The Bureau of Land Management (BLM) manages more than 260 million acres of public lands, mostly located in 11 western states and Alaska. Among the diverse natural and cultural resources under BLM's care are several hundred caves in the West. The challenge for BLM and other land managers is to protect fragile cave and karst environments and their valuable groundwater resources while also considering myriad other potential uses of these same areas, many of which are rich in resources such as timber, oil and gas, and other minerals.
By using a system of permits and gates, such as this one at Hot Springs Cave in Utah, BLM and other land managers can restrict access to caves that have valuable scientific or cultural resources or that pose dangers to the public.
ERIC KREUSCH, BLM
To unethical people, cave entrances such as this one in Warren, Kentucky, appear to be attractive places in which to dump trash. Because entrances also serve as recharge points for groundwater, this practice can quickly pollute local or regional water supplies.
Caves and their associated environments are very fragile ecosystems that are affected both directly and indirectly by human contact. Direct contact, in the form of exploration, recreation, and vandalism, can alter environments that have formed over millions of years. Human visitors can stir up dust and discolor speleothems, track in mud and leave boot marks, cause accidental or intentional breakage of speleothems, leave trash, and contaminate water sources. In addition, lighting, trail construction, building of nonnatural cave entrances, exhaled carbon dioxide, body oils, and noise from cave tours can all adversely affect the features and inhabitants of this underground world.
Less direct, but equally harmful, is damage from activities that take place above ground. Natural occurrences and human actions can cause numerous disruptions of the cave ecosystem. Timber harvesting, mining, grazing, farming, and urban development can all lead to the introduction of sediments into the cave/ karst system, as can natural wildland fires. Increased sedimentation can clog caves and crevices, alter drainage patterns, and change cave humidity and the pH of water in the cave. Alteration of airflow can also occur as a result of mining operations or the dumping of trash into sinkholes and cave entrances.
The intentional dumping of trash-from household garbage to abandoned cars to dead animals-is certainly an obvious source of cave pollution. But pollutants also enter cave/karst systems as a result of various other activities. Chemicals from mining operations; fertilizers and pesticides from farms; sewage; runoff from urban areas; and pollutants from timber slash and waste all can make their way into relatively closed cave ecosystems. The effects can be serious not only for the cave system but also for the quality of groundwater in the entire region.
Karst areas typically lack surface water and host numerous streambeds that are dry except in periods of high runoff. In these landscapes, with their absence of perennial surface streams, the entire region serves, in effect, as a recharge zone for aquifers. Water is rapidly conveyed to the subsurface zones of recharge through a network of fractures, partings, and cave entrances. In karst regions, groundwater is highly vulnerable to pollution because pollutants are only minimally filtered by typically thin soils, and are transported rapidly, both vertically and horizontally, to wells and springs.
Management actions can minimize these disturbances. Buffer zones can be created around cave entrances and sinkholes, and prohibitions on dumping enforced. In some cases, land managers can use permits to restrict recreational access to caves, either in terms of frequency of visits or size of visitor groups.
Caves can be closed temporarily during periods when bats are hibernating or roosting. And in situations where unique scientific or cultural resources are involved, land managers may need to deny access until the resources have been fully studied and secured.
Increased sedimentation associated with grazing, timber harvesting, mining, and wildland fire damage can be addressed through prompt reseeding and other soil stabilization efforts. Limits on construction and the careful siting of roads, pipelines, and rights-of-way can also be beneficial.
Land management decisions can also affect the quality of the water that enters caves and karst systems. In some areas, infiltration of grazing-related toxins into groundwater can be minimized by construction of fencing to keep cattle away from springs and waterways. Frequent relocation of livestock salt licks and watering tanks can also help by reducing soil compaction and the concentration of animal wastes.
Karst groundwater resources can also be protected by the careful siting of mining and other drilling operations; application of special drilling and well-casing techniques; and the use of special linings and berms to isolate any spills that may occur. The locations of landfills, underground storage tanks, oil and gas wells, and pipelines should be studied and carefully considered by land managers. Septic systems should not be placed near sinkholes, springs, caves, fractured bedrock, crevices, or in areas with thin soil cover. Minimizing the use of pollutants such as pesticides, fertilizers, de-icing salts, and petrochemicals should also be a management goal in these vulnerable areas. In regions where cave and karst resources are critical to municipal water supplies, or where cave and karst systems are particularly fragile, federal land managers even have the legal authority to close sensitive areas to mining, drilling, or other actions that could adversely affect the ecosystems and groundwater supplies.
A range of protective measures is available for implementation by federal land managers to varying degrees. But since many cave and karst resources are on privately owned lands, it is not always possible for federal managers to control vandalism and dumping. A great deal of what can be done to protect cave and karst resources is up to the public. Greater comprehension of potential problems and possible solutions, as well as more cooperation between the government and private sectors, is crucial.