Out of Sight, Out of Time: The Endangered Species Living Hundreds of Feet Beneath Austin

Pollution and the overdrawing of groundwater threaten to wipe out several species of subterranean salamanders.

July 11, 2019
A Barton Springs salamander

Thomas J. Devitt

No matter where you are, be it on top of a mountain or in the middle of a desert, groundwater is flowing beneath your feet. It moves through cavities and cracks in the bedrock, and porous layers of sandstone and limestone soak it up like an ancient sponge. In fact, though most of us never give it a second thought, there’s a thousand times more water underground than what’s found in all the rivers and lakes on the planet’s surface.

And where there’s groundwater, there’s life.

Take the Barton Springs salamander (Eurycea sosorum). These amphibians grow no longer than a baby-cut carrot, and instead of lungs, they have blood-red gills coming out of their heads that they use to breathe with—a feature crucial for their survival in habitats that can reach more than 300 feet belowground.

How do we know they live at such depths? Because scientists have dropped cameras down wells that descend into subterranean aquifers and seen the little slimers smiling back at them through the darkness.

“Talk about a needle in a haystack,” says Thomas Devitt, a biodiversity scientist at the University of Texas at Austin. “Keep in mind, this has only happened a handful of times.”

As you might imagine, studying animals that live this far belowground is really, really difficult—almost like deep-sea exploration. “Except even harder, because we can’t cruise around in a submarine in the aquifer,” says Devitt.

Recently, Devitt was part of a team that traveled to 99 different surface springs (where the salamanders also can live) and caves across Texas in an attempt to catalog the various salamander species of the Edwards-Trinity Aquifer system. This aquifer runs more than 200 miles from north of Austin to the Mexican border in western Texas and is considered to be one of the most species-rich groundwater systems in the world. Unfortunately, more than a dozen of the creatures that populate it, such as the Barton Springs salamander, are already endangered or threatened. One mosquitofish, known as the San Marcos gambusia, hasn’t been seen since 1983 and is presumed extinct.

Animals who live in aquifers aren’t free to roam around like their cousins up above. Their world is confined to a massive maze of rock formations below the surface. Over eons, flowing water has carved spaces in these subterranean layers. Limestone dissolves into Swiss cheese. Layers of sedimentary rock shift, rise, and fall, creating passageways and gaps.

Salamanders, catfish, crayfish, diving beetles, and other hardy organisms tend to move between these pockets only during high-water events. Afterward they become trapped, sometimes for thousands of years, during which they slowly evolve into new, slightly different species—species that, by nature, exist in only very small ranges and are therefore more susceptible to extinction.

The Barton Springs salamander is a prime example. It was known to exist in only four freshwater springs located in downtown Austin—each of which is connected to the same underground sources of water that about 60,000 people rely on for drinking water, brewing craft beers, and filling up a popular outdoor swimming place known as the Barton Springs Pool. Over-pumping of groundwater has lowered the water levels that the salamanders rely on, and real estate development in the rapidly expanding urban area has steadily added nitrogen and sediment to their habitat, threatening to poison its waters.

People swim in Austin’s Barton Springs Pool on a hot summer day.

Adam Gasson/Alamy

Concerned about the salamanders’ continued existence, the U.S. Fish and Wildlife Service listed it as endangered back in 1997. The FWS has yet to establish any critical habitat for the species, even though it is required to do so under the Endangered Species Act.

But there is some good news. Devitt’s study, published in Proceedings of the National Academy of Sciences earlier this year, found that the Barton Springs salamander is actually slightly more widespread than previously thought. Using genetic tests that weren’t available when the species was first listed, Devitt has discovered populations to the south and west of Austin. He thinks it’s unlikely that the new additions would have an impact on the species’ endangered status, but there could be implications for several other species.

For instance, the FWS is currently reviewing a petition to list a population of salamanders in Comal Springs, which is a few miles northeast of San Antonio, as a distinct species. But Devitt’s genetic tests reveal that these amphibians actually belong to the species Eurycea pterophila, which also occurs in the nearby Bear Creek Spring. At the same time, a species known as the Georgetown salamander seems to have a range more limited than previously thought—meaning it’s more endangered. Devitt’s team also provided evidence for the discovery of three new, genetically distinct species that have not yet been described by science. One of them, a gold-colored amphibian found west of Austin, would likely qualify for a critically endangered listing.

It may seem like splitting hairs, but figuring out these kinds of details that affect population counts is incredibly important for maintaining accurate listing statuses and ensuring we aren’t over- or underestimating any species’ risk of extinction. After all, salamanders gaining protections under the Endangered Species Act, even subterranean ones, can affect the rest of us up above. Especially in the Lone Star State.

“In a lot of parts of Texas, there’s a very sort of knee-jerk reaction to endangered species, and I think a lot of that stems from feelings about private property rights,” says Devitt. Groundwater is considered private property in Texas, and Texans place a high value on those rights, he explains. “So anytime an organization comes in and says you can’t use the groundwater like you used to, then people are going to get upset.”

In such debates, it’s important to remember that the same protections that the ESA affords salamanders or any other aquifer-dwelling species are actually good for people too. Cities like Austin need water just as much as the salamanders do, so making sure it isn’t drawn down to nothing or polluted by chemical spills or runoff from construction is every bit as important to Texans as it is to amphibians.

Many of the springs in Texas that flowed just 50 years ago now run dry. And with the current rate of increase in water demand and population growth, many of the species Devitt and his colleagues are hustling to simply discover and describe may well perish within the next century.

Also, aquifers are not inexhaustible resources, though it might sometimes seem that way. In some areas, Devitt says the Edwards-Trinity system has already been drawn down 200 to 300 feet.

“That’s not going to be replaced,” he says. “That water is gone.”

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