INFLUENCE OF CLIMATE VARIABILITY ON BIOMASS DENSITY OF SOUTH WEST NIGERIA: A CASE STUDY OF OYO AND OGUN STATES

Abstract

The study aims at examining the influence of climate variability on the biomass density of Oyo and Ogun States. Past records of rainfall and temperature data for the 1981 to 2010 covering the study area were acquired and used for climate variability analysis. The Normalized Difference Vegetation Index (NDVI) data from Advanced Very High Resolution Radiometer (AVHRR) (1981 -1999) and Moderate Resolution Imaging Spectroradiometer (MODIS) (2000 - 2010) satellites were employed for the Biomass analysis. These set of data were converted to grid points and extracted to statistical software for correlation and PCA (Principle Component Analysis).  The decadal analysis for each location revealed that Alabata recorded highest rainfall (103.21 mm) in 2000 and 98.285 mm in 1990, in 1980 and 1990 the same location recorded a temperature of 32.31 ⁰c with a slight decrease to 32.27 ⁰c in 2000. Biomass showed a steady decline from 0.68 (1980) to 0.67 (1990) and 0.46 (2000). Eggua recorded highest rainfall of 99.26 mm in 2000 followed by 1990 (91.63 mm) and the lowest in 1980 (76.013 mm). However, temperature was consistent for 1980 and 1990 (32.36 ⁰c). Biomass had a steady decline from 0.66 in 1980 to 0.64 in 1990 to 0.43 in 2000. Idode recorded 102.26 mm rainfall in 1980 and it increased to 104.115 mm in 2000 and in 1990 it decreased to 102.03 mm. Temperature ranges from 34.05 ⁰c in 1980 and 1990 to 31.77 ⁰c in 2000. NDVI decline in biomass across the decade from 0.64 in 1980 to 0.61 in 1990 to 0.33 in 2000. Irawo relatively had a low rainfall throughout the 3 epochs 1990 (94.36 mm) 2000 recorded 96.57 mm and 93.62 mm in 1980. Temperature was however consistent for 1980 and 1990 (31.91 ⁰c) with a slight decrease in 2000 to 31.79 ⁰c. Biomass was reduced for the 3 decades from 0.60 in 1980 to 0.57 in 1990 to 0.33 in 2000. Despite the general and consistent increases recorded in rainfall between 1980s and 2000s epochs, rainfall anomaly was consistently below normal for Eggua and Irawo in the decades 2000s. The study concludes that the continual increase in temperature has led to reduction in biomass of the study area.