Arid soils are protected from wind erosion by a “biocrust” whose role is to limit the amount of dust present in the atmosphere. However, this same biocrust faces a major threat: global warming. Over the next fifty years, the amount of dust in the atmosphere is expected to increase far from negligible and the effects of which are still difficult to assess.
Erosion of arid soils and atmospheric dust
The term “biocrust” is relative to a biotic crust of the earth which covers approximately 12% of the earth’s surface. It is a living layer representing the so-called surface part of soils and, most often, arid soils. It consists mainly of mosses, lichens and various cyanobacteria. By playing a major role in carbon and nitrogen fixation as well as in soil stabilization, the biocrust contributes greatly to arid ecosystems.
It turns out that the Earth’s biotic crust prevents the erosion of arid soils by the winds and at the same time reduces the amounts of dust reaching the atmosphere. Nevertheless, the real impact of the biocrust on the dust cycle in the atmosphere is relatively unknown. A study published in the journal Nature Geoscience and conducted by different departments of the Max Planck Institute (Germany) has shed more light on this phenomenon.
Part of the list of aerosols acting on the climate system, atmospheric dust comes mainly from wind erosion of arid soils. Able to travel over great distances thanks to atmospheric currents, these small grains are not insignificant. Indeed, they are able to modify the optical properties of the atmosphere. Indeed, the dust disperses the descending solar radiation and absorbs certain wavelengths emitted by the soil. In addition, it also influences the formation of clouds.
A phenomenon over which there is a threat
Complex and worrying, the journey of dust grains can have negative consequences for human health as well as for certain ecosystems. But to what extent does the biocrust help regulate this impact and how does global warming disrupt this regulation? Thanks to their study, the scientists provided results which show that the biocrust prevents the emission into the atmosphere of approximately 700,000 tons of dust per year. In other words, this living layer reduces the amount of dust in the atmosphere by 60%.
Unfortunately, global warming is undermining this biocrust, as is overexploitation of the soil. According to the researchers, the surface covered by this layer will have decreased by 25 to 40% by 2070. Thus, by letting wind erosion of the soil take over, the amount of dust entering the atmosphere should increase by 15%. . However, this increase could have important consequences on the climate.
For the moment, the climatic consequences of the increase in the quantities of dust in the atmosphere are difficult to assess. However, scientists believe that the phenomenon will have a strong impact on cloud formation and thus on precipitation. In addition, more dust accumulated at glaciers and other ice caps could hasten their melting. There is also no optimism regarding the different biogeochemical cycles as well as human health.