Knowledge is power: How can we make cave tourism more environmentally friendly?

A new study in Nature Conservation presents a literature-based dataset on the ecological status of 265 show caves in 39 countries across the world.

Throughout history, people have used caves for a number of reasons: as shelters, places for rituals, food storage, and, in more recent times, as touristic attractions.  In these so-called show caves, visitors can experience the natural beauty of caves, usually by following a guide on constructed, artificially lit trails.

But caves are also very fragile ecosystems, bursting with underground life. They are home to numerous invertebrate and bat species, including ones that are threatened or endemic. The human disturbances caused by the changes in the infrastructure and environment, coupled with the influx of tourists, often affect the ecological processes and, consequently, these organisms. But how much do we know about the influence of tourists on cave ecosystems?

According to a new study in the open-access journal Nature Conservation, not enough.

Apart from affecting subterranean invertebrates, the artificial lighting and noise related to tourist visits may also affect the life of bats, making it harder for them to reproduce or overwinter in caves.

Going through more than 1,000 scientific papers, an Italian team of scientists, led by Marco Isaia and Elena Piano from the University of Torino, prepared a literature-based dataset relative to the knowledge on the ecological status of 265 show caves in 39 countries across the world. Their database includes a georeferenced set of show caves, where researchers have evaluated a number of environmental indicators that help monitor the impact of tourism and its related activities on subterranean ecosystems. They also list cave characteristics for each cave, including its natural heritage that attracts tourists.

There are many ways in which tourism can disturb life in a cave. For example, the presence of visitors may help increase cave temperature, which, combined with the increase of CO2 air concentration caused by tourists’ breath, may enhance carbonate dissolution, damaging geological formations. Moreover, tourists can carry pollutants and propagules of microorganisms into the cave through their clothes and hands, which then land on geological formations, in the water, in the air, and on the ground. Apart from affecting subterranean invertebrates, the artificial lighting and noise related to tourist visits may also affect the life of bats, making it harder for them to reproduce or overwinter in caves.

The dataset published in Nature Conservation set a baseline towards the integrated and multidisciplinary study of the impacts caused by tourism on these fragile ecosystems, but the research team points out that much remains to be done. For example, they found out that there wasn’t enough research on show caves outside of Europe, or on the possible impacts of tourism on the subterranean fauna in the context of climate change.

Ultimately, the data in this study can help managing authorities come up with guidelines that will allow a sustainable touristic development of show caves, not only from an environmental perspective, but also from an economic and social point of view.

“Overall, this data paper could fill the lack of awareness towards the fragility of the natural heritage of show caves to favour a sustainable touristic use that would guarantee their preservation for future generations as well as the economic development of local communities”, the authors conclude.

Research article:

Piano E, Nicolosi G, Mammola S, Balestra V, Baroni B, Bellopede R, Cumino E, Muzzulini N, Piquet A, Isaia M (2022) A literature-based database of the natural heritage, the ecological status and tourism-related impacts in show caves worldwide. Nature Conservation 50: 159-174. https://doi.org/10.3897/natureconservation.50.80505

All images are from Bossea show cave in Italy, by Simone Marzocchi.

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Small, rare crayfish thought extinct is rediscovered in cave in Huntsville city limits

Dr. Matthew L. Niemiller’s team found individuals of the Shelta Cave Crayfish in 2019 and 2020 excursions into Shelta Cave – its only home.

HUNTSVILLE, Ala. (June 1, 2022) – A small, rare crayfish thought to be extinct for 30 years has been rediscovered in a cave in the City of Huntsville in northern Alabama by a team led by an assistant professor at The University of Alabama in Huntsville (UAH).

Dr. Matthew L. Niemiller’s team found individuals of the Shelta Cave Crayfish, known scientifically as Orconectes sheltae, in 2019 and 2020 excursions into Shelta Cave – its only home.

The Shelta Cave Crayfish is known to exist only in Shelta Cave. Courtesy Dr. Matthew L. Niemiller

Dr. Niemiller, an assistant professor of biological sciences at UAH, a part of the University of Alabama System, is co-author of a paper on the findings in the journal Subterranean Biology. Besides Dr. Niemiller, authors are UAH’s Katherine E. Dooley and K. Denise Kendall Niemiller, and Nathaniel Sturm of the University of Alabama.

The crayfish’s home is a 2,500-foot cave system that’s owned and managed by the National Speleological Society (NSS) and is unobtrusively located beneath the organization’s national headquarters in northwest Huntsville and is surrounded by subdivisions and bustling roadways.

Map of Shelta Cave showing the distribution of aquatic habitat during high water levels and the location of Shelta Cave Crayfish observations (black crayfish symbol) during the study. Map modified with permission of the Alabama Cave Survey.

“The crayfish is only a couple of inches long with diminutive pincers that are called chelae,” Dr. Niemiller says. “Interestingly, the crayfish has been known to cave biologists since the early 1960s but was not formally described until 1997 by the late Dr. John Cooper and his wife Martha.”

But the aquatic ecosystem, including the Shelta Cave Crayfish, crashed sometime in the early 1970s. The crash may be related to a gate that was built to keep people out of the cave and yet still allow a grey bat maternity population to still move freely in and out.

Even before the decline in the aquatic cave community, the Shelta Cave Crayfish was never common compared to the other two species, Southern Cave Crayfish (Orconectes australis) and Alabama Cave Crayfish (Cambarus jonesi).

“To the best of our knowledge, only 115 individuals had been confirmed from 1963 through 1975. Since then, only three have been confirmed – one in 1988 and the two individuals we report in 2019 and 2020,” Dr. Niemiller says.

“After a couple of decades of no confirmed sightings and the documented dramatic decline of other aquatic cave life at Shelta Cave, it was feared by some, including myself, that the crayfish might now be extinct.”

While it’s encouraging that the Shelta Cave Crayfish still persists, he says scientists still haven’t rediscovered other aquatic species that once lived in the cave system, such as the Alabama Cave Shrimp and Tennessee Cave Salamander. 

“The groundwater level in Shelta Cave is the result of water that works its way naturally through the rock layers above the cave – called epikarst – from the surface,” says Dr. Niemiller. “However, urbanization in the area above the cave system may have altered rates at which water infiltrates into the cave and also increased rates of pollutants, such as pesticides and heavy metals entering the cave system.”

The crayfish was rediscovered during an aquatic survey aimed toward documenting all life that encountered in the cave system.

“I really wasn’t expecting to find the Shelta Cave Crayfish. My students, colleagues and I had visited the cave on several occasions already leading up to the May 2019 trip,” Dr. Niemiller says. “We would be fortunate to see just a couple of Southern Cavefish and Southern Cave Crayfish during a survey.”

Dr. Matthew L. Niemiller snorkels in Shelta Cave, where a species of crayfish believed to be extinct was rediscovered. Photo by Amata Hinkle

While snorkeling in about 15 feet of water in North Lake located in the Jones Hall section of the cave, Dr. Niemiller spotted a smaller-sized cave crayfish below him.

“As I dove and got closer, I noticed that the chelae, or pincers, were quite thin and elongated compared to other crayfish we had seen in the cave,” he says. “I was fortunate to swoop up the crayfish with my net and returned to the bank.”

“The second Shelta Cave Crayfish that we encountered was in August 2020 in the West Lake area,” he says.

The team had searched much of the area and didn’t see much aquatic life. As they started to make their way out the lake passage to return to the surface, Nate Sturm, a master’s student in biology at the University of Alabama who had accompanied the lab for the trip, noticed a small white crayfish in an area that the team had previously walked through.

To aid identification, the team analyzed short fragments of mitochondrial DNA in the tissue samples collected.

“We compared the newly generated DNA sequences with sequences already available for other crayfish species in the region,” Dr Niemiller says. “A challenge we faced was that no DNA sequences existed prior to our study for the Shelta Cave Crayfish, so it was a bit of a process of elimination, so to speak.”

Outside of the dissertation work done by Dr. Cooper, little about the life history and ecology of the species is known.

 “Groundwater is critically important not just for the organisms that live in groundwater ecosystems, but for human society for drinking water, agriculture, etc.,” Dr. Niemiller says.

“The organisms that live in groundwater provide important benefits, such as water purification and biodegradation,” he says. “They also can act like ‘canaries in the coal mine,’ indicators of overall groundwater and ecosystem health.” 

Research article:

Dooley KE, Niemiller KDK, Sturm N, Niemiller ML (2022) Rediscovery and phylogenetic analysis of the Shelta Cave Crayfish (Orconectes sheltae Cooper & Cooper, 1997), a decapod (Decapoda, Cambaridae) endemic to Shelta Cave in northern Alabama, USA. Subterranean Biology 43: 11-31. https://doi.org/10.3897/subtbiol.43.79993

About The University of Alabama in Huntsville

Launched from America’s quest to conquer space, The University of Alabama in Huntsville is one of America’s premier doctoral-granting, research-intensive universities. Located in the second largest research park in the United States, UAH has robust capabilities in astrophysics, cybersecurity, data analytics, logistics and supply chain management, optical systems and engineering, reliability and failure analysis, rotorcraft and unmanned systems, severe weather, space propulsion and more. UAH prepares students for demanding positions in engineering, the sciences, business, nursing, education, the arts, humanities and social sciences.

Read the full press release by The University of Alabama in Huntsville.

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Cave fights for food: voracious spiders vs assassin bugs

Killing and eating of potential competitors has rarely been documented in the zoological literature, even though this type of interaction can affect population dynamics. In a recent publication in the open-access journal Subterranean Biology, Brazilian scientists presented their notes regarding the predation of an assassin bug by a spider in Neotropical caves. Underground, where food resources are scarce, such events might be possible as a result of ecological pressures imposed by the hostile environment, hypothesise the researchers.

Killing and eating of potential competitors, also known as intraguild predation, is a rare event that occurs only in specific situations such as severe scarcity of food resources, resulting in the competition between predators.

A recent paper in the open-access journal Subterranean Biology examines the case of a wandering spider species (Enoploctenus cyclotorax) seen to prey upon assassin bugs (Zelurus diasi) in a limestone cave in Brazil.

Even though such type of ecological interaction is uncommon, it is potentially important since it may decrease the competition between apex predators and thus, affect their population dynamics. Zelurus and Enoploctenus are voracious predators with a wide distribution in caves and epigean environment. Both of them have similar diets. In normal conditions, spiders reject assassin bugs as potential prey, so intraguild predation cases occur only in very specific situations.

From the perspective of the participants, intraguild predation is a dangerous strategy because the prey is also a predator, armed and capable to kill. However, in caves, this could be a very useful behaviour since food resources are scarce and have low density.

“This may be an important factor, maintaining the species in that challenging environment”, concludes lead author of the study Dr. Leopoldo Ferreira de Oliveira Bernardi.

The scientists suggest that probably prey scarcity has left little choice for spiders, and that’s why they ended up using unconventional type of prey in their diet.


Intraguild predation between female Enoploctenus cyclotorax and adult Zelurus diasi observed during the study.
Credit: Leopoldo Ferreira de Oliveira Bernardi
License: CC-BY 4.0

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Original source:

Bernardi LFO, Sperandei VF, Audino LD, Sena CH, Alves JA (2020) Notes on the predation of an assassin bug by a spider in a Neotropical cave. Subterranean Biology 33: 17-22. https://doi.org/10.3897/subtbiol.33.48292