Decline of Tiny Dryland Lichens
Lichens that help hold together soil crusts in arid lands around the world are dying off as the climate warms, new research shows. That would lead deserts to expand and also would affect areas far from the drylands, as crumbling crusts fill winds with dust that can speed snowmelt and increase the incidence of respiratory diseases.
Biologically rich soil crusts, sometimes called cryptobiotic soils or biocrusts, are spread out across dry and semi-dry regions of every continent, including Antarctica. In total, the crusts cover more than 6 million square miles—an area about the size of Russia.
They are assemblages of hundreds of organisms, mostly algae, fungi, lichens, mosses and even cyanobacteria. Woven together by eons of evolution, the organisms become keepers of soil, building intricate organic structures with bacterial filaments and sticky polysaccharides to hold grains of earth and sand in place. Soil crusts build up land, slow erosion and suck a lot of carbon dioxide out of the atmosphere, storing it in the soil. Some crusts even fix nitrogen that fertilizes plants.
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