Assessing the Correlation between Forest Degradation and Climate Variability in the Oluwa Forest Reserve, Ondo State, Nigeria

摘要

Between 1981 and 1994, Nigeria lost 3.7 million hectares of its forests. It is estimated that less than 4% of Nigeria’s rainforest cover is left. Reckless use and abuse of the forest reserves in Nigeria lead to degradation. However, the relationship between forest degradation and climate variability has not been clearly elucidated. This study assesses the trend of forest degradation between 1986, 2002 and 2014 in the study area and also examines the correlation between forest degradation and climate variability using temperature and rainfall parameters. Classification of Landsat images (TM 1986, ETM+ 2002, and OLI 2014) and change analysis using NDVI values of three-timed period were performed to observe forest degradation in the study area. NDVI values were calculated by combining bands 4 (near infrared) and 3 (visible red) for Landsat TM and ETM+ and bands 5 (near infrared) and 4 (visible red) for Landsat OLI using the spatial analysis extension in ArcGIS environment Linear regression statistical analysis was employed to determine the correlation between forest degradation and climate variability. The results show a fluctuation in the trend of forest degradation, while a positive correlation coefficient of 0.58 shows that there is a relationship between forest degradation and temperature and rainfall variability. The study concludes that though there is a positive correlation between forest degradation and climate variability in the study area, the relationship is weak and not strong enough to make generalizations.