The desert gets a biocrust skin graft
Without its cover of living microorganisms, the desert is eroding.
When Patrick Cruz’s ancestors carved honeycombed dwellings into the canyons of what’s now New Mexico’s Bandelier National Monument, the land looked very different than it does today. Biocrusts — communities of mosses, lichens and cyanobacteria — formed a living skin over the earth, anchoring it in place, storing water and carbon, and laying the foundation for ponderosa and piñon pine forests.
After drought drove the Ancestral Puebloans away from Bandelier and into nearby pueblos in the 16th century, European colonizers moved in. Their logging and livestock grazing devastated Bandelier’s biocrusts. Drought and bark beetles in the mid-20th and early-21st centuries then killed up to 90% of pines, leaving unshaded patches of dirt between juniper shrubs where little could grow. Together, these impacts now cause an astonishing 8,900 pounds of soil per acre to erode each year.
Similar erosion is on the rise across the Southwest as oil and gas drilling, recreation and new development tear up biocrusts. For Cruz, an archaeologist and tribal member of Ohkay Owingeh Pueblo, 30 miles northeast of Bandelier, one concern of this unnatural erosion is that it threatens to undercut the buildings and other sites where the ancestors of modern Indigenous people lived, prayed and are buried. Such places still hold deep significance — they “help the culture function spiritually,” Cruz says.
Now, Young and other scientists are trying to stem the loss of Southwestern soils by reintroducing biocrusts to degraded ecosystems. “We’ve gotten awesome at growing biocrusts in greenhouses and in the lab,” says Sasha Reed, a research ecologist with the U.S. Geological Survey in Moab, Utah. With a moderate temperature and extra water and light, biocrusts that take decades to grow in the wild can sprout in as little as four months indoors.
But transplanting lab-grown biocrusts into the wild is another story. In 2015, Young, Reed and several other scientists inoculated soils in Bandelier with lab-grown biocrusts. When the crusts were in a naturally occurring dormant state, they ground them up and sprinkled them on an eroding mesa, hoping some of the pieces would sprout into the kind of living skin that had once likely blanketed the area. To increase their chances, the scientists inoculated the mesa before the summer monsoon, thinking the extra moisture might help the biocrust take hold.
Waiting for these fragile environments to heal themselves isn’t necessarily an option, Young explains. When Gen. George Patton drove tanks through the Mojave Desert in a World War II training exercise, he left behind tracks that researchers later compared to undisturbed soil nearby. Based on how slowly the tracks had recovered after five decades, scientists estimated it could take biocrusts almost 2,000 years to fully rebound.
Despite Warren’s views, however, a growing group of scientists — from Iceland to Australia — hope that re-establishing wild biocrusts will soon begin to reverse decades of abuse to arid lands and “break the cycle of soil erosion,” as Young wrote in a recent paper about the Bandelier experiment.
For these researchers, even unsuccessful experiments offer insight into how seasonal timing, soil type and other factors affect biocrust establishment. Reed now hypothesizes that cultivated biocrusts may not be hardy enough to survive in the wild. She’s growing biocrusts in an outdoor nursery near Moab in hopes they’ll stand a better chance than greenhouse- or lab-grown ones. She’s also subjecting different species of lichens, mosses and cyanobacteria to extreme heat and dryness to see which respond best to the conditions expected to hit deserts in our changing climate.
Cruz supports these efforts, but remains skeptical that they’ll be more than a Band-Aid over the large-scale degradation of desert ecosystems. Still, if restoration works, he says, “it would be good for not just the archaeological sites, but for the animals, the birds and the plants and everything else.”
Krista Langlois is a correspondent with High Country News. She writes from Durango, Colorado. Follow @@cestmoiLanglois
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