Crude-Oil-Spill-Induced Spatial Variation in Woody Species Populations of an Oil-Rich Community in Rivers State, Nigeria

Abstract

We used the spatial analogue technique of studying ecosystem dynamics to evaluate the impact of crude oil pollution on species composition and populations of woody plants in an oil-producing community in Ogoniland located within the Niger Delta Region of Nigeria. Three sites – Unpolluted Site (US), Polluted/Treated Site (PTS) and Polluted/Untreated Site (PUS), were purposively selected for the study. Five 35m x 35m quadrats were randomly laid in each of the sites for woody species enumeration. Woody species diversity was measured using Shannon-Wiener diversity index (H'). Species richness was calculated using Margalef index (R); while similarity in species between sites was measured using Sorensen index (SI). A total of 2166 individuals belonging to 28 species and 16 families were recorded in US; 149 individuals belonging to 14 species and 11 families were recorded in PTS; while 72 individuals belonging to 7 species and 7 families were recorded in PUS. Species diversity was higher in US (H' = 2.917) than in PTS (H' = 2.406) and PUS (H' = 1.801). Species richness was also higher in US (R = 3.515) than in PTS (R = 2.598) and PUS (R = 1.403). Similarity in species composition was higher between US and PTS (SI = 0.48) than between US and PUS (SI = 0.34), and highest between PTS and PUS (SI = 0.67). The results showed that crude oil pollution has impacted negatively on woody species of the community. However, higher species richness and diversity in PTS than in PUS, and higher similarity in species composition between US and PTS than between US and PUS, underscores the relevance of proper remediation for the regeneration and restoration of the woody species of the area.