In this chapter I briefly review the biogeography of the North American cave and karst biota, then the many threats to the biota and the remedies that have been devised. I cite cases mainly from the United States of America, with a few examples from Canada, Mexico, Belize, and Panama (Figure 34.1, overleaf).

The study of cave biota in the United States began in the late 19^th Century, and has been especially productive since the 1950s (Barr, 1968). The first biological study of a Mexican cave was in 1866, and important studies were made in 1932 in Yucatán. Published works on the Mexican cave fauna accelerated since the 1950s (Reddell, 1981). For too long many biospeleologists believed that troglobites were rare in the tropics. However, it has become apparent that many troglobites exist in Mexico, Hawaii, and other tropical areas where the high biodiversity, complex geology, rugged terrain, and multiple isolating mechanisms provide many opportunities for speciation.

Peck (1997) tabulated the troglobitic fauna of the 48 contiguous states of the United States. There are at least 1307 troglobitic species in the U.S., with 401 aquatic species (31%) and 906 terrestrial species (69%). Peck thinks more species are to be discovered, but doubts there are 6,000 troglobitic species, as predicted by Culver and Holsinger (1992). In Southeast Alaska, two troglobitic Stygobromus amphipods are known from island caves; one also occurs in caves on Vancouver Island, British Columbia, Canada (Aley et al. 1994). Castleguard Cave, Alberta, contains Canada’s only other troglobite, Stygobromus canadensis (Holsinger 1997).

Reddell (1981) reported about 317 troglobites from Mexico, Guatemala, and Belize, and nearly 1,952 total species. Troglobites were about 16% of the total number of species, and about 25% of the troglobites were aquatic. Hundreds of new species awaited study and description at that time. The number of named troglobitic species today probably would be about 500, but no recent tabulation has been published (Elliott 1994b).

Based on the above studies and typical trends, I estimate that continental North America currently contains about 1,800 named troglobitic species, of which 25 to 30% are aquatic. In addition, caves harbor numerous bat species, which provide important ecological services to humankind, and provide shelter for numerous other vertebrates.

Karst environments, such as deep, moist sinkholes and limestone glades, sometimes have relictual plant species, such as the Hart’s tongue fern, a Pleistocene relict found in Ontario, Michigan, New York state, and cave entrances in Tennessee and Alabama (Evans 1982). A high degree of endemism occurs in plant species in the limestone glades of the southeastern U.S. (Baskauf 1997). The only known U.S. locality for the tropical hay-scented fern, Dennstaedtia globulifera, is in Fern Cave, Texas (Elliott 1994f). These patchy environments are just as vulnerable as the caves.

Five or six North American troglobitic species are thought to be extinct, but it is likely that others became extinct before they could be discovered or described (Table 34.1). It is certain that local populations of invertebrates, fishes, salamanders, and bats have been extirpated. Probably fewer than half of the U.S. troglobites have been described, and in Mexico that proportion is even lower. Since some species are endemic to a single cave or a small cluster of caves, and many caves have been disturbed, filled, quarried, mined, or polluted, it is possible that some species have disappeared recently without our knowledge.

The Valdina Farms Sinkhole salamander, Eurycea troglodytes, may be extinct. The salamander’s only known cave in Texas was used as a recharge well by the Edwards Underground Water District, which excavated a flood channel from a nearby creek to the entrance. In 1987 a large flood pulse cleaned out the cave. Also lost were a colony of 4 million free-tailed bats, Tadarida brasiliensis mexicana, and a rare colony of the leaf-chinned bat, Moormoops megalophylla. A follow-up study failed to find the salamander (Veni 1987; Elliott 1993a, 1994d). Jordan Hall Spring, in the sub-basement of the biology department at Indiana University, was altered by construction and then poisoned by a termite treatment. The spring used to contain an isopod and two amphipods, one of which was undescribed and known only from that spring (Lewis 1996a, John Holsinger, pers. comm.).

Hobbs (1997) reported that the carabid beetle, Pseudanophthalmus krameri, appears to be extinct or extremely rare. The beetle was known only from Cave Hill Cave, Ohio, which is in a mixed, mesophytic, second-growth forest with nearby fields, in a formerly glaciated area. The cave supports 23 terrestrial and aquatic species, and there were no obvious perturbations, although pesticide spraying could have occurred. Repeated visits and intense sampling yielded no individuals.

The Rich Mountain Cave beetle, Pseudanophthalmus krekeleri, described by Barr in 1965, occurred in only one cave in West Virginia. The cave was destroyed by a limestone quarry in the 1980s (Tina Hall, The Nature Conservancy, pers. comm.)

Some troglobites are extremely rare, so it is difficult to prove or disprove that they are extinct. For example, intensive surveys of the Blue River Bioreserve, Indiana, turned up a cave pseudoscorpion, Kleptochthonius packardi, which had not been seen for over 100 years (Lewis et al., 1997). The endangered Kentucky blind cave shrimp was thought to be extinct between 1967 and 1979 because it was not seen (Lisowski 1982, 1983). There had been a reduction in sightings of cave fish, crayfish, and shrimp just after a brine contamination from oilfields in 1961. The shrimp inhabits quiet, silt-bottomed pools in Mammoth Cave with seasonal sediment deposition. This was altered by river dams, which caused backflooding, backponding, siltation, temperature changes, and increased pollution input to streams in the Mammoth Cave System (Fig 34.2). The normal levels of backponding were documented by Hovey in 1897 and 1909.

The rarity of the blindfish Amblyopsis spelaea in Mammoth Cave and its absence from adjacent areas to the north led to speculation that it was either introduced or decimated during the long period when blindfish were sold as curios. Poulson (1968) examined historical and scientific records and found that most early records from Mammoth were for A. spelaea, not Typhlichthys subterraneus, which also inhabits the cave. A. spelaea was the dominant species in the Echo and Roaring River areas around 1890, and it is still common in Roaring River. The present rarity of A. spelaea is probably related to silting and flooding associated with deforestation, forest fires, and Lock and Dam #6 (Poulson 1968).

Table 34.3 lists the six continental U.S. bats that are currently on the U.S. endangered species list. All are dependent on caves for part of their life cycle, and disturbance has been the major factor in their decline. Indiana bats have lost significant numbers through disturbance of their hibernacula and improper gating, but also through loss of their typical summer habitat, which is under the bark of riparian trees.

My work in ten caves in Belize in 1992 and 1993 convinced me that insectivorous and frugivorus bats are often dependent on caves for roost sites in the tropics. In a cave called Actun Chapat I found the frugivore, Artibeus jamaicensis, and the insectivores Mormoops megallophyla and Glossophaga sp. (unpublished data). I found Carrollia sp., a frugivore in two other caves. "Ecotours" are increasing their visits to some of these caves. Disturbance of these cave roosts could lead to a decline in the reseeding of cut-over forest areas by bats.

McCracken (1989) questioned the utility of the IUCN Red Data Book, which listed 4% of the world’s bat species as endangered or threatened in 1988; he thinks the red list gives an inaccurate and minimal assessment of our current extinction crisis. This is because the list largely reflects our ignorance of the status of bats in most parts of the world. Besides the six endangered U.S. bats, another 13 U.S. species rely substantially on caves, but this does not mean that the other 34 U.S. bat species are doing well.

Table 34.4 lists thirteen U.S. species that are being seriously considered for listing by the USFWS. Some were petitioned by citizens and some were promoted by the USFWS because of imminent land development, as in the case of Cicurina wartoni (Ruth Stanford, USFWS, pers. comm.). In 1996 the USFWS discontinued the C2 list, a sort of "pre-candidate list".

The USFWS has received many petitions for additional listings of cave species, but has not acted on most of the petitions because of a lack of data, lack of funding and staff, and political pressure. Table 34.5 summarizes the 11 petitioned species that are still being considered, but at least 64 others that were petitioned were ruled "not substantial", "not warranted", "warranted but precluded", or "withdrawn" (Susan Lawrence, USFWS, pers. comm.). Frequently there was a lack of information in the petitions about population trends or threats. However, few of the species are under study because of little or no funding from any source.

Table 34.6 summarizes endangered "karst-dependent" species; these are not particularly cave-adapted, but are wholly dependent on the flow of karst springs. The San Marcos and Comal rivers in Central Texas are fed by large springs from the Edwards Aquifer. The rivers support multiple endemic species and contribute to the Guadalupe River, which feeds the San Antonio Bay estuary on the Gulf of Mexico coast, where there are important fisheries.

The process by which endangered species are listed in the U.S. is haphazard (Elliott 1990, 1992). Not only must there be adequate scientific knowledge to list a species, often there must be a political push in the form of a petition from conservationists and scientists. Consequently, unpopular or obscure species, even if they be declining, often are not listed because they are not championed by anyone. Although the cave species that are currently listed have multiple threats against them, other species may be in more danger than those already listed. Species on the list often serve, however imperfectly, as proxies that protect other species that should also be listed. Elliott (1991) analyzed the biogeography of more than 100 rare cave species in the Balcones Fault Zone of Texas. Travis County contains more than 30 troglobitic species endemic to that county, but only six of them were listed. His analysis selected a list of caves for the Balcones Canyonlands Conservation Plan that would protect all the the endangered species as well as most of the other rare endemics, all of which are vulnerable. That plan now includes about 65 caves, half of which concern endangered species. However, lack of funding has imperiled even those caves (Elliott 1997c).

The value of cave species to the public often is considered low, but cave species have potential scientific, practical, and educational value. To many, size or intelligence of the creature is equated with importance. Cave species may have good potential value to humans as "indicator species" in karst areas. That is, the decline of sensitive species because of pests or pollution may be a natural alarm for regulators and public health agencies. This is especially true of groundwater species, which may be affected by pollutants, pathogens, or nutrient stress over long distances. These contaminants can also affect people.

Declines in cave bat populations were noted as early as 1952 (Mohr 1972). Studies of troglobites lagged behind because of the small number of biospeleologists. Poulson and Kane (1977) outlined several kinds of disturbance in cave ecosystems. They gave examples from Mammoth Cave, and with a flow chart they illustrated the results and interrelations of these disturbances. For a scientific management program, they outlined the elements of a biological inventory coupled with environmental measurements, taxonomic identifications, and evaluation of results. Many of the threats discussed below are so interrelated that researchers have difficulty determining which threats cause the greatest problems.

Water projects have caused many problems for cave biota. The Mammoth Cave System, Kentucky, has the longest and best documented ecological history of any cave in North America. Mammoth Cave’s Styx and Echo river areas had an apparent decline of troglobites from the late 1800s to the 1910s or 1920s. In 1906, Lock and Dam #6 was installed on Green River below Mammoth Cave. Green River naturally backfloods into the cave, but the levels are higher now (Lisowski and Poulson 1981, Lewis 1982). Backflooding into Bat Cave killed 300,000 Myotis sodalis bats in about 1937 (Mohr 1972). From the late 1950s to the 1970s only large cavefish and cave crayfish were seen, and in low numbers. In the 1970s the Nolin River, a tributary to Green River, was dammed below Mammoth, and Green River was dammed upstream. Since then the maximum height of floods has decreased and the time to return to base-level flow after floods has increased. The Kentucky blind shrimp declined and is now found farther upstream in the cave. Poulson (1996) concluded that toxins and organic enrichment, though present, were not the cause of the declines in the biota, but siltation probably was the cause. Loss of nutrients also may have occurred (see below). The present rarity of A. spelaea is probably related to silting and flooding associated with deforestation, forest fires, and erection of Lock and Dam #6 (Poulson 1968).

Lewis and Lewis (1980) studied Caecidotea stygia and Caecidotea n.sp. in Mammoth Cave. Base level streams typically exhibit greater microhabitat diversity, and perennial water supplies, but environmental disturbances have reduced habitat diversity and introduced physical and chemical conditions which cause animal communities to deteriorate. Isopods do not usually occur in Echo or Styx rivers, except where large breakdown slabs remain above the silt or where boards from old tourist trails have been discarded into the stream, creating artificial microhabitats harboring isopods. The once abundant crayfish, Orconectes pellucidus reported by Hay in about 1902 in the River Styx are no longer common, since the food source (Caecidotea) has disappeared.

A water-quality monitoring program from 1990-1993 at Mammoth Cave National Park provided baseline data on spatial and temporal changes, but no biological data were gathered. Two rivers and eight springs were sampled synoptically in natural woodlands, agricultural lands, and areas influenced by urban use and oil and gas exploration. The monthly analyses of 36 parameters included discharge, turbidity, chloride, fecal coliform, and triazine herrbicides. The first 19 months of data demonstrated a strong correlation between drainage basin land use and water quality. In June, 1990, Echo River Spring backflooded from the Green River and received a large amount of flow from heavy agricultural land, whereas its normal input is low-turbidity water from parkland (Meiman 1993).

In the late 1970s the New Melones Reservoir was built on the Stanislaus River in California. About 30 caves were inundated, including McLean’s Cave, one of only two known localities for the troglobitic harvestman Banksula melones. The McLean’s cave community was transplanted to a nearby mine, but in a follow-up study it was found in 18 caves and is now considered safe (Elliott 1978, 1981). See further discussion of this case under Ecological Transplantation below.

The loss of recharge to and overpumping of a karst aquifer results in a gradual decline of water quantity and quality. The Devils Hole pupfish in Nevada is endangered by overpumping of the regional aquifer, which has reduced the fish to a tiny population at the bottom of a sinkhole (Elliott 1981). Other karst pupfishes are endangered (Table 34.6).

The Balcones Fault Zone portion of the Edwards Aquifer, Texas, supports more than 40 aquatic species. This unique community is in danger of being impacted severely by overpumping of groundwater, which will cause spring failures and dewatering of some of the system, and also cause encroachment of highly saline water into areas that now have high quality water. The average, annual recharge of 774,627,000 m³ is now approached by pumpage of about 666,080,000 m³ (Longley, 1991). Five endangered and one threatened species are dependent on this aquifer (see Tables 34.2 and 34.6 above).

The development of karst areas without regard to sensitive natural features has destroyed or filled numerous caves. In the Austin, Texas, area, caves are often searched out in advance of roads and buildings because of endangered species protected by the U.S. Fish and Wildlife Service (USFWS). The excavation of sealed cave entrances during karst studies may lead to drying of the entrance zone. However, this may be offset by increased nutrient input from organic detritus, colonizing cave crickets, bats, and other species, but pests, such as fire ants, may also invade the caves more easily (see further discussion below). Studies have shown that occasional feces deposited by visiting raccoons, who routinely use caves, enhances population sizes of terrestrial cave communities, therefore the opening of sealed caves may be beneficial to cave communities if inputs and disturbance are not excessive (Elliott 1994, Elliott and Reddell 1989, Reddell 1991, Reddell and Elliott 1991).

The mining of caves for saltpeter, bat guano, or other minerals, can have a drastic effect on bat colonies and other fauna. Mexican free-tailed bats, Tadarida brasiliensis mexicana, have been disturbed by some guano mining in Texas, while other miners may have aided the colonies by mining out rooms that might have filled with guano eventually. The better operations mine only in the winter when the bats are gone (Elliott 1994d)

Quarrying and road building has completely destroyed many caves, but has also revealed some significant caves that were put to good use. Inner Space Cavern, near Georgetown, Texas, was discovered in 1963 during construction of Interstate Highway 35. It proved to be an important biological and paleontological cave, and was so attractive that it was developed as a show cave in 1966. The cave also contains two endangered species, but it is threatened by road spills, quarrying (and its possible effects on troglobite populations and groundwater), utilities, and encroaching residential developments (Elliott 1994g).

The opening of large, second entrances can severely alter the meteorology of a cave, causing bats to vacate. Marshall Bat Cave, Texas, lost its free-tail colony after 1945, when a large, 40-m-deep shaft was dug into the rear of the cave to hoist out guano, causing too much ventilation and cooling of the cave (Elliott, 1994d). Free-tails require warm temperatures and large caverns for maternity roosts (Herreid, 1963, 1967). Mammoth Cave probably harbored Indiana bats prehistorically, before the entrance was modified to block incursions of cold winter air. The National Park Service is currently trying to reinstate the natural temperature profile of the cave (Rick Olson, pers. comm.).

Sealing caves can be very harmful to cave fauna—even an improper gate can harm bats and other fauna (see below). Although there is little direct information on the effects of actually sealing a cave, I have observed that areas of caves that are naturally sealed in calcite, or truly entranceless caves that were bored into, are rather depauperate. Poulson (1997) has noted the dry areas of Mammoth Cave caused by the sandstone caprock, which hinders percolation and food input. In the shallow caves of Central Texas, those areas with soil creeping in from plugged sinkholes, or near tree roots, or with feces from crickets, bats, or raccoons, have more abundant and diverse communities (Elliott 1989, Reddell and Elliott 1991, Reddell 1992). Some cave communities are highly dependent on cave crickets, which exit at night to scavenge on the surface; for example, different species of troglobitic beetles that prey on cricket eggs are found from Indiana to Alabama and Texas. Therefore, if entrances are sealed the cave cricket input ceases unless small holes still enter the cave.

Caves that are sealed under pavement or buildings usually receive less infiltrating water, and may become barren. For example, Mayor Elliott Cave, which was entranceless, was discovered under a street and a house in Georgetown, Texas, in May, 1997. Investigation of the cave showed that the speleothem areas under the house slab foundation were dry, and there was no fauna. Passageways under a street received infiltration from irrigation of lawns and leaking street gutters. A moist soil slope from a sink or crevice in the yard contained a delicate, endangered, troglobitic harvestman, Texella reyesi (Elliott 1997b).

Cases in which nutrient loss resulted in noticeable effects in a cave have been rarely documented; one that is often cited is Shelta Cave, in Huntsville, Alabama. Shelta had the most diverse cave community known in the southeastern U.S., but land development encroached on the cave in the 1960s and the townspeople were concerned about youths entering the cave. The cave harbored a large colony of Myotis grisescens, the endangered gray bat. The National Speleological Society purchased the cave in 1967 to save it, and they moved their headquarters to a building nearby. The cave was gated in 1968 with a strong, cross-barred gate that had been taken from an old jail. This gate, in hindsight, was inappropriate for bats, and they abandoned the cave within two years. However, the urbanization of the area might also have doomed the colony. In 1981 a modern, horizontal-bar, "Tuttle style" door was put on the gate, but no bats returned to the cave (Hobbs and Bagley 1989). This species, especially maternity colonies, usually does not tolerate even well-designed gates (Robert Currie, pers. comm.)

Studies by Cooper (1969, 1975) elucidated the rich aquatic community in Shelta Cave, with three species of extremely long-lived crayfish with low reproductive rates, a shrimp, cavefish, and numerous other troglobites. The aquatic system was dependent on food from bat guano, and it declined after the bats vacated. Cooper’s 1968-1969 census studies, when compared to data from 1985-1989 by Hobbs and Bagley (1989), showed that the bats left, crayfish decreased from a usual range of 49-250 (usually >100) to 0-10, cavefish decreased from "many" to 3-15, and that the Alabama cave shrimp dropped from 1-25 to none (Hobbs 1996). Hobbs and Bagley analyzed cave water samples and found small amounts of heptachlor epoxide (0.5 m g l^-1 in 1987, 0.04 m g l^-1 in 1988). The insecticide probably was leaching into the groundwater from treated house foundations in the area. The shrimp was known from two caves, and was listed as endangered in 1988 (Table 34.2), but has since been found in a river cave in the area (H.H. Hobbs, III, pers. comm.). It is still not certain whether the cave gate, which caused a nutrient loss by causing the bats to vacate, was the primary cause of the community’s decline, or if toxins and disturbance were also to blame. All of these factors probably played a role in the decline.

Poulson (1996) suggested that loss of fine particulate organic matter, caused by river damming, could have influenced the decline of aquatic fauna in Mammoth Cave.

Sometimes terrestrial invertebrate cave communities can survive well in urban areas. Elliott and Reddell (1989) found that Bandit Cave, under a wooded lot in a residential area of Austin, Texas, still contained all of the species found there in the 1960s. The owner protects the cave and raccoons still visit it, leaving feces. However, there are no real census data to properly evaluate the situation. It may be difficult to maintain aquatic communities and bat colonies in urban areas, depending on the species.

Enrichment appears to be a much more common problem in caves than nutrient loss. Pasquarell et al. (1993) reported on weekly water samples taken in the fall of 1990 from four springs in Greenbrier County, West Virginia. Besides atrazine herbicide being detected in all springs at low levels, mean nitrate levels were 13.6 and 10.8 mg l^-1 from two basins. Mean bacterial levels for the two basins were 101 and 139 fecal coliform colonies per 100 ml and 266 and 276 fecal Streptococcus colonies per 100 ml. Samples from nine cave stream sites had nitrates ranging from 13.4 to 63.7 mg l^-1. Fecal coliforms ranged from 110 to 28,588 colonies per 100 ml. One cave, which had the highest nitrates and fecal coliforms, receives flow from a sinkhole which is immediately adjacent to a feedlot on the surface. Species diversity in the latter cave was substantially reduced from that found in other, less contaminated caves. Aley (1997) mentioned the odor of animal wastes from a hog-raising operation permeating the air of one of the largest caves in Missouri.

A study of three caves in Cookeville, Tennessee, suggested a relationship between degrading water quality and reduced biotic diversity. Capshaw and Ament Caves, which receive sewage-contaminated runoff, were dominated by oligochaetes and dipterans, and had larger coefficients of variation for most water quality parameters than City Spring Cave (Pride et al. 1988).

Karstic groundwater is the major water source in the Yucatán Peninsula, and had a major influence on the Maya culture. In Mérida some wastewater is disposed of via deep-well injection, but its fate has not been traced. Pig farms and cattle ranches are another potential source of pollution, and use of fertilizers and pesticides threatens the local water supply in some areas. Solid waste is often dumped at the edges of towns or discarded into dry caves. Cenote Dzitya, near Mérida, was contaminated by a nearby pig farm, according to water chemistry and algal data. Preliminary data from 75 water bodies showed that undisturbed inland waterbodies contained relatively low concentrations of nutrients (0.6-16.0 µM NO₃ + NO₂, 0.1-6.0 µM NH₄, 0.2-1.8 µM P, and 2.3-74 µM Si), whereas culturally impacted ecosystems and coastal lagoons had evidence of enrichment (19-162 µM NO₃ + NO₂, 6-62 µM NH₄, 2.5-13.8 µM P, and 93-544 µM Si). A pig farm (Agropecuaria Yucatán) was constructed above Cueva de El Pochote, which contained a unique cave fauna, including Ogilbia pearsei, Ophisternon infernale, Creaseria morleyi, Creaseriella anops, and Typhlatya pearsei (Horst Wilkens, pers. comm.). Cenotes provide important habitat for stygobionts and other species, such as the threatened Morelet’s crocodile, and provide drinking water for endangered mammals such as the jaguar (Brenner et al. 1995). No studies of pollution effects on cave species of this region have been published to date.

In July 1993 I observed many annelid worms in a stream in Whispering Canyon Cave, in the Tongass National Forest, Southeast Alaska, which may have resulted from elevated nutrient loads from nearby logged areas (Aley et al. 1993). Problems caused by logging have been reported in similar cave areas on Vancouver Island, British Columbia, Canada. Many caves were choked with slash and sediments, and small buffer zones of uncut timber around caves were blown down by windstorms because they were inadequate in size and design (Pault Griffiths pers. comm., Blackwell and Associates 1995, Stokes 1996).

Enrichment is a common problem, especially in show caves, caused by lunch rooms, garbage, litter, sewage, cave lint, and lighting that promotes the growth of cyanobacteria. These disturbances perturb the distribution and abundance of species within the cave. Examples from several prominent caves are given below.

Mammoth Cave, Kentucky— The cave amphipod, Crangonyx packardi, used to be common in Shalers Brook in Mammoth Cave, which at one time was enriched by sewage effluent from the Mammoth Cave Hotel. The sewage problem has now abated and C. packardi is no longer there, but Stygobromus vitreus, which is more cave-adapted, is present (Lewis 1984). The artificial Crystal Lake, near the Frozen Niagara Entrance, was created from damming a short shaft drain, and was used for boat rides. Barr and Kuehne (1971) reported Caecidotea stygia and Orconectes pellucidus there, but Lewis (1984) found neither and noted that, "Prying boards from the bottom of the lake uncovers a black layer of anerobically produced sapropel with its characterisitic accompanying odor, a habitat which does not seem conducive to cavernicoles."

Pollution from the flushing of a Job Corps sewage lagoon in the summer of 1967 reduced the complexity of the cave community as seen under unpolluted conditions in 1966. It also reduced numbers of terrestrial organisms trapped per trap-day by more than ten-fold at two stations near the headwaters of Eyeless Fish Trail. Organic content was 240% of the 1966 level. A "high-tide-line" of cyanobacteria was indexed, like that associated with foam and coliform pollution in Keller Shafts (Poulson 1967). The Job Corps Center was removed several years later. Attention was focused on potential sources of contamination. The U.S. Environmental Protection Agency issued an Environmental Impact Statement on Mammoth. New wasteload allocations were to be issued for public treatment plants in the area. The National Park Service financed a regional sewage treatment plant (Poulson 1997).

At Mammoth most contaminant transfer occurs in the first flush of rainfall events. Farm lands on karst contribute nonpoint-source sediments, pesticides, herbicides, animal wastes, and bacterial loads to cave streams. Urban development brings sewage, solid waste, and leakage from buried storage tanks and pipelines. Unnatural sediment deposition, entry of exotic species, and changes in deposition of particulate organic matter from upstream threaten base-level ecosystems (Poulson 1996, 1997).

The pathogen Salmonella chloera-suis chloera-suis was recovered in water from the Hawkins River and Owl Cave at Mammoth Cave National Park, and Salmonella sp. from Owl Cave sediment. Echo River in Mammoth Cave lacked Salmonella. A possible source of the bacteria was failed septic systems (Rusterholtz and Mallory 1990).

Poulson (1992a) developed community signatures for different kinds of pollutants, contrasting acute toxins, chronic toxins, organic enrichment, and siltation. "Indices of biological integrity" include number of species and metrics for species’ well-being and the presence and relative abundances of tolerant and intolerant species. Gross enrichment is usually point-source, and can be detected as a slippery biofilm on cave stream rocks, with stimulation of short-lived troglobites like flatworms and isopods.

As in many show caves, plant growth around electric lights is a continual problem. Algae and moss protonema had to be steam-cleaned from ceiling formations at Frozen Niagara in Mammoth Cave (Aley 1997).

Enrichment sometimes comes from unusual sources. Lisowski et al. (1986) found that release of oil brines or sulphur water from oil and gas exploration could have major adverse impacts on the Mammoth Cave System. They found sulphur bacteria in Sulphur River, Parker’s Cave, which is strikingly different from other cave streams in the region. The water contained high NaCl (up to 1.6% Cl^-) and sulfide. The substrate of the stream was covered with a white mat-like material several centimeters thick. Two sulphur oxidizers, Beggiatoa alba and Thiotrix tenuissima were in the mat along with others. Water and mat samples contained a number of protozoa in 12 genera, including flagellates, ciliates, and amoeboid forms. Two species of annelids, a cave snail, five species of collembolans, a cave carabid, a linyphiid spider Phanetta subterranea, and several species of mites were found. Water droplets on a spider’s web were milky white because of rod-shaped bacteria, and had a pH of 0.13. Northup et al. (1997a) characterized the bacteria as sulfide-oxidizers, and found phylogenetic relationships to deep-sea-thermal-vent and tidal-mud-flat communities.

Hidden River Cave, Kentucky— The Hidden River (Horse) Cave system was commercialized in 1916, co-existing with water pumping and hydroelectric generating systems. Hidden River Cave had a troglobitic fauna, with Typhlichthys cavefish, Orconectes crayfish, and Caecidotea isopods. However, increasing groundwater contamination from indiscriminate sewage disposal led to closing of the cave's tourist operation in 1943. Sewage from Cave City and Horse Cave, and creamery wastes were introduced into the stream at Horse Cave. In 1970 waste water from a chrome-plating factory was added to the sewage plant effluent entering the cave. The troglobitic community was extirpated as a result of degradation of the cave. Hidden River Cave, South Branch contained large numbers of red tubificid worms at the edges of stream pools, "sewage fungus" (characterized by the bacterium Sphaerotilus natans), nearly anaerobic conditions, low nitrates, high nitrites, and blackened iron sulfide. In 1983 Hidden River, East Branch, had recovered much of its natural character by the time it reached Hidden River Cave from the Cave City treatment plant. The water was nearly saturated with oxygen and probably supported troglobites. In 1989, new sewage-treatment facilities were opened and the flow of effluent to the cave stopped. By about 1995 the original animal community had substantially recolonized the once-heavily-polluted section of the cave from relatively unpolluted, upstream tributaries (Lewis et al. 1983, Lewis 1996a). Such an outcome could not have occurred in many other hydrologic situations. Today, visitors can take an ecological tour into the cave and observe the troglobites.

Carlsbad Cavern, New Mexico— Except for the Bat Cave section, where a large free-tail colony resides, Carlsbad had a sparse fauna which became disturbed after the cave opened to the public in 1923. Bailey (1928) observed that the Lunch Room in the cave was already causing Peromyscus leucopus mice to invade the King’s Palace area, the southern Big Room, and the lower cave in the 1920s. Although this species commonly is found in cave entrance areas, where it feeds on crickets, the mice already were permanent residents deep in the cave, as evidenced by females with embryos or nursing young. Bailey found cave crickets and tourists’ lunches in the mice’s stomachs.

Studies of rhaphidophorid crickets in Carlsbad have shown unnatural distributions. Ceuthophilus carlsbadensis naturally occurs in the Bat Cave section. C. longipes now occurs far from the entrance in total darkness in the Sand Passage. In the Left Hand Tunnel (just past the Lunch Room) C. carlsbadensis and C. longipes occured near reliable food sources such as trash containers. A greater number of Left Hand Tunnel crickets were found directly behind the gate about 100 m from the Lunch Room and also 300 m from there at a probable oviposition site. This appears to be an artificial entrance situation, with the lighted Lunch Room serving as an ersatz outdoors, complete with food, and the crickets hiding in a darkened area behind the gate, and ovipositing farther back. Any food dropped by park visitors attracts crickets to feed upon it. Rangers have reported crickets feeding on bat carcasses in the Queen’s Chamber and on human feces left near or on visitor trails (Northup and Kuper 1987, Northup et al. 1987, Northup et al. 1989). The National Park Service instituted tighter housekeeping controls on the Lunch Room operators, and now removes the contents of all trash barrels by the end of the day to combat the large number of raccoons that invaded the cave at night (Dale Pate, pers. comm., National Park Service 1996). The National Park Service’s new management plan (1996) would remove the facilities from the Lunch Room.

Aley et al. (1985) conducted studies on exotic plant growth in Carlsbad Caverns. They identified 26 species of algae, plus moss protonema and two ferns. There may have been a total of 100 to 200 species of algae growing in the cave. The growths in the cave were about 70% cyanobateria, 20% green algae, and 10% moss protonema. Diatoms were present in about 25% of all clusters, and a few yellow-green algae were present. Many of the algal genera, and three of the algal species, in Carlsbad have also been found growing in total darkness in other caves. Algal growth, once abundantly established due to artificial lighting, will not quickly disappear if it is deprived of light. Light intensities were measured at a number of sites. In alcoves the minimum light intensity threshold for algal growth had a mean value of 17.2 lx (1.6 fc) with a standard deviation of 7.5 lx. In nonalcove sites (most situations) the mean threshold was 47.4 lx (SD = 20.5 lx).

Cave lint studies more or less started in Carlsbad Caverns in connection with annual "lint camp" cleanups by volunteers. Jablonsky et al. (1995) placed "seeded lint" (which looks different under ultraviolet light than normal lint) on the trail, and found that it moved up to 100 m down the trail; much of it moved to the edge or off the trail. Slides of lint contained synthetic and natural fibers, dirt, wood, insect parts, human hair, animal fur, fungus, processed tobacco, paper, and other things. Unidentified mites were seen in some of the samples (Pat Jablonsky, pers. comm.).

In Carlsbad Cavern Elliott (1997a) studied old woodpiles that probably were remnants of structures installed in the 1920s. Most of the wood was depleted of nutrients and supported little visible fungal or bacterial growth any longer. However, some wood was up to 80% water by weight, and served as a moist substrate. Some piles contained almost no invertebrates, while others were a haven for several species. He recommended removing most of some of the piles over a period of time, leaving a small residue for the fauna to utilize. He studied Signature Pool near the trail, which is a microcosm of algae, eyed flatworms (Phagocata sp.) and eyed copepods that probably were introduced; the small community is driven by a light bulb hanging over the pool. In another part of the cave a sewage leak infiltrated to the cave and caused some localized fungal growths and swarms of fungus gnats, which supported a local community of spiders.

In another part of Carlsbad Caverns National Park, urine and feces left by cavers in Lechuguilla Cave contaminated some areas with bacteria despite strict rules about carrying wastes out of the cave. The National Park Service was concerned about such microbiota altering the cave environment, possible effects on any cave-adapted species, and health effects. Allowing contaminated areas to "rest" for a few months often resulted in the disappearance of the exotic species, provided that visible residues were removed (Northup et al. 1997b).

A Midwestern Show Cave— In a bizarre case in 1993, earthworms came out of the cave walls and rocks fell out of the ceiling for an extended time. I consulted for the cave management, who thought that the earthworms were causing the problems, and that they should be exterminated. Systematic observation and sampling revealed that the earthworms were following infiltrating sewage into the cave from broken sewer lines and forgotten, leaking, septic tanks built on top of the cave. The epikarst in that area, though mantled with good soil, was highly transmissive. Dye traces proved that the cave was "cross-connected" to many input points on the surface, including septic systems. Bacteriological sampling showed the presence of E. coli, Salmonella, and Shigella in many air and water samples from the cave. Two European exotic species of earthworm, Eiseniella tetraedra and Dendrobaena rubida, were found crawling on wet surfaces in the cave, and were actually eating softer, marly beds of rock, which were probably laden with bacteria. There was little or no odor in the cave, but airborne bacteria levels were high enough to cause concern about prolonged exposure. Clay banks in some areas were festooned with rich and colorful fungus gardens, which were inhabited by invading hothouse millipedes and sowbugs. No troglobites could be found in the cave. After these initial findings, the owners initiated intensive maintenance and repair of the septic system and took steps to prevent infiltration of nutrients from the theme park above the cave. The earthworms were not killed, but were to be considered as "friends" who would eat up much of the contamination. After about two years of work, the management reported that the cave was returning to normal biologically, and that rockfall (which probably was related to both high water infiltration rates and earthworm activity) had decreased to a low level (Elliott, unpublished data).

As we have seen above, enrichment of caves with nutrients can bring sewage bacteria and fungi, red tubificid worms, earthworms, hothouse millipedes, sowbugs, and other exotic species into the cave. In Central Texas red imported fire ants, Solenopsis invicta, began invading caves in 1988, not because of enrichment but because of the ongoing adaptation of this Brazilian pest to the southern United States. The multiple-queen colonies live in soil mounds, but the workers invade the shallow caves in the summer, when the soil is hot and dry, and forage for moisture and food in the caves. They have been observed attacking and carrying off various troglobitic species and cave crickets. Some caves in the Austin, Texas, area are so overrun with fire ants in the summer that it is unsafe to crawl into the caves. The ants retreat to the surface again in the autumn, but can reproduce year-round if the weather is mild. The best control method is to kill the mounds with boiling water. This is instantaneous but labor intensive; however, it avoids the problem of using insecticidal baits, which could be picked up by cave crickets as they forage on the surface at night (Elliott 1990, 1991, 1992b, 1993a, 1993b, 1994b, 1994d, 1997b; Elliott and Reddell 1989; Reddell 1991).

Chemical Pollution

Cave life has been affected more often by water-borne pollutants than by solid waste. In this section I mostly discuss chemical pollutants, but waste from sewage, agriculture, or cavers can have toxic effects too, and they often go together.

Spent carbide from acetylene lamps was the most common poison recognized by cavers in their environment. Until the 1960s many cavers dumped or buried their spent carbide in caves, but the practice was discouraged. Peck (1969) pointed out that the calcium hydroxide in spent carbide was poisonous to cave fauna, which he demonstrated in experiments with the cave beetle Ptomaphagus hirtus. Fortunately, carbide dumping and use is declining. I found no reports of any kills resulting from spent carbide, but the effects would be subtle. Batteries left by careless cave visitors can leak toxic materials, including mercury.

The most dramatic kill of cave biota yet reported was in November of 1981, when an estimated 80,000 l of liquid ammonium nitrate and urea fertilizer spilled at a pipeline break near Dry Fork Creek, Missouri. Dry Fork is a losing stream and a recharge area for Meramec Spring, the state’s third largest spring. Seven days following the break, dissolved oxygen at Maramec Spring, a distance of 21 km from the break site, dropped to less than 1 mg l^-1 for nine days resulting in a loss of over 37,000 fish at a hatchery. Ammonia and nitrate nitrogen concentrations in the spring were elevated for over 38 days. Aquatic organisms killed included >10,000 of the rare Salem cave crayfish Cambarus hubrichti, nearly 1000 of the southern cavefish Typhlichthys subterraneus, which had not previously been reported from the Meramec basin, and a small number of the Ozark blind salamander Typhlotriton spelaeus. Numerous other cave organisms killed included amphipods, isopods, and gastropods, but no attempt was made to quantify these losses (Crunkilton, 1985). A few years later cave divers observed some of these species in side passages or pockets in the spring system (Eugene Vale and Jo Schaper, pers. comm.). Baseline data and real followup data are lacking, so the long-term effects of this spill are still unknown. This incident points up the need for baseline data and ongoing hydrological and biological monitoring.

Perhaps even more devastating than the Meramec Spring kill was the presumed sterilization by nitric acid of caves at the Indiana Army Ammunition Plant, near Charlestown, Clark County, Indiana. The plant was constructed during World War II for the production, shipping, and storage of nitrocellulose propellant. The caves of the Jenny Lind Run drainage received an estimated 22,500 gallons per minute of nitric acid as a waste product of the nitrocellulose production process. Now, 50 years later, six species of troglobites have recolonized the nitric acid caves of Jenny lind Run. The aquatic troglobite Caecidotea stygia has recolonized all of the caves and springs on Jenny Lind Run. Terrestrial troglobites inhabiting the caves include Pseudotremia nefanda, Litocampa sp., Pseudosinella sp., Spelobia tenebrarum, and Phanetta subterranea (Lewis 1996b). We do not know the true composition of the original fauna.

Bats with insectivorous diets, long life, and long migrations are sensitive to biological amplification of pesticides. Mexican free-tailed bats, Tadarida brasiliensis mexicana, at Carlsbad Cavern declined from 8.7 million in 1936 to only 200,000 in 1973, at least partly due to DDT residues in their diets. DDT had been used extensively on irrigated cotton in the Pecos River Valley nearby. Studies showed that DDT and DDE (a metabolite) residues in the colony did not decline much after the insecticide was banned in the U.S. in 1972. After 1980 the residues declined slightly, but rose again in 1987-1988, perhaps due to DDT usage in Mexico. Gray bats, Myotis grisescens, from two maternity caves in Franklin County, Missouri were killed by dieldrin, a metabolite of aldrin, in 1976-1978. Residues of dieldrin and heptachlor epoxide, which had been used locally on corn, were found in guano and insect prey. One colony declined from 1,800 in 1978 to none in 1979-1982. Dieldrin also killed gray bats at three caves in Boone County, Missouri (Clark 1988). Peck (1974) reported that public health authorities fumigated Chilibrillo Cave, Panama, to remove the bat colonies shortly after his survey there. The effect on invertebrates was not studied. Other factors have also reduced bat populations (see below).

[aldrin = (1R,4S,4aS,5S,8R,8aR)-1,2,3,4,10,10-hexachloro-1,4,4a,5,8,8a,hexahydro-1,4:5,8-demethanonaphthalene.  dieldrin = (1R,4S,4aS,5R,6R,7S,8S,8aR)-1,2,3,4,10,10-hexachloro-1,4,4a,5,6,7,8,8a-octahydro-6,7,epoxy-1,4:5,8-demethanonapthalene.]

Sewage and gasoline leaking from a service station into groundwater poisoned parts of theYoung-Fugate Cave System, Virginia. The cave is inhabited by two troglobitic crustaceans and is the only known locality for the cave beetle Pseudanophthalmus holsingeri (Table 34.4). The service station was removed. Contaminants that have fouled Virginia's karst include spills or leaks of petroleum products, herbicides, sheep and cattle dip, solvents, fertilizers, sewage, milk, cream, and the leachate of improperly disposed waste materials (Hubbard 1996, Hubbard and Balfour 1993). In 1995, a resident crustacean was decimated in Wildcat Saltpeter Cave, Virginia, by diesel fuel from a leaking underground storage tank (David Hubbard, pers. comm.). Sawdust and bark caused a die-off of the crustaceans Lirceus usdagalun, Crangonyx antennatus, and Caecidotea recurvata in Thompson Cedar Cave, Virginia (Culver et al. 1992).

Brine pollution from the Greensburg Oilfield upstream from Mammoth Cave began in 1958 and continued for several years. The chloride ion allowed Hendrickson (1961) to estimate the contribution of water from Green River to the cave through Styx River Spring and out again at Echo Spring— about 40% from Green River and 50% from local groundwater sources. There was a reduction in sightings of cave fish, crayfish, and shrimp just after the brine contamination. A massive cave crayfish kill occurred in Mammoth Cave’s Hawkins River under Joppa Ridge in 1979, probably from a petroleum spill or leaking underground gasoline tank. An accident in 1980 between two trucks spilled ink and cyanide; quick action by officials prevented large quantities from entering Hawkins River and killing all the aquatic life downstream to the Green River. At Mammoth Cave most contaminant transfer occurs in association with rainfall events (Poulson 1996).

Slash and sedimentation from logging can choke cave entrances and alter aquatic communities. Logging and road-building practices in the karst areas of the Tongass National Forest, Southeast Alaska, caused some caves to receive elevated sediment loads, which could also carry diesel fuel and other petroleum products, which could affect cave stream communities, salmon runs downstream, and drinking water sources (Aley et al.1993, Elliott 1994a). Similar problems have occurred on the karst of Vancouver Island, Bristish Columbia, Canada (Blackwell and Associates, Ltd. 1995).

Waste dumping into caves is occurring in some parts of Mexico. Sótano de Médico, near Tlamaya, San Luís Potosí, was named for the large amount of medical waste, including used syringes, that had been dumped into it (Minton 1992). In July 1996 I personally observed used pesticide drums of chlordane and methamidophos, both highly toxic insecticides, in Toxic Sink, Coahuila (Fig. 34.3). Nearby, we found medical waste, including syringes, in Pozo del Cañon El Buey (Fig. 34.4). As mentioned above, fertilizers and pesticides threaten the local water supply in some areas of Yucatán.

Bosnak and Morgan (1981) experimentally determined the 96-hour LC50 values for cadmium, zinc, and total residual chlorine for two asellid isopod species from Tennessee, Caecidotea bicrenata (Stafford), a troglobite from Merrybranch Cave, White County, and Lirceus alabamae (Hubricht and Macken), an epigean form. The epigean form was more sensitive to heavy metals, and there was no significant difference in sensitivity to chlorine.

In an experiment in a remote area of Mammoth Cave, Rusterholtz (1989) dosed core samples of saturated sand with 5 m g of chlordane per g of sample for 30 minutes, and observed a 25.8% decrease in respiration. Cell counts were 6.2 x 10⁵ - 1.5 x 10⁶ cells per gram, with over 50% of the total cells actively respiring before treatment. This shows that even a very dilute slug of pesticide can kill or suppress microbes in cave sediments.

Nicotine is a powerful insecticide that was extensively used to fumigate greenhouses before synthetic pesticides became popular (Feinstein 1952). Howarth (1983) warned against the use of tobacco in caves because of nicotine, but there are about 4,000 other harmful chemicals in tobacco smoke, including acrolein, formaldehyde, a -benzopyrene, and carbon monoxide. Elliott (1995) improvised an exhaust system for welding fumes during the construction of a bat gate in Gorman Cave, Texas; however, the system was overwhelmed by the workers, who smoked cigarettes in the cave, creating a cloud of particulates. NO and CO were within acceptable limits defined by the U.S. Occupational Safety and Heatlh Administration for workers, but equipment was lacking for measuring other contaminants from tobacco smoke. Jablonsky et al. (1995) found processed tobacco in cave lint, but it was not quantified.

Welding fumes can be very toxic, especially if the metal being welded contains zinc or other elements. Welding in caves should be preceded by a study of air movements to see if contaminants will be naturally blown out of the cave entrance, or else a temporary exhaust system should be used (Elliott 1995).

A few examples of the numerous bat kills are provided. As mentioned above, backflooding from the dammed Green River into Bat Cave, Mammoth Cave National Park, killed 300,000 M. sodalis bats (Mohr 1972). In 1960 three boys intentionally killed 10,000 M. sodalis bats in Carter Caves State Park, Kentucky (Mohr 1972). In 1961 an entire colony of Myotis velifer was killed or driven off from Chinaberry Cave, Williamson County, Texas, by an intruder using a .22 caliber rifle with rat-shot (Elliott 1994d). Eagle Creek Cave, Arizona, housed a Mexican freetail colony of 25 to 50 million in 1964, but the population shrank to 600,000 by 1970 (Mohr 1972), possibly because vandals disturbed and shotgunned the bats; DDT may have also been involved. In 1973 a developer filled Bear Cave, Bexar County, Texas, with large boulders, sand, and gravel, out of fear of liability because a person had been stuck in the entrance and had to be rescued; at least 20,000 bats (probably Myotis velifer) were roosting in the cave at the time (Elliott 1994d). In 1983 locals shotgunned bats, sprayed them with gasoline, and set them on fire in Walkup Cave, Hardeman County, Texas. Walkup was an important roost for Myotis velifer, Eptesicus fuscus pallidus, and Corynorhinus townsendii pallescens (Elliott 1994d, 1994e). In 1987, four men were convicted of shooting and crushing to death at least 66 (but probably several hundred) endangered Indiana bats, Myotis sodalis, in Thornhill Cave, Kentucky (Foster and MacGregor 1987).

In Ontario, Canada, Myotis lucifugus and other species declined in most of the unprotected caves and mines. The commercialization of Fourth Chute Cave, Quebec, Canada, eliminated the cold air circulation where the largest known population of Myotis leibii in eastern North America hibernated and the bats abandoned the cave (Mohr 1972). A colony of Leptonycteris sp. was killed or driven off by locals from a cave near Mezcala, Jalisco, Mexico, sometime between 1993 and 1996. The people probably were after the common vampire, Desmodus rotundus, which inhabits another cave nearby (Mario Sgro, pers. comm.). Many other cave bat colonies have been destroyed in Mexico in efforts to kill vampire bats, or from guano and phosphate mining of caves.

A general decline in many species of bat has caused great concern by bat biologists and conservationists. Bats are especially sensitive, even to human disturbance as slight as travel past their hibernating or nursery roosts. Continued disturbance can cause bats to abandon a cave. Disturbance during either summer or winter is critical since only a few caves have suitable microclimates for colonial bats (Mohr 1972, Poulson 1976). Disturbance and arousal of hibernating bats can cause 10 to 30 days of fat to be used (Brady 1982).

The banding of bat wings with bird leg bands was widely used by bat biologists from 1932 to about 1960, but the practice ceased when biologists became aware of the high mortality rate from the bands, which tore wing membranes and injured bones. Ironically, the banding studies alerted biologists to the ongoing declines of cave bats as early as 1952, some of which was caused by banding and collecting, but more of which was caused by habitat destruction, disturbance, and insecticides (Mohr 1972). The steady recovery of M. sodalis in Bat Cave, Mammoth Cave National Park, Kentucky, was reversed after a biologist banded all 250 in 1971; the population dropped to only 68 in 1975. College classes and tourists at some show caves commonly visited bat roosts until the 1970s. Biologists adopted lipped bands, and today they use tiny markers or radio transmitters glued to fur.

Overcollecting and handling of animals was an early concern of biospeleologists. Sullivan (1956) cautioned against excessive collecting of specimens, and the NSS adopted a conservation policy that discouraged collecting by amateurs or for any commercial use. Overcollecting was feared to have caused the decline of the cavefish Amblyopsis spelaea in Mammoth Cave, which were sold as curios in the 19^th Century (Poulson 1968). Overcollecting can threaten small populations with low reproductive rates, as in the case of Shelta Cave, where some crayfish do not become sexually mature until they over 40 years old. Generally, larger troglobites, such as cavefish, salamanders, and crayfish, may be long-lived, have small population sizes, and reproduce slowly; therefore collecting should be highly restrained. Smaller, more abundant troglobites, such as some amphipods, isopods, millipedes, and beetles, may withstand collecting better. However, some small species are exceedingly rare, so collecting should take that into account. Culver (1982) emphasized restraint in collecting by admitting that he had caused a severe decline in the populations of several cave isopods.

Overuse by visitors may cause compaction of substrates with disturbance or loss of microhabitats for small, cryptic species. Many troglobites are thigmotactic, that is they like to hide under rocks. The effect of trampling on such species has not been adequately studied.

Isolation

The isolation of caves and karst areas by land development, road-building, utilities, and quarries, rarely has been addessed in the academic scientific literature but is a common concern in the applied scientific literature. The concerns are at several levels: potential alteration of hydrologic inputs to the cave, loss of nutrient inputs by making intervening areas unsuitable for trogloxenes like cave crickets and raccoons, and vegetational changes.

A large quarry near Inner Space Cavern, Williamson County, Texas, probably destroyed many caves since 1963. This quarry may be creating a barrier to subterranean fauna in the narrow band of Edwards Limestone south of Inner Space Cavern. For several reasons, and as a hedge against the extirpation of some populations, the species recovery plan for seven terrestrial troglobites in that area calls for at least three cave preserves in each recognized "karst faunal zone", each of which is based on geology and recognizable cave faunas particular to karst blocks (O’Donnell et al. 1994, Veni 1992).

It has become axiomatic that baseline faunal surveys with simultaneous monitoring of ecological factors such as temperature, humidity, moisture, air movements, and nutrient inputs, are essential for understanding changes in cave faunas (Poulson and Kane 1977, Elliott and Reddell 1989, Perkins 1990, Elliott 1994, Northup and Welbourn 1995, Lewis 1996a). Cave faunas change seasonally and in response to climate. Initial faunal surveys can be accomplished in several ways, including hand collecting, baiting, Berlese extraction, and pitfall trapping. Once a fauna list is compiled, census work in different seasons and years increases the range and value of the data set. Large fluctuations in some trogloxenic populations can occur on an annual time scale; for instance, cave cricket populations in some Central Texas caves dropped by half after a drought year in 1996 (Elliott, unpublished data). Historical data from the Mammoth Cave ecosystem over 100 years have been useful in understanding the current ecology of the cave. Comparative studies of different types of cave communities give us a better idea of how to manage a particular cave, such as a show cave that has been perturbed for many years.

Early cave gates were sometimes harmful to natural cave communities, especially bats; they were either too weak to exclude vandals, or too restrictive for bats and air flow (Elliott 1996). MacGregor (1993) found that some early gates actually caused most of the decline in Indiana bats (Myotis sodalis) since the 1950s and 1960s. These gates often had criss-cross bars or steel plates, which blocked air flow, and bats actually had to land on some of them to get through. Some gates had concrete sills or walls that projected into the passageway, restricting the flow of cold air along the floor, which changed the temperature profile of the cave. Indiana bats prefer very cold caves for hibernation, so they abandoned some caves that had become too warm. Better gates have allowed some of those populations to increase again. The standard bat gate now recommended by the American Cave Conservation Association, Bat Conservation International, USFWS, and NSS, is usually made of horizontal pieces of stiffened angle iron spaced at 15-cm (5.75-in.) intervals, with vertical supports no closer than 1.2 m (4 ft.) apart (Tuttle and Taylor 1994, Elliott 1996b). Some bat species do not tolerate gates at all, while some tolerate them better if the gate is built inside the cave instead of at the entrance, where there is more light and a higher risk of predators lurking (Robert Currie, Merlin Tuttle, pers. comm.). As mentioned above, Myotis grisescens vacated Shelta Cave after a gate was installed. Tadarida brasiliensis mexicana, the Mexican free-tailed bat, cannot tolerate gates because of its flight geometry and huge colonies.

Helf et al. 1996) emphasized the importance of protecting and managing cave crickets at Mammoth Cave. Vale and Jones (1993) restored microclimates in Onondaga Cave, Missouri, by plugging artificial entrances. In Texas, many caves have been gated for the protection of endangered or rare troglobites. Such gates may have tight spacing of the angle iron bars, but have animal access holes at least 20 cm in diameter built into the edge to allow cave crickets, raccoons, and other fauna to pass through (Fig. 34.5). Conservationists have made so many innovations in cave gate design and construction that the NSS’s gating handbook (Hunt and Stitt 1975) is being revised by the American Cave Conservation Association, Bat Conservation International, NSS, and USFWS.

Cave Restoration

Cave restoration projects are beneficial in removing harmful materials, trash, and graffiti. Some precautions are needed to avoid stressing cave communities that may have colonized organic materials, particularly old woodpiles that may be a haven for invertebrates (see discussion of Carlsbad woodpile study above). Elliott (1982) and Hubbard (1995) emphasized that wood should be examined by a biologist during cleanup projects or left alone. Such woodpiles may have attracted a large population of invertebrates over decades of time, and to remove it suddenly may, in effect, trap out a significant portion of the population in that area of the cave. Oftentimes such wood can be removed gradually and a small residue kept to provide habitat for the remaining fauna (Elliott 1997a). An important concept is to give some caves or microhabitats time to "rest".

Aley (1972) successfully killed algae, moss, and ferns growing near electric lights with a steam generator in Blanchard Springs Cavern, Arkansas, without damaging speleothems. Aley (1985) found that in Carlsbad Cavern lighting in moist alcove sites should be <9.7 lx. In moist nonalcove sites lighting should be <30.1 lx. Some studies were also conducted on chemical plant control agents. The best agent for general plant control appears to be 5.25% sodium hypochlorite (bleach) solutions. Copper sulfate and calcium hypochlorite solutions have caused damage to cave features when test-applied in Carlsbad Caverns.

Wildlife rescue operations have been used often for big game, but the concept rarely has been applied to cave animals. Ezell’s Cave, Texas, had been sealed by the owner to keep out intruders, but the loss of the bat colony and its guano was thought to have contributed to a decline in the resident population of Typhlomolge rathbuni salamanders. In 1970 biologists twice attempted to re-establish Myotis velifer bats in Ezell’s. Bats were captured in Northwest Texas, but they did not stay at Ezell’s Cave in Central Texas for even a day. This species is adaptable and will readily colonize newly opened caves, but the trip and handling probably was too frightening for them (Elliott 1993a. 1994d).

In 1976 and 1977-1978 a threatened population of harvestmen was transplanted from McLean’s Cave, California, to a nearby mine (Elliott 1978, 1981). Banksula melones, a troglobitic opilionid, was known from just two caves at the time, one of which was threatened by quarrying. The other cave, McLean’s, was scheduled for complete inundation by the New Melones Reservoir. The U.S. Army Corps of Engineers, which was building the dam, supported the project so as to avoid an endangered species listing. During the second, larger project, the cave population was intensively collected for three months, and the community of about 30 arthropod species transplanted to the Von Trump Mine, now called the "Transplant Mine". The mine was stocked like a terrarium with cave soil, rocks, and rotting wood from the surrounding area. The cave soil and fauna were brought in insulated containers to the mine and carefully placed in higher areas to avoid the minor flooding that sometimes occurs from seepage. A follow-up visit 1979 revealed that the cave community was doing well, although the population ratios of some of the species had changed dramatically. Thomas Briggs (pers. comm.) returned to the mine in 1996 and found that B. melones still inhabited it.

Transplanting cave fauna is an experimental technique, and it cannot seriously be considered a good solution for endangered cave faunas. Despite the apparent success of the "New Melones Transplant", several philosophical and practical problems were pointed out by Elliott (1978, 1981). Assuming that the transplant would work, one must have a suitable, "empty" habitat to transplant to. In this case, the Transplant Mine had a cave-like microclimate, was only 50 years old, and was excavated in Calaveras Limestone, which is the major speleifer in the area. However, transplanting to a natural cave would present three problems.

Ecological transplants have other potential problems: replenishment of nutrients (the Transplant Mine has to be restocked with wood occasionally as it has no sinkhole-like entrance), lack of commitment by the funding agencies for long-term monitoring of the transplant (the federal government provided no such funding), and using the technique instead of other, more appropriate ecological solutions. For example, ironically, a follow-up study in 1979 found that Banksula melones occurred in 18 caves in the area. Obviously, good faunal surveys of a karst area are needed before ever considering a questionable rescue effort.

The ultimate survival of a cave or karst community depends on the proper protection and management of the cave and the surrounding terrane. In the case of some endemic, terrestrial cave invertebrates, a one-hectare preserve may be sufficient as long as nutrient and water inputs are not altered and disturbances are minimal. However, often we must reach beyond the immediate karst area to contributing watersheds or, in the case of bats, to alternate roost habitats. With migratory bats, these considerations must be on a continental scale to insure success.

Many cave preserves that have been set aside only protect the entrance area, and not the entire watershed for the cave system. Many recognize the need for ecosystem management, which considers the whole karst area. The trend by governments has been toward increasing aspirations for karst ecosystem management, but in practice it is very difficult financially and politically. In the Austin, Texas, area, even though seven terrestrial troglobites have been listed as endangered, the federal government has not bought any cave preserves for them, even though it has spent millions of dollars to purchase a national wildlife refuge nearby for the benefit of two endangered bird species. Sixty-five cave preserves that were planned will have to await funding through a local development fee collected by the county and city (Elliott 1997c).

Some believe that caves cannot be managed, and that they should be left alone (except for occasional caving trips). Such a passive conservation ideal cannot work in developed areas where drainage patterns are changed, native vegetation and faunas are gradually perturbed, nutrient and moisture inputs are altered, and pests invade. In managing cave preserves, it is important to be able to measure the results from time to time. Therefore, baseline surveys, census surveys, and written management plans are essential.

Karst groundwater issues are so economically and politically important that they move beyond the influence of the technical experts who best understand them (Elliott 1994d, 1996b). In Texas, the regulation of overpumping of the Edwards Aquifer, one of the most important karst aquifers in North America, has been gradually improved only through a succession of state rulings and legislations that were contradicted by federal court decisions. It is quite possible that the San Marcos and Comal Springs will go dry within the next decade, endangering many species and the human economy (Elliott 1993a, 1996a).

In general, the most dramatic declines in cave faunas have been caused by the direct disturbance and killing of bats, and massive kills of aquatic troglobites from water projects, sewage, and chemicals. Perhaps five North American cave species became extinct as a result of human activities, and it is possible that other extinctions have occurred. Local extirpations of several species of bats, cavefishes, and crustaceans have been documented. However, the subtle and inexorable decline of some cave communities over decades may go unnoticed because of a lack of baseline surveys and systematic monitoring. Nutrient stress is a problem that few cave biologists have studied, but the long baselines in Mammoth Cave and Carlsbad Cavern have afforded us a few insights into this subtle process.

Although many cave management plans have been devised across North America, and 20 species are under protection, it is apparent that many other species are just as threatened by human activities. It is more obvious than ever that regional karst ecosystem management and protection strategies should be encouraged, while not forgetting to fund the small cave preserves that can protect locally endemic species with a minimum investment.

Table 34.1. Possibly extinct cave-dwelling species of North America.