Dispatch by Nina Finley
Have you ever walked over dry dirt and noticed a crunch? Welcome to biocrust, a seldom-noticed layer of soil organisms living on the surface of arid lands. To the untrained eye, a biocrust might look like nothing more than a dark stain on the earth, but look closer, and you’ll see the orange circles of lichen, the gray-green carpet of moss, and the spidery filaments of cyanobacteria. Like a new subdivision constructed on bulldozed land, a disturbed biocrust repopulates in predictable ways after a soil disturbance. The earliest resident to move in, cyanobacteria, creates a bumpy substrate on which lichens and mosses can follow.
On Tuesday, September 27, dozens of crunchy-dirt enthusiasts convened in downtown Moab, Utah at Biocrust 3, the third International Workshop on Biological Soil Crust. The theme for the day: climate change. Global experts presented their findings. One study showed that mosses die when watered more frequently in summer. Another monitored the breath of biocrust, its exhale of carbon in dry times and inhale after a rain. A third considered albedo, or reflectance capacity, and found that bare ground reflects more light and heat back to the atmosphere than dark biocrust. The researcher pointed to a potential negative feedback cycle wherein climate change kills biocrusts, and the lightening ground acts as a natural brake on further warming.
“But don’t take this to mean you should go out there and bust the crust!” he warned. Climate-change mitigation is only one ecosystem service to consider. Biocrusts may not cool the earth, but they hold down dust in the wind, promote soil fertility by remaining active when vascular plants cannot, and retain water for longer than bare ground. You can think of biocrust as a civil servant. Much of the 630 million federal acres in the American West is arid and, therefore, crusted. To modify the Forest Service’s slogan: “The is your biocrust.” It belongs to the American people, and it’s up to us to decide how to manage it.
Right now, biocrusts are languishing under foot, wheel, and hoof. Once trampled, they can take centuries to recover. Add drier droughts and shorter, more frequent bursts of rain predicted for the Colorado Plateau in the coming decades, and the future of our public lands looks less than crusty. Biocrusts may reduce albedo, but what the planet needs most in an era of climate change is not a shiny white surface of bare dirt to reflect the sun, but a functioning layer of live soil with sufficient diversity to adapt. Next time you hear that crunch in your step, take a closer look and discover the millimeter-high forest of organisms breathing carbon and eating sunlight all around you. Better yet, stay on the trail, and admire your biocrust before you make it go crunch.