On a remote wooded hillside in the southern Missouri Ozarks, Tom and Cathy Aley have built a big stone-and-timber house. beneath the hill they have another home, made by nature: the two-mile-long Tumbling Creek Cave. "Quite a view, isn't it?" Tom said one night, sweeping a headlamp across the Big Room -- a 60-foot-high chamber graced with giant crystalline formations and a rushing creek that echoed deafeningly off the walls 170 feet below the ground. Besides the nice interior scenery, Tumbling Creek has biological wonders. It is host to 115 species of animals, the richest assemblage of fauna in a single cave west of the Mississippi -- dozens of rare subterranean creatures such as blind salamanders, bats including endangered grays and Indianas, the endangered Tumbling Creek cavesnail (pop. 50–150; known to exist only here), and the unique blind cave millipede Chaetaspis aleyorum, a fingernail-length string of pearls that loves bat guano.
"It's a myth that rock is solid," said the 68-year-old Aley, who is always quick with a corny joke. Aley, a pioneering hydrologist and expert on all things subterranean, and his wife, Cathy, an aquatic biologist, have spent decades defending this cave and others from danger. "Caves are not worlds unto themselves," he said. "If you do something on the surface, it affects the underground." His studies of how water travels underground have shown how caves from Alaska to Arkansas suffer from surface pollution. While landowners typically run the other way from endangered species, Aley has found his own and spent a fortune -- made from his consulting work -- protecting them.
"If there is any one person who is the overarching protector of caves and karst in the United States, it is Tom Aley," says Ron Kerbo, a geologist who oversaw the National Park Service's caves until his retirement earlier this year. "Too many conservationists get overwhelmed by emotion. Tom operates on science. Because of him, a lot of people now see caves as part of the larger world."
Karst, a cave-rich terrain that develops in water-soluble rocks such as marble or dolomite, underlies 15 percent of the earth's surface; to a lesser extent, caves can also form inside volcanic or sedimentary rocks. Aside from their beauty and the priceless resources they offer geologists, archeologists, paleontologists, and other scientists, caves form a vast, little-known biological world. They are habitat for many part-time residents such as bats, which in turn play a large role in the ecology of the surface. In the United States, caves are also home to about 1,800 known species of troglobite -- creatures that dwell strictly in caves. These are primarily small invertebrates, plus some salamanders and fish. Most troglobites are elusive, even in well-explored caves, and 90 percent of the world's caves probably have yet to be found. So it's likely that the great majority of troglobites remain undiscovered.
They are also very vulnerable. More and more, roads, quarries, and building excavations are wiping out caves directly. For instance, nearly all the extensive karst that once underlay what is now St. Louis is badly damaged. Sewage, pesticides, toxic wastes, and fertilizers wash into sinkholes or other portals to the underground, unfiltered by soil. This turns underground streams into sewer conduits. It is not just the troglobites that suffer; in karst areas, these streams routinely feed back into human drinking water. Troglobites favor limited ranges of temperature, water chemistry, and humidity. Many are endemic to one cave, or one room of one cave, and are ill-equipped to survive elsewhere. A single disturbance -- say, a chemical spill on a nearby highway -- can kill a whole species. Only about 2 percent of the species in the United States are actually listed by the government as endangered or threatened, but according to The Nature Conservancy, 95 percent are in fact imperiled. These include Hawaii's six-inch-wide Kauai cave wolf spider, which dwells in volcanic caves over which new golf courses are booming, and dozens of aquatic species in Texas's vast Edwards Aquifer, which is being quickly pumped dry to feed cities and farms. Bill Elliott, a cave conservation expert with the Missouri Department of Conservation, says at least six U.S. species are already presumed extinct, but he suspects there are many more.
Tom Aley was born in 1938 and spent his childhood in rural Wintersville, Ohio, building forts in the woods and reading biology books in the library. Long before studies of underground toxic waste became a big business, a shrewd practical streak told him that hydrology -- the then-fledgling study of water and where it goes -- would soon be important. At the University of California, Berkeley, he studied forestry, which involves hydrology -- and hydrology often involves karst. It was during his time at Berkeley that he visited his first cave, on a campus hiking-club trip. The dreadfully skinny six-foot-three Aley soon discovered that he loved descending into black pits and squeezing his head through any space that did not rip off his ears. Some weekends, he practiced in the Berkeley storm-sewer system. ("Best to wait for low tide and watch for cops," he remembers.) He went on to help discover about 40 new caves, from California to Arizona. One morning near the Grand Canyon, an earthquake shook him and some friends while they were deep inside a cavern. Everyone except Aley wanted to rush back to see if the entrance had collapsed. He argued that if it had, they were doomed; why not enjoy exploring the cave for the rest of the day, then find out at the end? They reached the intact entry just in time for sunset.
Around the time of the 1962 Cuban missile crisis, the U.S. Office of Naval Research wanted to know if Fidel Castro might have any caves good for hiding nuclear bombs; Aley wangled a grant from the agency to spend three carefree months exploring caves in Jamaica, Haiti, and the Dominican Republic, the closest ones to Cuba he could think of. After this, more consulting work came in, such as a plum job to explore and map a northern California cave that the owners wanted to turn into a tourist attraction. He was having so much fun, he never bothered finishing his Ph.D.