An underground movement

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Who will speak for the imperiled troglobites? Charismatic megafauna, they are not. Troglobites – not to be confused with troglodytes (cavemen) or trilobites (extinct arthropods) – are neither warm-blooded nor fuzzy. Most are invertebrates, including insects and crustaceans, but there are also troglobitic fish and amphibians – and all are as weird as they are rare.

Living in natural underground chambers, many species are endemic to just one cave, or even to one part of a single cave. Specially adapted to the absence of light, they are often sightless and colorless, even transparent. So no wonder there's still no Save the Whale-type initiative for these sometimes slimy, slithering creatures, which include a blind catfish found only in the Aigamas Cave in Namibia; the 30-cm-long, Venezuelan Scolopendra centipede, which can eat a bat whole; and a tiny, southwestern US cave-dwelling pseudoscorpion, with venomous claws. True, Slovenia – eager for tourism revenues – has encouraged a kind of cult around the endangered Proteus anguinus, a blind cave salamander popularly known as the olm or “human fish”. But for the most part, these critters, with faces only a mother troglobite could love, have lived for millennia out of sight and out of mind.

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That's a shame, for the following reason: stuck in one small place as they are, troglobites are super-sensitive and telling signposts for the health of a given environment. Many absorb pollutants such as pesticides and sewage, suffer inordinately from droughts, and are defenseless against invasive species. The threats to troglobites may not be as obvious or as dramatic as those faced by pandas and tigers – no one hunts them for their pelts or ships them off to zoos, to be admired. Yet considering what they portend for our own species, we should probably be paying them more attention. “About 25% of people around the world rely on drinking water from underground sources”, points out Arkansas cave biologist Michael Slay. “So understanding and protecting the species in caves ultimately means we're protecting ourselves.”

Scientists have recently been accumulating more data, both on troglobites and the mounting odds against them. Armed with the latest technology, researchers have been wriggling their way into the Earth's most elusive corners, including caves that have been sealed for millions of years. Between 1980 and 2005, for example, the rate of discovery of previously unrecognized underground fish species quadrupled, in comparison with findings from the preceding 60 years. To date, some 7500 species of troglobites have been identified, but researchers assume that many more species remain unknown to science. The race is on to find and describe these species in time to save them. “Once educated about troglobites, people may appreciate their special place in the world”, says University of Texas–Austin biologist Jean Krejca, hired a few years ago by California's Sequoia and Kings Canyon National Parks to survey subterranean life in that region.

The Nature Conservancy (TNC) estimates that 95% of US troglobite species are at risk of extinction. That's because they're so geographically restricted that nearby human development (eg a single new strip mall) could conceivably wipe out multiple species at a time. But Krejca and other troglobite fans are heartened by watching the trickle of species make their way onto Federal protected lists. In December 2009, for instance, the US government announced there was “substantial” information indicating that a designation of “threatened” or “endangered” may be warranted for 11 species of troglobites found in southwestern caves. “The fact that they're being listed, even though they aren't as cute and cuddly as the polar bear, means we're recognizing their value”, suggests Slay.

I see some marketing potential here. After all, a company called Giant Microbes has been selling plush toys representing viruses. Why not a blind cave-fish? While waiting for their close-up, however, troglobites may be able to count on people's enduring fascination with their mysterious habitats. At least a dozen US groups have sprung up in recent years, dedicated to preserving karst regions, the general name for the caves and tunnels formed when water percolates through the Earth's crust, dissolving rocks such as limestone and dolomite. According to the new Atlas of Global Conservation (on which I worked as a writer), available this month from TNC, karst terrain occupies nearly 15% of the Earth's surface.

In the Ozark Mountains region of the Central US, an ad hoc coalition of conservationists, landowners, and public officials is working to protect sensitive karst habitats by improving groundwater quality, regulating disposal of hazardous materials, conducting volunteer cleanups, and restricting access to important cave sites. “Karst landscapes are phenomenally beautiful”, remarks Slay, who works with TNC's Ozarks Karst Program.

Troglobites are famous for their patience. They have extraordinarily slow metabolisms – some can survive for years without eating and some live longer than humans. The big question, of course, is whether they can persist long enough for us humans to learn to appreciate their hidden charms.

Ancillary