Deep in the Karst of Texas

Deep-rooted Trees are Sucking the Landscape Dry in the Southwest, but Rob Jackson is Working to Find Solutions

by Michael Tennesen

The late-spring Texas temperature hovers near 100˚ F as Rob Jackson and Andrew McElrone descend a 35-foot ladder and drop into the mouth of Powell’s Cave.

Rumored to be where 19th-century frontiersman Jim Bowie once hid a load of silver, the cave is actually a labyrinth of three interconnected caves that stretches for more than 13 miles through the porous limestone bedrock of the Edwards Plateau, about 150 miles west of Austin.

Jackson is Nicholas Professor of Global Environmental Change and professor of biology at the Nicholas School. McElrone is a former postdoctoral research associate of his who is now a plant physiologist for the USDA.

They’ve been coming to Powell’s Cave in the dusty Hill Country of west central Texas for the past five years to measure changes taking place deep within its subterranean chambers—changes which, despite occurring far below ground, are having a profound impact on surfacedwelling species in the region.

At the end of the cave’s entrance ladder, the scientists disappear into a deep slot in the rock and, using headlamps to light their route, make their way down a steep, twisting path, past precipitous drop-offs and through a few tight crawl spaces, until they emerge into a large underground cavern, 60 feet beneath the surface, with a crystal-clear stream flowing at its base.

“That’s probably as clear a water as you’ll ever find,” Jackson points out.

His voice echoes off the walls, but he and McElrone aren’t the only visitors at the bottom of the cave. From out of its limestone walls and ceiling come a number of roots from juniper and mesquite trees high above. They poke their way out of tiny cracks and crevices in the rock and dip into the cool, clear subterranean stream for a drink.

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