The Desert's Fragile Skin - Brief Article

National Wildlife, Oct-Nov, 1999

History buffs may be thrilled to learn that tank tracks from training maneuvers supervised by General George S. Patton in 1940 still are visible in California's Mojave Desert. But the marks are alarming to ecologists. That's because healthy deserts are covered with living skins of cyanobacteria (below), lichens, algae, mosses and fungi that anchor grains of sand, capture moisture and fix nitrogen that nourishes vegetation. The crust is easily broken by boots, motorcycles, recreational vehicles and cattle .

Plenty of persistent marks from such activities exist, but the tank tracks are so remote researchers can be reasonably sure no one has driven on them since 1940. In a new analysis, ecologist Jayne Belnap of the U.S. Geological Survey estimates the track damage may take more than 1,000 years to recover fully. She points out, "Tracks in continuous strips, such as those produced by vehicles or bicycles, are especially damaging, creating areas highly vulnerable to wind and water erosion."

Other research has found that even desert rock can be protected by a sort of crust. Scientists from Sam Houston State University in Texas recently found that bacterial communities spread a gluey substance over sandstone, shielding the crumbly rock from wind and rain. As people increasingly are attracted to the Intermountain West and the Southwest, what's left of the fragile crust is very much at risk. Still, this is one environmental threat with a simple solution. As Canyonlands National Park advises, "Don't bust the crust." On both desert surfaces and sandstone, people can avoid causing further damage by staying on roads and marked trails.