Ecological impacts of small-scale mining in the Dunkwa East municipality of Ghana

Abstract

Rehabilitation of mined land is crucial for ensuring improved livelihoods of communities in mining areas of developing countries like Ghana. The study assessed the impacts of small-scale mining on forest cover; concentration and distribution of soil nutrients and heavy metals. The vegetation data was obtained from 1000 (20 m × 20 m) plots and the soil samples collected from 120 (50 m × 50 m) plots. A total of 157 species (140 genera and 54 families) and 209 species (185 genera and 73 families) were identified in the mined and unmined areas respectively. Small-scale mining activities significantly (p< 0.05) reduced species diversity, and richness of species of higher conservation and economic values. Plant families, Euphorbiaceae, Rubiaceae and Asteraceae were the top-most contributors to species diversity while Asteraceae, Poaceae and Euphorbiaceae were dominant in both the unmined and mined areas. Species-wise, Pteridium aquilinum, Tridax procumbens and Waltheria indica in the unmined area and Chromolaena odorata, Sporobolus pyramidalis and Euphorbia hirta in the mined area were dominant. Nutrient (Ca, Mg, Na, N, P, K, and OC) concentrations and EC varied significantly (p < 0.05) between unmined and mined soils. There were no significant variations (p< 0.05) in the concentrations of heavy metals between both soils. Despite the generally poor (33.8%) soil quality in the study area, mining activities further reduced (24.2%) it. Soils from mined sites with unfilled /partially filled pits had higher levels of K, Mg and Na. As mined sites fallow period increased, concentrations of OC and Cd increased, while Ca, Mg, pH, Cu, Pb, As and value of EC decreased. The spatial patterns of Cu, As and Pb were generally dot-like in the unmined and mined areas, except Cd which had hot spots in Nyamebekyere. Mg, K and Na showed dot-like distribution in both areas, reducing further in the mined areas. Ca and P had patch-like distribution in both areas with higher levels in the unmined areas while N showed uniform patch-like distribution in both areas. Though educational attainment, religious beliefs and experience in mining significantly explained the opinions of small-scale miners on the effects of mining on the environment, the associations were not significant (Cramer`s V lessthan 0.3). The number of years that mined land remained fallow should be factored into the mined land rehabilitation processes. Plant species restoration is required in the mined area.