Effects of dust deposition from diamond mining on subarctic plant communities and barren‐ground caribou forage

Dust produced from mining has the potential to reduce plant cover, alter plant communities, and increase metal concentrations in vegetation—changes that may affect the amount, type, and quality of forage for barren‐ground caribou (Rangifer tarandus groenlandicus). We quantified dust deposition from Diavik Diamond Mine (Northwest Territories, Canada) and investigated the changes on forage quality, type, and quantity for caribou. From 2002 to 2016, dust deposition was measured, and vegetation cover and richness were assessed in permanent plots established adjacent to the mine and in reference areas 1–6 km from the mine. Lichen was collected from areas up to 100 km from the mine to determine metal concentrations. Dust deposition rapidly decreased within 4 km of the mine. Plant communities adjacent to the mine (within 500 m) had disproportionately increased cover of vascular plants and decreased bryophyte and lichen cover. Lichen sampled within 4 km from the mine had greater metal concentrations than those sampled farther afield. Concentrations of Al in lichen collected within 40 km of the mine exceeded safe exposure limits for consumption, assuming lichen comprised 100% of caribou diet. We conclude that dust deposition from mining is altering adjacent vegetation communities but that such changes to forage are unlikely to cause negative effects to caribou due to reduced lichen intake in summer and autumn, their migratory nature, and avoidance of mine‐influenced areas. However, minimization and reclamation of mine‐related disturbances will be important for maintaining sufficient quality forage and available habitat or space in caribou ranges. Core Ideas Dust deposition adjacent to the mine was 2–5 times greater than at 4 km distance from the mine. Dust deposition rapidly decreased within 4 km of the mine. Adjacent to the mine, vascular plant cover increased and nonvascular plant cover decreased. Lichen within 4 km of the mine had elevated metal concentrations vs. lichen 11 km from mine. Effects of dust within 4 km of the mine are unlikely to negatively affect caribou.