At some point, as I moved up from Death Valley to the high deserts in southern Utah, I began to notice that the dirt had become crusty, like what I’m used to on the snow in Michigan. A subtle thing. Curious. Eventually, I learned that this phenomenon is, to paraphrase Ranger Chris, what all life in the region depends upon.
Ladies and gentlemen, this is the cryptobiotic soil crust, and it occurs in the four states that are part of the Colorado Plateau—a huge hunk of real estate that uplifted, oh, a long, long time ago. Not only is this soil crust critical to life in the region, but it’s also imperiled.
Here’s how it works: Arid places, like these high deserts, tend to have loose sand blowing around. But in these deserts an incredibly ancient and useful organism—cyanobacteria—is impregnated in the dirt, and when it gets a little moist (rare in the desert) it becomes all happy and sticky. It begins to grow and to wrap its long, slimy fingers (filaments) around those loose sand granules, creating a tangle of filament and granule and binding the whole mess together. Even dried-out filaments still retain their death grip on the sand.
Then fungi and lichen and algae and mold get in on the act, and slowly, over decades, Voilà! crusty, cryptobiotic soil. But the beneficial effects don’t end there. Cyanobacterial crusts hold onto water and add nitrogen to the crust, so they make the soil more fertile (a big deal when “soil” is a bunch of loose dust). I came to appreciate the beauty of such a process during two days of wind that blew dust all over kingdom come. Without the crust, the whole desert would have been a dust storm.
But the worm in the apple (you knew this was coming) is that these soil crusts are fragile. I can attest to that, having tromped on them before I knew better. Once you break the crust, either by foot or by tire, you’re back to loose sand. Dry, easily eroded, and much less fertile.
Not only that, those beneficial organisms take a long time to reestablish. At least 20 years after one of my misplaced footprints for the cyanobacteria; 45 years for the lichen; and 250 years for moss!
While the national parks are able to do a good job of protecting the soil crusts by prohibiting off-road vehicles, buying out grazing leases, and educating visitors (“Don’t bust the crust” is the tagline), the parks are a small part of the overall picture.
On vast tracts of federal land, no such protection exists. I camped on BLM land and saw the dirt bikers, being the young rebels that they are, who felt no compunction about zipping anywhere they pleased. Signs that prohibited entry were simply broken off. Cattle had no respect for the crust, either, and they meandered all over the place.
The result? According to this website, “…disturbed crusts now cover vast areas in the western United States as a result of ever-increasing recreational and commercial uses of these semi-arid and arid areas. … the tremendous land area currently affected by human activity may lead to significant increases in regional and global wind erosion rates.”
I don’t mind telling you that I feel darned guilty for my part in contributing to the bad karma. I guess leaving only footprints is sometimes still too much.