Using Orthoptera and Hymenoptera indicator groups as evidence of degradation in a mining concession (Tarkwa gold mine) in Ghana

Abstract

One of the most important bioindicators of change in habitat conditions, especially in tropical Africa, is change in insect diversity. In line with that, the dynamics of Orthoptera and Hymenoptera insect orders were studied and used as evidence of change in ecosystem health after a similar study on Lepidopteran groups revealed some level of degradation in the Tarkwa Gold Mine (TGM). Orthopteran and Hymenopteran species assemblages were sampled within the mine and characterised based on family diversity. Transect counts, sweep netting, malaise trapping and flight interception trapping methods were employed to sample abundance and diversity of insect assemblages of the above-mentioned insect orders. Results showed that few species belonging to these two orders were recorded within the mine, although the records were dominated by more aggressive and habitat degradation tolerant members as reported for the Lepidopteran group in a previous study. We conclude that records of diversity of these insect orders in this study shows a reduction in the ecosystem health within TGM. This finding is further proof that there is a general decline in biodiversity within the concession and hence care must be taken to encourage environmentally-friendly mining practices to avoid further degradation. Recommendations are made for environmental management to maintain more natural vegetation to serve as refugia for impacted animals within the concession.