Why it matters

In drylands, biological soil crusts, also called biocrusts or cryptobiotic soil, cover the surface between plants and do work that is invisible but critical. Cyanobacteria in the crust fix atmospheric nitrogen directly into the soil, making nutrients available to plants without any external input. Mosses and lichens bind soil particles together, preventing wind and water erosion. The physical structure of an intact crust increases water infiltration and reduces the runoff that strips topsoil.

When crusts are disturbed by trampling, vehicle tracks, livestock, or construction, that biological community collapses. Bare, compacted soil becomes vulnerable to erosion, nitrogen levels drop, and invasive annual grasses can establish in the gaps. Recovery is slow. Depending on the climate and the severity of disturbance, full recovery of a biocrust community can take anywhere from 50 to several hundred years.

Protecting intact crusts is therefore far more effective than trying to restore them after damage. And where damage has already occurred, reducing further disturbance is the single most important first step.

Trail sign in a dryland landscape reading Stay on Trails, Your steps matter, Protect Park Soils, with red desert soil and sparse native vegetation visible — A trail sign in dryland habitat. The message applies beyond parks: staying on established paths is the most effective way to protect soil crust communities.

How to do it

1Identify intact soil crusts: look for textured, bumpy, darkened, or lichen-covered soil surfaces in dryland areas. Healthy crusts often appear rough or lumpy, with dark patches of cyanobacteria or silvery-grey lichen rosettes. Bare, smooth, pale soil between plants is usually disturbed or degraded crust.
2Avoid disturbing crusted areas: stay on established trails, keep vehicles on durable surfaces, and redirect foot traffic away from fragile patches. This is the highest-impact step and requires no tools, no budget, and no expertise.
3Use protective barriers in high-use areas: in areas where people regularly walk near crust communities, install simple markers, signage, or natural barriers such as rocks or logs to prevent accidental trampling. The sign in the photo above is a good example of low-cost, high-visibility protection.
4Restore lightly damaged crusts: encourage recovery by reducing disturbance and, where appropriate, adding temporary shade structures to reduce desiccation stress. Inoculation with locally sourced biocrust material is possible in some restoration contexts, but must only use material collected locally. Non-local biocrust can introduce pathogens or disrupt the existing microbial community.
5Revegetate adjacent areas: native shrubs and grasses help shield crusts from wind erosion and create the sheltered microclimates that crust organisms need to recover. Establishing native vegetation around damaged crust patches accelerates natural recovery.

Ecological impact

Reduces wind and water erosion by binding soil particles into a stable surface
Increases soil carbon and nitrogen, improving fertility without external inputs
Improves water infiltration and retention, reducing runoff and supporting plant establishment
Supports native plant establishment by creating stable, nutrient-rich seedbeds
Slows or reverses desertification in drylands where biocrust loss is a primary driver of land degradation
Protects microbial biodiversity essential for soil function and long-term ecosystem resilience

Watch out for

Cryptobiotic crusts are extremely fragile: even a single footprint can cause long-term damage in some crust types
Do not inoculate with non-local biocrusts: this can introduce pathogens or disrupt local microbial communities
Avoid restoration work during extreme heat: crust organisms are most vulnerable when desiccated
Monitor for invasive annual grasses: they can outcompete recovering crusts and increase fire risk

The bigger picture

Biocrusts cover an estimated 12 percent of Earth's land surface and are the dominant ground cover in many of the world's drylands. They are also among the most threatened soil communities on the planet, declining sharply under livestock pressure, off-road vehicle use, and climate change. Protecting them where they still exist is one of the most cost-effective conservation actions available in arid and semi-arid landscapes.

Sources: Belnap & Lange (2003), Biological Soil Crusts, Springer; Pointing & Belnap (2012), Nature Reviews Microbiology; Rodriguez-Caballero et al. (2018), Nature Geoscience.