During the past 2 decades, it has become apparent that there are many animal species living within rock spaces deep underground, as well as in shallow unconfined aquifers associated with rivers. Subterranean fauna have persisted and diversified in their relatively buffered underground habitats for millions of years. They include aquatic animals living in the groundwater (stygofauna) and species living in subterranean airspaces in rock above the watertable (troglofauna).
Although subterranean fauna are found in many areas of Australia, no systematic national surveys have been done to fully understand their distribution. As with many invertebrate groups, our knowledge of the subterranean fauna is limited, in part because of the difficulty in accessing, sampling and studying subterranean environments, which can be hundreds of metres underground. Currently, only a small proportion of species have been formally described, and many new species are still being discovered (Smith G et al. 2012). Another challenge in understanding subterranean faunal diversity is that many species are hard to differentiate from each other and are only distinguishable through genetic analyses (Harrison et al. 2014).
However, greater levels of information have become available in association with mining operations in Western Australia and Queensland. A large number of surveys have been undertaken in many of the mining water monitoring bores across the Pilbara in Western Australia, and in Queensland, as part of the mandatory consideration of subterranean fauna in environmental impact assessments for mining developments.
Troglofauna and stygofauna are particularly diverse in the Pilbara region of Western Australia (Eberhard et al. 2005, Guzik et al. 2011), where more than 1000 species are estimated to occur (Halse & Pearson 2014, Halse et al. 2014). Almost all of the subterranean fauna residing in the Pilbara are invertebrates, many of which are short-range endemics whose entire distribution is restricted to a small area (less than 10 square kilometres for many species) (Halse & Pearson 2014).
The primary threats to subterranean fauna are activities associated with mining developments, including removal or disturbance of geological strata supporting faunal communities, and drawdown of the watertable following mine de-watering. Although these impacts are highly localised, they can deplete populations with very small ranges. In response, the configurations of some mining impact areas in the Pilbara have been altered to reduce the threat to short-range endemic subterranean fauna (EPA WA 2012).
Ongoing improvement of our knowledge of the distribution, diversity and taxonomy of subterranean fauna is critical for management. New analytical approaches to data, as well as taxonomic and genetic analyses, are required to better understand the number and variety of subterranean fauna species. Considerable effort is now being made to ensure that survey data are captured in publicly accessible databases to facilitate more widespread understanding and interpretation. Research into subterranean fauna and the ecosystems they reside in is an ongoing part of mining operations that informs threat abatement actions.