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In a cluster of spring-fed ponds, surrounded by desert in southern Presidio County, a few dozen turtles nibble grass and rest in the cool mucky bottoms of their last known habitat in the United States. They don’t look particularly rare. Small and brown, the Chihuahuan Mud Turtle resembles another mud turtle that can be found in numerous stock tanks and ponds throughout the southwest. But the secluded pools off Alamito Creek are one of a handful of places in the world where a Chihuahuan Mud Turtle can be found.

Steven Platt, a Sul Ross State University zoologist studying these turtles, explains that Alamito Creek used to have flowing water, and the turtles probably lived in many places along its muddy banks and in the surrounding wetlands. But over the last century or so, the creek dried up and the wetlands disappeared with it. The only remaining places the turtles could find water were nearby stock tanks and spring-fed ponds. Since the turtles were first studied here in the 1980s, a few of those ponds and tanks have been drained, and the turtles probably got up and moved, or dried up and died.

Now the Chihuahuan Mud Turtle’s last known homes are a few places in Mexico and the cluster of ponds in Presidio County, where Platt has so far found about 30 turtles. Three of the ponds are connected and fed continually by a spring; the fourth pond’s water level seems stable, though Platt isn’t sure whether it’s replenished by rain or groundwater. For now, the ponds, being on private property, are protected, and Platt says the turtles’ existence there seems secure.

“Because the turtles are so dependent on these isolated wetlands, they’re really vulnerable,” he says. “If the springs dried up, the ponds would dry up probably. And that would be the end of those turtles.”

Over in Brewster County at Big Bend National Park, the Big Bend mosquito fish hangs on to an even more fragile existence in spring-fed ponds. These guppy-like fish, also called gambusia, feed on mosquito larvae and bare live young, which makes them unusual in the fish world. The native Big Bend gambusia were thought to be extinct in the early part of the 20 th century, after their only known habitat at Boquillas Spring went dry. But in the 1950s, they were rediscovered at a cluster of warm springs near Rio Grande Village.

“You could draw a quarter-mile-diameter circle around all of those fish and all of their habitat in the world,” says Raymond Skiles, a park wildlife biologist. “They would not make it without not just the springs, but the consistently warm water temperature.”

Even though their remaining habitat is protected, the invasion of exotic fish species still threatens the mosquito fish at Rio Grande Village. Without the assistance of pumps and mechanical devices to keep those exotics away, Skiles says the Big Bend mosquito fish would still be at risk of extinction.

These are not unusual stories in the Chihuahuan Desert. Many plants and animals here depend on spring-fed pools and puddles for water, and some species, like Hinckley’s columbine of southern Presidio County and the wild rose of Wild Rose Pass, can only be found at a few isolated wet spots in Far West Texas.

“Any place where you have springs emerging in the desert floor, not only are they crucial for wildlife, but there’s a very high likelihood that they have biota of conservation import—plants or animals that occur nowhere else or only in a few places on the planet,” says John Karges, the Nature Conservancy’s regional program manager. “It might be a crustacean or a mollusk or a plant that absolutely has to have its feet wet.”

Fortunately there is a litany of springs amid the high desert’s dry flatlands and mountainous folds. Social Disease, Know Nothing, Wildhorse, Burro and Boot are among several hundred spring names dotting the Far West Texas landscape, according to Gunnar Brune’s 1981 book Springs of Texas. Big Bend Ranch State Park claims about 130, and two of those feed the second and third highest waterfalls in Texas. Big Bend National Park hydrologist Jeff Bennett says about 300 water sources have been surveyed there. The Davis Mountains too are aspersed with springs and seeps. Some of these gush year-round, others flow seasonally; some scarcely trickle from a rocky cliff, and others are now dry.

Groundwater finds its way to the surface in several different ways. At springs around Balmorhea, it rises from cake-like layers between ancient sea-bed sediments. Further south in parts of Big Bend, it flows out through eroded igneous-rock cliffs, or is pushed up faults from pleats and pockets in underground volcanic formations. Wherever water emerges from this hidden topography and interrupts the arid landscape, a variety of plants and animals thrive.

Gently clapping leaves of pale-trunked cottonwoods and the showy sway of willows often divulge a spring’s location. These native trees, as well as exotic invasive salt cedars, are among Big Bend’s thirstier plant residents. Sul Ross greenhouse manager Patty Manning says clusters of sedges, Maidenhair ferns and the tall fluffy plumes of Deer Muhly grass are also commonly found at springs here.

These water-loving plants create islands of shade and shelter for many animals in an otherwise inhospitable environment, according to Skiles at Big Bend National Park. Besides hosting amphibians and aquatic invertebrates, spring habitats are essential for many of the region’s mammals – javelina, deer, foxes, bobcats, bats, raccoons, skunks and the myriad rodents at the base of the food chain. While these animals may not live at springs all the time, they never stray too far from these reliable water sources, Skiles says.

Migratory birds, like the Vermillion flycatcher and Black-capped vireo, also depend on these shaded, moist oases as safe places to stop and rejuvenate for the night, during their long and stressful passage across the desert.

“ Big Bend National Park is known for having a great diversity of bird life, and we can partly attribute that to the abundance of springs,” Skiles says. “If migrants can’t find one of these habitats with relative ease, they’re putting themselves in a vulnerable position.”

And, of course, humans too have gravitated to the Big Bend region’s springs. For prehistoric hunter gatherers, water was always the limiting factor as they wandered the parched landscape, explains John Seebach, an archeologist with Sul Ross’s Center for Big Bend Studies. Pictograph-lined rockshelters at the San Esteban springs south of Marfa, Las Cuevas Amarillas springs in Big Bend Ranch State Park, and Agua Fria springs northwest of Study Butte are just a few of the abundant archeological sites that indicate the region’s earliest inhabitants relied heavily on springs for water.

“Springs have always been a magnet for human occupation, especially in an environment like the Chihuahuan Desert,” Seebach says. “Springs also attract game animals and plant growth. Humans, of course, glom onto that fairly quickly.”

Folsom hunter-gatherers, who roamed the area hunting giant ice-age bison about 10,800 years ago, relied on springs at Van Horn Wells, where they would have also had access to good stands of wood and nearby stone quarries for tool-making. A millennia-long drought drove humans away from the region until about 4,000 years ago, but as modern-day climatic conditions set in, hunter gatherers returned here. Again, these Middle Archaic peoples depended on springs, seasonal creeks and rain-filled tinajas for water.

“Coming off that drought, water would have been a really precious commodity,” Seebach says. “We have every reason to suspect that these people knew of almost any available water and would just travel from water source to water source.”

Springs have determined the patterns of more recent human settlement here as well. Barrilla Springs near the junction of Reeves, Pecos and Jeff Davis counties, El Muerto Springs northeast of Valentine, Fort Davis Springs, Comanche Springs, Kokernot Springs and Paisano Springs are among several dozen watering holes that played a role in the region’s history, according to Brune’s book.

Some provided welcome campgrounds for early Spanish explorers and missionaries, Jumano Indians and other Native Americans, and later Anglo military expeditions and survey teams. Others helped shape paths of major thoroughfares, from the Old Spanish Trail and Chihuahua Trail, to the Butterfield Overland stage route and Southern Pacific railroad. Many Far West Texas forts and towns were situated at springs; Comanche Springs sustained Fort Stockton, and Kokernot supplied Murphyville, now Alpine.

But as humans have populated the region and tapped into the groundwater with wells, many springs have stopped flowing. At historic Fort Davis for example, a stand of towering cottonwoods is the only testament to waters that no longer reach the surface. Or the Balmorhea valley, which a few hundred years ago was kept lush and moist by one of the state’s largest spring networks.

“It was rich and bountiful,” says the Nature Conservancy’s Karges. “It was probably this braided marshland, with big cottonwoods over some of the open creek water, lots of marsh grasses and spring rivulets running through it.”

That water is now known to travel great distances before it reaches the valley, according to Sul Ross geologist Kevin Urbanczyk. Groundwater under Valentine flows west through the subsurface to Van Horn, then takes a turn east and emerges at San Solomon, Sandia, Griffin, Saragosa, Toyah, and Phantom springs around Balmorhea.

This mighty spring network has been diminished though over the last century. With agricultural development and occasional drought, the groundwater has been pumped faster than rainfall can replenish it. San Solomon is still the popular focal point of Balmorhea State Park and remains one of the five largest springs in Texas, Karges says.

But Phantom Spring, which emerges from a cave west of Balmorhea, no longer flows without assistance. A pump deep in the aquifer now squirts water out the cave’s mouth, providing life support to a unique group of creatures. Without that flowing water, a few rare types of snails and a rare crustacean would be wiped from the planet, and two species of endangered fish, the Comanche Springs pupfish and Pecos gambusia, would be closer to extinction.

These two tiny fish were once well represented in the Pecos River basin, but they were brought to the brink of extinction after a few springs around Fort Stockton went dry. Both Comanche Springs and Leon Springs failed on the heels of the 1950s drought and Clayton Williams Sr.’s landmark court case that established the right of capture.

“Now that population of Comanche Springs pupfish at Comanche Springs is gone. It’s extinct,” Karges says. “Fortunately they discovered another population of Comanche Springs pupfish in Balmorhea at the state park and at Phantom Spring.”

The Pecos gambusia also lives on at these springs, as well as another desert spring, Diamond Y, a few miles north of Fort Stockton. Now protected as a Nature Conservancy preserve, Diamond Y is what Karges calls a “West Texas Galapagos.”

“It’s not a very pretty place,” he says. “Water comes up through a fissure out into the middle of a big pool in the desert.”

But in and around that desert pool, where pump jacks and gas rigs line the horizon, many rare animals and plants are hanging on to a fragile existence. A few types of snails, a crustacean and crayfish, and the Leon Springs pupfish live nowhere else in the world. It’s also the only place the Pecos sunflower, or puzzle sunflower, can be found on the planet, and Karges says three even rarer plants live under the sunflower.

At Diamond Y preserve, as well as the state and national parks, the last footholds of Far West Texas’s most threatened spring-dependent plants and animals are protected, but not guaranteed. Continued groundwater pumping, drought, climate change and invasive species loom as threats to conservation efforts.

“What terrifies me is driving up to Diamond Y some day and finding out so many oil wells have gone in there that all of the sudden, the spring went down into the commode of the earth. Then we don’t have many options, because we’re very unlikely to get that spring to refill again,” Karges says. “That would mean imminent death and extinction for some pretty rare organisms.”

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