Meet the biocrust: the community of plants and microbes keeping 700 million tonnes of dust on the ground

A new study has highlighted the global importance of biological soil crusts – or “biocrusts” for short.

Comprising a community of microbes, lichens and non-vascular plants, biocrusts act as the “skin” of drylands, stabilising the soil and reducing erosion.

Now, a study published in Nature Geoscience has combined experimental data and modelling to estimate the effect of biocrusts on the global dust cycle. The work was led by Emilio Rodriguez-Caballero at the University of Almeria in Spain.

The dust in the atmosphere can affect our climate in several ways. Dust particles scatter solar radiation, act as focal points around which ice and clouds can condense, and can carry nutrients and organic matter around the world. There’s also some evidence that dust can carry pathogens, such as viruses and bacteria, from one place to another.

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Most dust is generated in drylands, which cover about 12% of our planet’s land surface. The new study suggests that the presence of biocrusts in drylands greatly reduce the amount of dust that would otherwise make its way into the atmosphere.

The authors estimated that the removal of biocrusts would, on average, lead to the emission of an additional 700 teragrams (trillions of grams) of dust per year – about 60% higher than the current value.

Biocrusts are threatened by climate change and changes to land use. If the current predictions of a decrease in biocrust cover by 2070 are fulfilled, this is likely to cause a 5-15% increase in global dust emission and deposition – with downstream effects on the climate, environment and human health.

The authors called for biocrusts to be considered in future environmental modelling.

“Studies analysing dust cycling and its effect on Earth system functioning and human health need to incorporate all the interrelated effects of biocrusts, which up to now have been overlooked,” they write.

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