Biocrusts-Key To Ecosystem Health

Biocrusts are important in arid ecosystems. Photo George Wuerthner

Biological soil crusts, known as biocrusts, are lichens, algae, mosses, fungi, and cyanobacteria common on the soil surface.[i]They are critical to arid ecosystems, where they help to reduce soil erosion and maintain stability. They assist in water retention and act like soil mulch. They also create an underground network of filaments that binds soil together.

Biocrust on soil surface in Utah. Photo George Wuerthner 

In arid ecosystems, biocrusts act like living mulch that helps retain moisture in the soil, and they can inhibit the establishment of exotic annuals like cheatgrass. Once biocrusts are destroyed, it is easier to establish annuals such as cheatgrass. [ii]Indeed, the loss of biocrusts is perhaps one of the significant reasons cheatgrass has colonized so much of the West’s sagebrush ecosystems.[iii]

Cheatgrass, a flammable alien annual,  invades in areas where biocrusts have been destroyed. Photo George Wuerthner 

Despite their essential role in ecosystem stability, they are easily destroyed by ORVs, mountain bikes, and even hikers. However, the biggest factor in biocrust destruction and loss is livestock, whose hooves break up the crusts.[iv]

Even hikers can destroy biocrusts, but most destruction is concentrated in the narrow path, while cattle roam widely without regard to trails. Photo George Wuerthner

One of the adaptations of biocrusts to arid ecosystems is the ability to dry out and suspend respiration without serious consequences.[v]

Another vital function of biocrusts is nitrogen fixation.[vi] Nitrogen is essential to soil fertility.[vii] Soils with biocrusts exhibit higher nitrogen levels than where the biocrusts are absent.[viii]

The micro topography created by soil crusts aids water infiltration.[ix]

Cattle grazing Grand Staircase Escalante National Monument, Utah. Photo George Wuerthner 

Yet the destruction and loss of biocrust get almost no attention from federal and state agencies that manage rangelands. Until cows learn to fly, it is impossible to graze any area without destroying the crusts.


[i] Roger Rosentreter, 2021 Biological Soil of Crusts of North American Drylands: Cryptic Diversity at Risk

[ii] Root HT, Miller JED, and Rosentreter R (2020) Grazing disturbance promotes exotic annual grasses by degrading biotic soil crust communities. Ecological Applications 30: e02016.

[iii] Serpe M, Orm JM, Barkes T, and Rosentreter R (2006) Germination and seed water status of four grasses on moss-dominated biological soil crusts from arid lands. Plant Ecology

185: 163–178.


[v] Roger Rosentreter, 2021 Biological Soil of Crusts of North American Drylands: Cryptic Diversity at Risk

[vi] Belnap J (2002) Nitrogen fixation in biological soil crusts from Southeast Utah, USA. Biology and Fertility of Soils 35: 128–135.

[vii] Dregne HE (1983) Desertification of Arid Lands. New York: Harwood Academic Publishers 1–15.

[viii] Belnap J and Harper KT (1995) Influence of cryptobiotic soil crusts on elemental content of tissue of two desert seed plants. Arid Soil Research and Rehabilitation 9(2): 107–115.

[ix] Eldridge DJ and Greene RSB (1994) Microbiotic soil crusts: A review of their roles in soil and ecological processes in the rangelands of Australia. Australian Journal of Soil Research

1994(32): 389–415.





  1. Maggie Frazier Avatar
    Maggie Frazier

    This isnt exactly the same subject – but the issue is very close. Worth a read for anyone interested in the whole livestock-wild horse mess! My comment on this roundup is below:

    I choose the No Action-No Gather, Removal or Population Control Alternative.
    These herds are the ones least familiar to the public which would appear to be the REAL reason that the BLM is tossing so many possible methods of sterilization at them since, obviously there wouldn’t be as much backlash as there would be with better known herds in a less remote area. Without the thousands of people who normally would be outspoken with other herds, I assume the BLM feels they will be able to pretty much devastate these herd families without notice. Its obvious that after gelding 95% of the stallions and doubling the contraceptive moves on the mares, of course, these herds will simply get older and die out, which naturally is what the BLM wants!
    One of my many questions would be since we already have a reasonably safe, somewhat researched & reversible(?) birth control PZP which has been used in several herds and WORKS – why the current “throw EVERYTHING at the wall & see what sticks” routine? I’m guessing because in order to facilitate the actual true goal of the BLM – which is destroy ALL herds – this is worth a try.
    The idea that if it works too well, you can always bring horses from other HMAs into the North Lander Complex. Sure, which will dilute any of the wonderful genetics that already exist there.
    These herds are doing well in their particular home areas BECAUSE they have been pretty much left alone – as Wild animals that is a good thing – the best thing, really.
    The idea put forth that this is done thru “Land Use planning” and only revised every 20-30 years? Wrong..
    Then there is the true elephant in the room – livestock! The actual non-native animals – cattle & sheep – that ARE responsible for the devastation done to the land & water in every single HMA(by the way, HERD MANAGEMENT AREA)the herd in question would be Wild Horses or Wild Burros, in many instances – NOT livestock herds – Wild herds.
    If ever the BLM’s end results were in question – what they want to do here should make it clear to anyone exactly WHAT those end results would be.

    1. Ida Lupine Avatar
      Ida Lupine

      Isn’t it awful. Shocking cruelty really. But until people cut down on the beef they eat, I wonder how much can really be done. Buying up the land leases as the interesting article about the Western Watersheds Project is one way. I feel bad because the cattles are just as much victims as any other animal life affected by so many human activities.

      I don’t eat it myself and haven’t for decades.

  2. Ida Lupine Avatar
    Ida Lupine

    Thanks again for another really interesting and informative post!

George Wuerthner is an ecologist and writer who has published 38 books on various topics related to environmental and natural history. He has visited over 400 designated wilderness areas and over 200 national park units.

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George Wuerthner