In other sections of this knowledge center you have learned that caves and karst harbor rare cave animals, irreplaceable artifacts and fossils, unique speleothems, and important water resources. Many enchanting caves and karstic areas are protected within the national park system, without proper management, however, the use of caves by humans can cause serious negative impacts upon cave and karst resources. A recent landmark decision, the Lechuguilla Cave Protection Act (P. L. 103-169, December 2, 1993), has helped the National Park Service manage caves properly. The passage of this act occurred after Lechuguilla Cave in Carlsbad Caverns National Park, New Mexico, was threatened by oil and gas exploration on adjacent Bureau of Land Management lands. The act states that "Lechuguilla Cave... [has] internationally significant scientific, environmental, and other values and should be...protected...against...adverse effects of mineral exploration and development." The act withdraws all federal lands inside the boundaries of a protected cave area from all forms of mineral and geothermal leasing. The protected area along the northern boundary of Carlsbad Caverns National Park was established by an expert panel of geologists and speleologists assembled by the National Park Service.
Human impacts can cause alterations in surface water flow patterns, alterations in or pollution of water infiltration routes, changes in cave airflow patterns, drastic modifications to cave microclimates, the introduction of foreign and harmful elements into caves, and the disturbance of cave biota. Biological resources already in jeopardy include several species of endangered bats, ferns, and lichens (Department of the Interior 1994).
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Caves and karst were formed and are continually being changed by a combination of geologic processes, such as dissolution, groundwater flow, and rock collapse. Interference with these processes changes the fundamental characteristics of the cave environment, often resulting in species endangerment and destruction of cave resources. Some of the major issues are:
Improper development in caves has led to the destruction of cave resources. Expanded entrances, elevator shafts, and gates have interfered with airflow patterns and animal movements. Gates that inhibit the daily passage of bats into and out of caves often result in bats abandoning caves altogether. Because of inappropriate construction and development, available habitat has been reduced and more than 50% of the bat species in the United States are in significant decline or endangered.
Urbanization is creeping up on many national park system units, including those with cave resources. Water, which is the building force of most caves, carves cave passages and sculpts unique speleothems. Cave species organize their existence around these water sources and depend upon them for their survival. Increased human activity, such as agriculture and road network expansion, threatens the quality and the quantity of the water that feeds and sustains cave systems. Excessive contamination may result from landfills and toxic waste dumps, sewage lagoons and septic tanks, underground gasoline storage tanks, oil and gas wells, and toxic chemical spills. All of these things can have bad effects on caves, cave life, and your life through the water you drink!
Unregulated or illegal access to caves has resulted in the destruction of cave resources. Vandals steal or deface unique cave formations and archaeological specimens. In addition, recreational visitors inadvertently import exotic species (e.g., spores, fungi), which affects the integrity of the biotic cave web; also oils, dust, and lint brought in by human visitors build up on speleothems affecting the survival of cave species and speleothem formation.
The normal processes of landscape development in karstic areas may suddenly appear extraordinary if they occur in association with urban development. Sinkholes and water drainage are two concerns that require special attention in developed karstic areas. Some of the major issues are:
Localized and seemingly spontaneous subsidence in populated areas can be destructive to facilities and potentially life threatening. Most observed collapses occur in soils and sediments overlying karstic bedrock. In some areas, sinkholes may reach spectacular proportions and cause considerable damage. Probably the most catastrophic sinkhole event in recorded history occurred in December 1962, in West Driefontein, South Africa. Twenty-nine lives were lost by the sudden disappearance of a building into a huge collapse that measured over 180 feet (55 m) across (Veni et al. 2001).
Sinkhole collapses occur naturally; they also may be induced by human activities. Induced sinkholes generally develop much faster than natural sinkholes, although all collapse sinkholes require some dissolution of the underlying bedrock (Veni et al. 2001).
Urbanization increases the risk of induced sinkhole collapse. The risk of collapse may increase because of changes in land use, stream bed diversions, and impoundments that locally increase the downward movement of water into bedrock openings beneath soil; also greater frequency and magnitude of water-table fluctuations caused by urban groundwater withdrawal and injection (Veni et al. 2001).
The lack of surface water is characteristic of karst; most of the rain that falls on karstic landscapes drains into the ground rather than flows into surface streams. Sinkholes and cave entrances serve as drains to underground flow systems. In undisturbed karstic areas, the capacity of a sinkhole drain is more or less in balance with long-term climate and can drain the water produced by most storms. Water backs up only during large storms when input exceeds outflow (Veni et al. 2001).
Problems occur when the landscape is altered by urban development. Erosion, a common side effect of construction, transports soil to the lowest part of sinkholes where it can effectively clog the natural drain. Impermeable ground cover - such as roads, parking lots, and buildings - increase the rate of runoff and promote water collection.
Stormwater drainage systems, which direct water away from urban centers, and stormwater drainage wells, sometimes called drywells, are methods used to mitigate drainage problems. It is important, however, that methods to control runoff water incorporate practices that reduce the introduction of refuse and pollutants into groundwater.
Caves and Karst in National Parks