Inside Climate News reports:

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.

Some strains of lichen, which are communities of fungi and algae in symbiotic relationships, survived the planet’s last three mass extinction events, but a study published last week in the Proceedings of the National Academies of Sciences shows global warming is likely causing a decline of lichens that are key components of biological soil crusts. If the organisms die and crusts crumble, deserts will expand and soils in arid regions will dry up and potentially blow away as dust in the wind. [Continue reading…]