse Distance\rWeighted (IDW) interpolation technique in ArcGIS 9.3 to generate Drought\rSpatial Pattern Map for each selected modeled years. The vegetation response\rindicators used are land cover maps and Greenness Index (GI) maps. Land cover\rcategories were classified into five levels: Dense Vegetation, less dense\rVegetation, Settlement/built up, Bare Surface and Water body. The results based\ron the ground truth (rainfall) data show that many years of drought episode\rwere experienced over the study area. On the other hand, the prime indicators\r(Land cover and GI maps) used in this study also depicts the changes that took\rplace over the study area in response to this climatic anomaly (drought) and it\rcould be noted that there was dramatic reduction in the occurrence towards the\rend of the last two decade, 1990-1999, which simply indicated improvement in\rrainfall even in 2000 and the later years.