A Desert Without Crusts Is a Desert Without a Skin

Suggested Citation: Kerr, Andy. 2000. Oregon Desert Guide: 70 Hikes. Seattle: The Mountaineers Books. pp. 48-49.

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Some things are easy to miss in the desert. Sometimes it is because you're not looking; other times it is because it is not there—or if there, just barely. Such can be the case with microbiotic crusts. Scientists first called them cryptogamic (literally "hidden reproductive organs") crusts, then cryptobiotic crusts. Let's just call them desert crusts.

Desert crusts are fibrous mats of interwoven lichens, fungi, and algae. A hundred tiny plant species may occur in the crust, along with thousands of species of bacteria and other organisms. Desert crusts usually look rather brown and dull, but they are nonetheless an essential part of healthy desert ecosystems (douse a patch with saliva and watch it turn bright green).

You may have noticed these crusts if you've looked under a big sage or in a crevice that a livestock's hoof, hiker's boot, or vehicle's tire couldn't get to. Less than 5 percent of the desert's original skin remains intact, mostly in large areas that haven't been destroyed by livestock hooves, vehicle tires, and hikers' boots. "The Island" in the proposed Deschutes Canyon Wilderness, the proposed Boardman Grasslands National Wildlife Refuge, and the Hanford Arid Lands Ecology Reserve in Washington are some of the more pristine examples of remaining desert crust. In natural conditions, desert crusts may cover 80 percent of the ground, with grasses and shrubs towering above on the rest. That this is still true in the Oregon Desert is evidence both that bison were never common here and that native ungulates more gently trod the land than the alien invaders of the same order. When desert crust is disturbed, recovery begins immediately, but it may take a century to fully recover.

Desert crusts:

• Enhance soil productivity. Crusts include cyanobacteria, tiny one-celled organisms that fix nitrogen from the air and leak it into the soil as an essential ingredient in plant growth. Resist erosion. An area of crustless desert can have ten times the erosion.

• Retain water. Crusts are a natural sponge that retain water after brief desert rains.

• Resist exotic species. Invasive species like cheatgrass can't get established in a well-crusted desert.

• Reduce the harmful effects of wildfires. Bare ground favors cheatgrass, which grows rapidly in the spring and then quickly dries into fuel for fires. In Idaho, land managers are seeding recent cheatgrass burns with native bunchgrass and then excluding livestock. This allows the bunchgrass and eventually the crust—to return. Fires in native bunchgrass and crust-covered sites are both less frequent and less intense.

A good crust is not hard to find, if you know where to look. Fortuitous confusion by BLM range managers makes a fine stand of desert crust highway close. Between Hampton and Riley, US 20 is the practical dividing line between the Prineville and Burns Districts of the BLM. Two fences bound the respective cattle allotments, leaving a triangle where the Prineville fence went to the highway, but the Burns fence is somewhat back from the highway on the other side. The result is a lucky triangle that has been cow-free for decades. Continued evidence of lack of interdistrict cooperation is that each has erected highway boundary signs, which are 1/2 mile apart, even though they could have shared the same post. Look for the back of the Prineville District sign (when traveling west, milepost 82.1) or the back of the Burns District sign (when traveling east, milepost 83.4).You're in the lucky triangle bounded by highway (mileposts 80.9 to 83.4) on the north and fence on the south. Park safely at a road to the south at milepost 81.7 and take a little stroll. Stay off the delicate crusts, which can't distinguish a cow hoof from a shoe sole.