When the Crickets Go Quiet: Why MoPac Expansion Threatens Caves, Critters & Barton Springs

Protecting caves is necessary for keeping Barton Springs healthy and flowing. That’s because the water that travels through these caves flows directly into the springs. But how do scientists determine if a cave is in good condition? One way is to look for the crickets!
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In Austin, two keystone species of cave crickets--Ceuthophilus secretus and Ceuthophilus sp. B. serve as keystone species, which means they act as a “health check” for cave ecosystems. When their numbers drop, it’s often a warning sign that something is going wrong.

Researchers monitor how many crickets come out of cave entrances during the first two hours after sunset. These numbers fluctuate depending on moisture, temperature, and other conditions. For instance, on cooler nights, fewer crickets may appear. That’s why scientists look for long-term trends, not just one-night changes. If, after accounting for weather and other natural factors, the number of crickets keeps dropping over time, it’s a warning sign that something might be wrong with the cave environment and for our groundwater.

Because cave systems are sensitive to surface conditions, a decline in cave cricket populations often signals environmental stress such as pollution, drought, habitat destruction, or harmful chemicals reaching groundwater. Cave crickets thus provide an early warning that human health could be at risk from polluted groundwater sources. By keeping an eye on these tiny but telling cave dwellers, we can get an early heads-up about the health of our caves and the springs that they help protect.

How Highways Put Our Caves at Risk.

Much of Austin is located atop porous karst limestone, which features caves and sinkholes necessary for recharging the Edwards Aquifer. Between the 1950s and 1990s, volunteer cavers identified and excavated about 200 caves in the Austin area, but since then, almost 20 percent have been filled in or paved over by developers who believed getting rid of caves made properties more marketable.

The Barton Springs segment of the Edwards Aquifer is recharged primarily through caves, sinkholes, and fractured creek beds. Dye-trace studies show stormwater entering local recharge features can reach Barton Springs in a matter of days. This karst landscape allows rainwater to quickly seep through faults and openings in the limestone, which replenishes the aquifer. When these caves and sinkholes are properly protected, the aquifer can supply steady flows of clean, fresh water to Barton Springs and Lady Bird Lake.

The flip side of quick recharge is quick contamination. Caves are an important gateway to the underground. Because the rainwater moves swiftly through these caves, the limestone aquifer lacks natural filtration of pollutants. In practice, this means “what goes in, must come out.” Any pollutants on the surface—from highways and urban development—rush into these caves and emerge into wells and springs, virtually untreated. 

Paved surfaces (roads) can reroute drainage, causing either too little water (drying out of the cave) or too much runoff (flooding it with polluted water). If the land around these caves is developed and polluted, the caves act like drains, funneling dirty water directly into the aquifer. When it rains heavily, the first rush of water flowing off the land picks up a lot of pollution—dirt, fertilizers, and bacteria. This polluted water quickly enters nearby caves. So, whatever pollution is on the surface ends up in Barton Springs within hours to days. 

Driskill Cave, located on US 290 near the Burger Center in South Austin (Source: Nico Hauwert, Ph.D. Texas Professional Hydrogeologist)

Highways are one of those places where harmful substances collect – oil, gasoline, and heavy metals. These pollutants, along with loose soil from construction sites, can easily find their way into the aquifer and downstream Barton Springs through exposed caves or nearby caves. 

The Driskill Cave, located on US290, near the Burger Center, in South Austin is a good example of how highways kill caves. 

Driskill Cave was once home to a variety of creatures, including an abundant population of cave crickets. Following the construction of U.S.290, however, polluted highway runoff proved lethal to the sensitive cave crickets, whose populations plummeted in a short span of time. The collapse of its cave cricket population stands as a clear warning sign for future highway projects—like the proposed MoPac South expansion.

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Austin’s Mopac South Corridor runs along the edge of the Edwards Aquifer recharge zone, and the plans to expand it have raised environmental concerns. Other projects in the area, such as the MoPac Intersections Project and SH 45 SW uncovered numerous previously undocumented caves, leading to construction delays and significant environmental risks. For example, circa 2019, as crews worked on an overpass at La Crosse Avenue, at least 72 caves, sinkholes, and voids were discovered in the construction area. This delayed construction significantly, while putting at risk Austin’s underground ecosystems and groundwater.

What happens when these caves are found during construction? They get paved over. This causes complete habitat loss. Paving over caves starves them of air and water and permanently changes their temperature and humidity beyond ranges that species can tolerate. 
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Let’s Do Better with MoPac South: Save Our Caves
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Protecting Austin’s cave ecosystems isn’t just about saving wildlife—it’s about protecting the natural systems that deliver safe, clean groundwater to everyone who depends on it for drinking water, as well as the flow to Barton Springs and Lady Bird Lake. Highways, including past expansions, have been a major source of cave destruction and contamination in our region. With the proposed MoPac South expansion, these risks are more serious than ever. The caves along its path are direct lines to Barton Springs. If we don’t prioritize the health of our caves, we could see increased pollution in Barton Springs and jeopardize the unique species, like the Barton Springs and Austin Blind Salamanders, that depend on the springs, and our iconic cave crickets, that rely on these delicate underground environments.

Take Action: Help Us Protect Austin’s Caves!

Donate to Save Our Springs today. Your contribution will help us hire the experts needed to challenge the MoPac South expansion and safeguard Austin’s caves, our crickets, and the clean water we all rely on. Together, we can stand up for Barton Springs, Lady Bird Lake, and the future of our community.

Sources/More Information about Caves and the Edwards Aquifer:

Karst and Recharge in the Barton Springs Segment of the Edwards Aquifer: Field Trip to the City of Austin’s Water Quality, Dr. Nico Hauwert and David Johns (2015)
Cave Cricket Exit Counts: Environmental Influences and Duration of Surveys, Floyd W. Weckerly (2012)
Barton Springs segment of the Edwards (Balcones Fault Zone) Aquifer, central Texas, Brian B. Hunt and Brian A. Smith
Wildland Caves, Austin Water Utility
Karst Invertebrate Habitat Requirements, U.S. Fish & Wildlife Services
Holes Delay MoPac Project, Phil Jankowski, Austin-American Statesman

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