Ecosystem recovery analysis of mine tailings at Mhangura copper mine through normalised difference vegetation index

Abstract

Remote sensing techniques are increasingly being employed in monitoring environmental change. Vegetation indices such as normalised difference vegetation index (NDVI), are useful in estimating primary production, an important component of ecosystem function. The success of rehabilitation on mine tailings may be indirectly assessed through NDVI changes. Mine tailings at Mhangura copper mine, Zimbabwe, have not been monitored since their rehabilitation following the mine closure in 2000. The present study indirectly assesses primary productivity over the tailings dams as a way of establishing the extent of ecosystem recovery. NDVI images were obtained from the United States geological survey (USGS), global visualisation viewer (GloVis) website. These were processed using the Integrated Land and Water Information System (ILWIS) Version 3.3 GIS software. Two-way ANOVA showed significant differences in NDVI between the sites (p < 0.05). Actual NDVI trends over the years could not be established. NDVI values over the dams were also significantly different from those in adjacent natural Acacia woodland. These observations were supported by principal components and hierarchical cluster analyses. The NDVI analysis thus showed a good establishment of grass on the dams with poor tree cover when compared with the Acacia woodland. This suggests a positive movement towards recovery. However, factors preventing tree establishment need to be investigated.

Keywords: Ecosystem development, normalised difference vegetation index (NDVI), remote sensing, tailings rehabilitation.