Alteration of habitat following subsidence due to longwall mining was listed as a KEY THREATENING PROCESS on Schedule 3 of the Threatened Species Conservation Act 1995 [15 July 2005].
Longwall mining is an underground coal mining technique that involves removing a panel of coal. Longwall mining can cause the land above the mined-out coal to destabilise and collapse this is known as subsidence. Subsidence due to longwall mining has been recognised as causing habitat alteration, such as causing cracks beneath a stream or other water body. This may lead to a temporary or permanent loss of water flows and could cause permanent changes to riparian community structure and composition.
Species and ecological communities that depend on aquatic and semi-aquatic habitats are particularly susceptible to the impacts of subsidence. Subsidence can cause a decrease in water quality such as reduced oxygen availability, encouraging bacterial growth, smothering native plants and animals. Subsidence can also increase the amount of iron oxides in the water which directly affects native plants and animals.
Threatened species and ecological communities are known to occur in areas affected by subsidence due to longwall mining and include the following: Blue Mountains water skink, giant dragonfly, broad-headed snake, Epacris hamiltonii, eastern pygmy possum, giant burrowing frog, stuttering frog, and large-footed myotis, Genowlan Point Allocasuarina nana heathland, O'Hares Creek shale forest, shale/sandstone transition forest, and the Newnes Plateau shrub swamp in the Sydney Basin Bioregion.
Longwall mining occurs in the Northern, Southern and Western Coalfields of NSW. The Northern Coalfields are centred on the Newcastle-Hunter region. The Southern Coalfield lies principally beneath the Woronora, Nepean and Georges River catchments approximately 80-120 km SSW of Sydney. Coalmines in the Western Coalfield occur along the western margin of the Sydney Basin.
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