Maintain microclimate in closed/abandoned mines
Overall effectiveness category Unknown effectiveness (limited evidence)
Number of studies: 1
Background information and definitions
Closing mines and physically obstructing mine entrances can alter the internal microclimate and make conditions unsuitable for roosting bats. Adverse impacts on airflow and water drainage should be avoided. For a similar intervention, see ‘Restore and maintain microclimate in modified caves’. See also ‘Install and maintain cave gates to restrict public access’ for a study in which a stone wall and gate influenced the microclimate of a cave with an effect on hibernating bats.
Supporting evidence from individual studies
A before-and-after study in 2004–2007 at one mine in Southern Illinois, USA (Carter & Steffen 2010) found that modifying the microclimate within an abandoned mine by closing a human-made entrance resulted in an increase in the number of hibernating bats, including Indiana bats Myotis sodalis. Before the entrance was closed, <500 bats were counted hibernating in the mine and internal temperatures varied widely during the hibernation period (-2–18°C). After the entrance was closed, internal temperatures were more stable (11-13°C), and more bats hibernated within the mine (one year after: 1,500 bats; two years after: 2,500 bats). In summer 2005, a culvert with a door (1.2 m wide) was built into the horizontal human-made entrance shaft and the rest of the entrance was filled in. Three other entrances to the mine were left open. Hibernating bats were counted within the mine in 2004 before the entrance was closed, and in 2006 and 2007 after the entrance was closed.Study and other actions tested
Referenced paperCarter T.C. & Steffen B.J. (2010) Converting abandoned mines to suitable hibernacula for endangered Indiana bats. Pages 205-213 in: K.C. Vories, A.H. Caswell & T.M. Price (eds.) Protecting threatened bats at coal mines: A technical interactive forum. Department of Interior, Office of Surface Mining, Coal Research Center, Southern Illinois University, Carbondale.