For reptiles and other small vertebrates inhabiting the Coober Pedy opal fields of South Australia, daily life means having to watch where you step (or slither).
Approximately 2 million abandoned opal mine shafts, the legacy of exploratory drilling over the last 30 years, sit uncapped, ready to entrap the unknowing victim.
Reece Pedler with the South Australian Arid Lands Natural Resources Management Board set up an experiment to estimate the impact of these mine shafts on the fauna of the region.
According to the results, published in the journal Ecological Management and Restoration, uncapped opal mines in the area may be killing as many as 10-28 million reptiles per year or an equivalent of 25-72 tons of biomass.
To arrive at the figures buckets were wedged inside 43 opal mine shafts over the course of 13 months. Each bucket had a hole at the bottom and plastic jar under it which allowed the captured animals to avoid dessication or predation. The buckets were regularly checked for captured wildlife.
Based on the recorded captures, a total figure was calculated for the whole region with certain unknown factors accounting for the range of numbers. The broad-banded sand swimmer and the Bynoe's gecko were the most commonly captured species.
The mine shafts were also a problem for the nationally threatened bronzeback legless lizard. The reptile was only captured three times but that may translate into a much larger impact across the entire region.
The study did suffer from some shortcomings - specifically its small sample size and the fact that the sample was not random - sites were selected for ease of inspection.
Nonetheless, the findings are disconcerting and call attention to the need for action. Unfortunately, capping all the abandoned opal mine shafts in the area is unlikely anytime soon due to cost and logistics.
Therefore, "determining which shafts are the most effective traps may be an important tool in mitigating their future impact in a staged program." Reece writes, "The tops of existing uncapped shafts could be modified to create less effective traps while legislative changes may be used to ensure that future prospecting shafts present reduced danger to fauna."
--by Rob Goldstein
Reece D. Pedler (2010). The impacts of abandoned mining shafts: Fauna entrapment in opal prospecting shafts at Coober Pedy, South Australia Ecological Management & Restoration : 10.1111/j.1442-8903.2010.00511.x