“Within karst landscapes…alteration of vegetative communities of any sort can lead to substantial and potentially irreversible impacts on the karst processes.”
Dr. Peter Ulrich (2002)
Karst Geologist and Managing Director CLIMsystems, Ltd.
Shallow, Rocky Soils
Karst country soils are very shallow and take four to ten times longer to rebuild than other soils because of the underlying limestone bedrock. As the limestone dissolves, it should add minerals to the subsoil. But on karst country this layer is either absent or not substantial, so most minerals get washed downwards into the bedrock.
Due to their longer recovery, is essential to keep karst country soils covered during managment and development operations. This is because Texas karst country is prone to gully-washing rains, droughts, and hot summers. Any exposed soil will easily degraded and wash away.
Unfortunately, our primary approach to land management has been to clear out mountain cedars and other so-called brush, that leaves soils vulnerable to erosion and dehydration. After decades of doing this, much of this region is moving towards rocky desertification.
We need a better solution…one that focuses on protecting the soil, because we have a SOIL, not a CEDAR, problem.
A History of Degradation
When this region was first settled by Europeans in the mid-1800s, the vegetation was described as a dynamic mosaic that was more than half wooded with the rest being open prairie. The forests were vast, the soils dark, wildlife abundant, and springs flowed year-round. Mountain Cedars (juniper trees that mostly grow on limestone karst country) grew dominated almost half the wooded areas and grew mostly as trees not bushes.
Not understanding the inherent fragility of karst country, European settlers repeatedly burned fields, clearcut hillsides, and overstocked prairies. In the 1890s, the region experienced a prolonged drought. Exposed karst country soils quickly degraded. When gully-washing rains returned with a vengeance, much soil was lost to erosion.
Since most Texas karst country could no longer supported dense grass and old-growth forests, pioneering, bushy thickets of Mountain Cedars began to grow where old-growth tree and grass cover was thrived. These thickets were protecting karst country soils from further harm.
Yet, in 1939, it was observed that where bushy thickets were removed, springs began to flow. People assumed this meant the trees were bad and so the effort to wipe them out began. In the 1940s, the government paid landowners to clear most of the spreading brush. Doing this led to another mass wave of erosion where we lost an average of 5 inches of topsoil. Although it was clear that continued clearing often led to soil loss, degradation, and flooding, landowners continued to clear out the woody brush since it provided a much-needed, short-term fix: more grass.
Almost 100 years later, science has proven these limestone junipers are part of the solution to regenerate the soils and limestone porosity of degraded karst country. Clearing them before the land has healed is like ripping off a cast before a bone can heal. For this reason, we need to learn to use them or mimic what they’re doing to more effectively regenerate these fragile lands. We need to stop focusing on a species of tree and instead focus on keeping the ground covered, slowing down stormwaters, and reviving soil biology.
Changing to nature-based solutions will not be easy, but will benefit us all.