Biological soil crusts occupy an enormous area. Researchers estimate that they cover a substantial fraction of the land surface in arid and semi-arid regions worldwide, making them one of the most extensive living surfaces on Earth. In many drylands, vascular plant cover is sparse, and biocrusts perform much of the ecological work that vegetation performs elsewhere. They fix atmospheric nitrogen, contribute to soil organic carbon, reduce dust emission by binding loose particles, and alter the albedo, or reflectivity, of the land surface. Because of these multiple roles, any widespread decline in biocrust integrity has consequences that ripple through soil stability, air quality, hydrology and biogeochemistry simultaneously.

The central concern addressed by the new research is that climate warming may push biocrust communities past physiological limits. Mosses and lichens that dominate mature biocrusts in cooler drylands are particularly sensitive to heat and drying. Laboratory and field studies over the past decade have shown that elevated temperatures can reduce photosynthesis, damage chlorophyll, and shift community composition toward simpler cyanobacteria-dominated crusts or, in extreme cases, toward bare ground. Earlier work by some of the same research community suggested that under high-emissions scenarios, large portions of the global biocrust-covered area could become climatically unsuitable by the end of the century. What remained uncertain was whether such degradation would measurably feed back into the climate system, and through which pathways.

The study tackles this question with an experimental design intended to move beyond correlation. Rather than simply observing that warmer sites have poorer crusts, the researchers manipulated conditions to isolate the causal chain: warming degrades crusts, and degraded crusts alter surface properties in ways that reinforce warming. By comparing intact and degraded crust states under controlled and field conditions, the team quantified how the loss of biocrust cover changes the exchange of energy, water and carbon between the land surface and the atmosphere. The results indicate that degradation is not a passive consequence of warming but an active participant in it, converting a biological response into a physical amplification mechanism.

One of the key pathways identified involves surface reflectivity. Intact biocrusts, particularly those with light-colored lichens and cyanobacterial sheaths, can raise the albedo of dryland soils relative to bare ground. When crusts degrade, the exposed soil is often darker, absorbing more solar radiation and warming the surface further. This darkening effect is conceptually similar to the sea-ice albedo feedback, in which melting ice exposes darker ocean water that absorbs more heat. In drylands, the magnitude per unit area is smaller, but the sheer extent of biocrust-covered terrain means that even modest albedo shifts could translate into meaningful regional energy-balance changes.

A second pathway runs through dust. Biocrusts act as a biological armor that suppresses the emission of mineral dust from dryland surfaces. When crusts are disturbed or killed, the soil becomes vulnerable to wind erosion, and dust loads in the atmosphere increase. Atmospheric dust interacts with radiation in complex ways, scattering and absorbing sunlight and altering cloud formation, but increased dust deposition on distant ice and snow surfaces darkens them and accelerates melt. Dust also settles on biocrusts themselves, burying living organisms and further degrading the crust, a self-reinforcing loop within the larger feedback. The study’s experimental evidence links crust loss to enhanced dust emission, closing an important part of this chain.

The third and perhaps most direct pathway involves carbon. Biocrusts take up carbon dioxide through photosynthesis and respire it back, but over their lifespan they contribute net carbon to dryland soils. Degradation reverses this balance: photosynthetic uptake declines while decomposition and respiration of accumulated organic matter can release stored carbon back to the atmosphere. In a warming world, this shift means that a land surface that once functioned as a modest carbon sink can flip toward being a carbon source. The researchers’ measurements capture this transition, showing that degraded crusts exhibit reduced carbon fixation and altered respiration dynamics consistent with a loss of the crust’s carbon sequestration function.

Taken together, these three mechanisms, albedo change, dust emission and carbon exchange, form the basis of what the authors describe as a degradation-warming amplification feedback. Warming degrades the crust; the degraded surface absorbs more heat, emits more dust and releases more carbon; and each of these changes contributes to further warming, both locally and potentially at the global scale. The experimental nature of the evidence is what distinguishes this work from earlier modeling studies. By demonstrating each link in the chain under controlled manipulation, the study provides a stronger causal foundation for including biocrust dynamics in Earth system models, which have historically represented dryland surfaces in a highly simplified manner.

The implications for climate projection are considerable. Drylands are expanding under warming, and the populations that depend on them for grazing and agriculture are among the most vulnerable on Earth. If biocrust degradation amplifies regional warming, then projections for these regions may be conservative, underestimating the pace of change. Moreover, because biocrusts recover slowly, often requiring decades to rebuild after severe disturbance, the feedback may be difficult to reverse once triggered. Land management practices that protect crusts, such as limiting livestock trampling, restricting off-road vehicle use and restoring vegetation cover, could therefore serve not only as conservation measures but as climate mitigation strategies with measurable regional benefits.

The study also underscores a broader lesson about the climate system: feedbacks can arise from the smallest and least conspicuous components of the biosphere. Biological soil crusts are millimeters thick and easily destroyed by a single footprint, yet they mediate exchanges of energy, water, dust and carbon across vast areas. As climate change intensifies, understanding and protecting these fragile surfaces may prove essential not only for the health of dryland ecosystems but for the trajectory of the climate itself. The experimental evidence presented here marks an important step toward that understanding, and it is likely to stimulate further research into how other overlooked living surfaces, from desert pavements to cryptogamic covers on rocks and trees, modulate the planet’s response to warming.

Subject of Research: Experimental evidence that biological soil crust degradation under climate warming creates an amplifying climate feedback in drylands

Article Title: Experimental evidence of a biological soil crust degradation climate warming amplification feedback

Article References: Smith, W. K., Villarreal, M. L., Lauria, C., Rutherford, W. A., Herrmann, S., Scholl, V., Howell, A., Javadian, M., Ji, F., Zhang, F., Burgess, M. A., Kokaly, R., Poulter, B., & Reed, S. C. (2026). Experimental evidence of a biological soil crust degradation climate warming amplification feedback. Communications Earth & Environment. https://doi.org/10.1038/s43247-026-03874-5

Image Credits: AI Generated

DOI: 10.1038/s43247-026-03874-5

Keywords: biological soil crusts, climate warming, drylands, albedo feedback, dust emission, carbon cycle, soil degradation, Earth system feedbacks, cyanobacteria, lichen, moss, climate modeling