Invasive Species Compendium

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Abstract

Evaporative mine water controls on natural revegetation of placer gold mines, southern New Zealand.

Abstract

Surface and ground water runoff is controlled by impermeable substrates exposed by mining at two abandoned historic placer gold mines. The arid climate at these sites ensures that much of the mine water evaporates on these impermeable substrates to leave saline residues that include halite and bloedite encrustations up to 1 cm thick. Mine water compositions were reconstructed by leaching of the substrates. The dissolved load in the mine waters was derived primarily from marine aerosols in rainwater, with a minor component from water-rock interaction in the mines. Salination of the sites from mine water runoff has taken <100 years, and the saline soils have limited the colonisation of tall native and exotic plants. Instead, the mine soils now support a distinctive and rare inland salt-tolerant ecosystem with low-growing plants, and this natural rehabilitation has resulted in enhanced biodiversity for the area. Natural rehabilitation may be an appropriate management strategy for mines located in similar geological settings nearby, and elsewhere in the world.