Quality of Mine Reclamation Vital for Bat Conservation

By Len Meier, Office of Surface Mining

Bat populations in the United States are declining. Of the 45 species present, six are either threatened or endangered, and 20 more are listed as species of special concern by the U.S. Fish and Wildlife Service. Reclamation of abandoned mines can have both positive and negative impacts on bat conservation. In November 2000, the Office of Surface Mining cooperated with state and tribal Abandoned Mine Land Programs, Bat Conservation International, and other government and local agencies in a National

 Forum on Bat Conservation and Mining to develop guidelines for helping preserve bat species.

This national forum focused on the relationship of abandoned mines to bats, the extent to which mine reclamation programs have contributed to bat conservation, and the scope of additional opportunities for bat conservation that are available to reclamation professionals.

Underground mines provide important habitat for many bat species. Sixty-two percent, or 28 of the 45 continental U.S. bat species, roost in mines. While for some species the use is only occasional, for most of the 28 species, mines constitute important roost areas. Underground mines provide both winter and summer roosting areas for bats. In the winter, many abandoned mines contain areas with constant, above-freezing temperatures necessary for hibernation. In the summer, underground mines may act as cold-sinks, similar to caves, protecting bats from extreme summer temperatures while providing shelter from predators.

Of more than 6,000 mines in Arizona, California, Colorado, and New Mexico surveyed for bat use prior to 1994, 30 to 70 percent showed signs of bat use, with an average of 10 percent containing important colonies. Twelve of the 16 species of bats found in Wyoming are known to use mines. For some western species, such as Townsend's big-eared bat and California leaf-nosed bat, the largest colonies now are found in man-made habitat. In the northern and eastern United States, bats may use up to 70 percent of open underground mines. Mines are known to be the most significant bat hibernation sites in Michigan.

Bats have been shown to use underground mines all across the U.S. for hibernation, day roosting, maternity shelter, feeding, and watering.

Closing mines can have both immediate and long-term impacts on bat populations. Historically, mine closing meant filling the mine entrance with solid fill or constructing a solid door over the opening.

Closing old mines during hibernation season, while bats are inside, can have disastrous results. A mine in Pennsylvania's Canoe Creek State Park was closed without regard to bat use but was reopened in time to save hibernating bats. The largest known hibernating population of bats in New Jersey was also trapped when the Hibernia mine was closed. Luckily, these bats were also rescued by the quick actions of biologists, who convinced authorities to reopen the mine. Many other bat populations have not been so lucky.

In preparation for the national forum, Homer Milford of the New Mexico Abandoned Mine Program and Len Meier of OSM surveyed state Abandoned Mine Land reclamation programs, wildlife agencies, federal reclamation programs, and local organizations to characterize the extent of reclamation opportunities that may effect bats, either positively or negatively, and to determine what reclamation programs have already accomplished to conserve bat populations.

The surveys concluded that there are more than 367,000 abandoned mine openings in the United States. This estimate is probably conservative because many of the survey respondents stated that detailed inventories are not available for their area.

According to survey respondents in 47 states and information contained in OSM's AMLIS system, over 32,000 mine openings have been closed by local, state, tribal, and federal agencies. (Table 1 summarizes the number of mine closures by state. Table 2 summarizes the number reported by Indian tribe.)

Survey results indicate that over 1,630 bat-friendly mine closures have been installed by state, federal, tribal, and local government agencies. Several respondents stated that bat gates were only installed when endangered species were suspected to use the opening. When non-endangered bats were the only users, mines were completely sealed. Other respondents said that bat gates were installed when any significant bat population was found. While tribal governments were not surveyed due to lack of time, available data indicated that at least five gates were installed on abandoned mines by tribal governments.

Open underground mines offer thousands of opportunities for bat use nationwide. The 367,000 open mines reported by respondents are scattered across 34 states from the Atlantic to the Pacific coasts. The majority of mine openings are in the western third of the nation, and nearly 80 percent are reported in just three states: Nevada, Arizona, and California.

Some openings provide winter hibernation sites because they exhibit the right combination of temperature, humidity, and airflow for bat survival. Many mines have been found to be critical hibernation sites for certain species. Closure of these mines without allowance for continued bat use could prove disastrous for entire species. Other mines are used as summer day or night roosts or for maternity habitat when young are most vulnerable. These mines may also be critical for the survival of specific populations or subspecies due to the loss of natural cave habitats to commercial development or other human activities.

On the other hand, many other mines receive only occasional use by bats and complete closure of these mines would not be expected to harm bats as long as none were trapped inside during the closure effort.

Government agencies have closed over 32,000 mine openings in 40 states and on 11 Indian tribal reservations (Table 2), and the rate of closures is increasing rapidly. According to AMLIS, 12,557 mine openings were closed between 1978 and 1994, reflecting an average annual rate of 785 openings. The average rate of mine closures between 1994 and 2000 was 2,000 per year, with the average going up to 2,813 openings annually in the last two years. With the rate of mine closures continuing to increase, the possibilities go up each year that critical habitats will be lost.

In recent years, more government agencies and offices have begun taking the needs of bats into consideration by surveying mines for bat use before closing them and by installing bat-friendly closures over the openings of mines found to be important bat habitat. Most mines are closed by government agencies for one of two reasons: either to exclude people for public safety reasons or to keep people out to protect important bat populations. In either case, closure methods must be permanent and vandal proof.

Bat-friendly closures are mine closure methods that allow bats to continue using a mine for hibernation, roosting, or other purposes important to the survival of the population. These include installation of vandal-resistant bat "gates," construction of structures that maintain appropriate airflow, and other measures that keep people out of mines but maintain current use by bats. About 1,639 of the mine closures reported by government agencies have been bat-friendly closures. This represents a mere 5 percent of all reported closures.

There are many reasons for this small percentage, including the following: mine openings are not occupied by bats due to physical and environmental conditions; mine closures involved mine subsidence openings that are only open for days or weeks; bat-friendly closures are only used when endangered species are known to inhabit the area; mines contained bat populations that were never discovered due to inadequacy or lack of bat surveys; and agency officials avoid bat-friendly methods due to concern over vandalism and long-term maintenance.

The first two reasons listed above represent quite legitimate situations for not using bat-friendly closures. However, the last three reasons represent missed opportunities that offer important ecological benefits from reclamation work with little additional cost. It is important that each mine reclamation program take a fresh look at the situations where they choose not to install bat-friendly closures and consider the costs of such missed opportunities.

It is unfortunate that some reclamation programs only install bat-friendly closures where endangered species are involved. With so many bat species declining due to habitat destruction by unregulated activities, failure to protect all bat populations that use mines proposed for reclamation adds unnecessary pressure to already declining species. When bat surveys are inadequate or conducted only in areas known to support endangered species, the risk of harming locally important bat populations increases.

These bats may perform many locally significant functions, such as pollination, insect control, and maintenance of the overall ecological balance. Loss of even these non-endangered bats can damage the delicate ecological balance in the project area. Finally, and most tragically, failure to use bat-friendly closures due to concern over reclamation methods, is not only the easiest situation to remedy but also probably the most common in many reclamation programs.

Concerns about permanence of closures are mainly based on failures of bat gates installed years ago or those that used old-technology materials and methods. Reclamation efforts funded by Interior and state Abandoned Mine Land Programs in New Mexico, Colorado, Utah, and Texas, as well as by Bat Conservation International, have developed high strength construction methods that resist vandalism better than past methods. Modern materials, combined with interagency agreements to monitor bat closures, significantly reduce the risk of people being injured by failed or vandalized mine closures.

The Office of Surface Mining is continuing to work with Bat Conservation International to improve technology for bat conservation practices and to make it available to all mine reclamation programs. For more information on OSM activities and support for bat conservation and mining, visit OSM's website at http://www.mcrcc.osmre.gov. or contact Len Meier at 618-463-6463, ext. 109 (e-mail lxmeier@osmre.gov.)

Bat Conservation International has recently updated their resource publication, Bats and Mines, which contains valuable information about bats and mines, including sample designs for bat-friendly mine closures. For more information or to get a copy of the publication, visit the group's website at www.batcon.org and click on the Mines Project tab under the Projects heading, or contact Sheryl Ducummon at Bat Conservation International, 512-327-9721; e-mail sducummon@batcon.org