Abstract:
This study evaluated the vegetation response to drought over the Sudano-Sahelian zone part of
Nigeria and the specific objectives are to assess drought occurrence, map the vegetation response
to this occurrence, investigate the spatio-temporal land cover change and develop drought spatial
pattern maps for the study area. Monthly mean Rainfall data for the period of 40 years (1971-2010)
were obtained from Nigeria Meteorological Agency (NIMET) for each of the meteorological
stations present and functioning in this region for climatic analysis. Standardized Precipitation
Index (SPI) was used to analyze drought occurrence on a time scale of five (5) months that cover
the period of raining season over the study area. Also Satellite data obtained from United States
Geological Surveys Archive over the selected part of the study area for three different epochs,
1986, 2000 and 2005 were used for vegetation response analysis. The SPI values were interpolated
using Inverse Distance Weighted (IDW) interpolation technique in ArcGIS 9.3 to generate
Drought Spatial Pattern Map (DSPM) for each selected modeled years. The vegetation response
indicators used are land cover maps and Greenness Index (GI) maps. The results of SPI analysis
revealed that many years of drought episode was recorded over the study area in the 1970s and
1980s but later reversed in the 90s towards the 21st century as the result show there was drastic
reduction in the occurrence which indicate improvement in rainfall. On the other hand, the
vegetation response analysis also depicted that the year 1986 was a dry year over the study area as
the spatial extent cover by the vegetation was much less compared to the bare surface. But in the
1990s, greenness has returned to the areas that were previously bare soil, an indication of
improvement in rainfall amount over the area. The study therefore concluded that there exists a
kind of inverse relationship between drought intensity and vegetation growth and time lag in their
response to dry or wet condition.
