The Desert’s Fragile Skin Can’t Take Much More Heat

Rebecca Finger-Higgens is hopscotching on copper-toned sandstone to avoid stepping on the desert's black, burnt-looking crust.

The top layer of the desert is made of biotic soil. The desert's skin is home to a whole community of organisms that are vital to the environment. Without the desert's skin, the lands would not have much life, flowers would not grow and shrubs would not survive.

The biocrust is a dark, bumpy surface that stretches between shrubs, like snakeweed and yucca, and the towering buttes and mesas that make up the Colorado Plateau. Finger-Higgens puts metal pin flags into square grids that cover 12 football-field-sized plots of land.

She is part of an ongoing study that has tracked the health of biocrusts since 1996. The desert's scruffy top layer was seen as a static feature of the ecology until the past few decades. The importance of biocrusts in sustaining the life and integrity of the desert has only recently been understood.

Matthew Bowker is an associate professor at Northern Arizona University and was not involved in the research.

No cattle have grazed on the land, and bikers and hikers are not allowed. There is a distinction. ATVs roar out of town and through the landscape, usually on designated roads, but sometimes swerving off-piste and into the desert. Hikers walk through the land in boots. The desert's reputation is harsh, but it is also a landscape where life is on the edge.

Scientists refer to biocrusts as living skin because the first organisms to take up residence are cyanobacteria, which under a microscope look like little worms that glide through the soil, leaving a trail of sticky fibers in their wake. The spongelike structure that absorbs water when it rains is created by soil particles. Soon moss, algae, fungi, and lichens move in as tenants. It can take a long time for this community to form a thick, knobby crust.

The strength of the wind can be a factor in the resistance of the microbes in the crust. They are vulnerable to compressional forces, such as a human foot punching through the crust, which can leave sun-loving cyanobacteria, lichens, and mosses buried with no light.