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

The finding matters because winter is not the dormant period it is often assumed to be. Beneath a blanket of snow, soils remain biologically active. Snow acts as an insulating layer, decoupling soil temperatures from frigid air temperatures and preventing the ground from freezing to depths that would kill or immobilize microbial communities. When snow lingers, microbes continue to decompose organic matter, respire carbon dioxide and transform nitrogen compounds at measurable rates throughout the cold season. In temperate and boreal forests, this winter-under-snow activity has been shown in earlier research to contribute a substantial fraction of annual carbon losses from soils. What the new study adds is evidence that in dryland systems — where snow is intermittent, thin and vulnerable — the presence or absence of a living soil surface can determine whether that insulating blanket persists at all.

The research, led by Yuqing Cao, Bowker, Zhao, Chamizo, Delgado-Baquerizo and colleagues under the title ‘Moss biocrusts sustain snowpack and soil function in cold deserts’, draws on long-term field monitoring of how moss-dominated biocrust cover influences both the duration and the depth of snow cover. The authors document that surfaces clothed in moss biocrusts hold snow longer and maintain deeper snowpack than adjacent uncrusted ground. The mechanism is partly physical. Moss biocrusts create a rough, porous microtopography at the soil surface, with elevated tufts and hollows that trap drifting snow and reduce wind-driven sublimation and redistribution. In open cold deserts, where wind is a dominant agent of snow loss, this roughness effect can make the difference between a snowpack that survives weeks of winter and one that vanishes within days.

There is also a thermal dimension. By retaining snow, biocrusted surfaces maintain a more stable and generally milder soil temperature regime through winter. The snow layer itself acts as insulation, and beneath it the dark, structurally complex biocrust surface absorbs and redistributes energy differently than pale, bare sediment. The consequence, as the study and the accompanying commentary by Lafuente emphasize, is that microbial activity in the soil below biocrusts continues at meaningful levels during months when uncrusted soils may freeze solid. Soil biogeochemistry — the sum of decomposition, respiration, nutrient mineralization and microbial transformations — is thus sustained rather than suspended.

This sustained activity has direct implications for the carbon cycle of cold deserts. Drylands collectively store large reservoirs of organic carbon in their soils, and biocrusts themselves are significant contributors to those reservoirs, fixing carbon dioxide through photosynthesis during moist periods and delivering it to the soil as organic matter. Winter is a season in which the balance between carbon input and carbon loss is delicate. When snow insulates the surface, heterotrophic microbes respire stored carbon slowly but steadily; when snow is absent and soils freeze deeply, physical and biological processes change abruptly, and freeze-thaw cycles can release pulses of carbon dioxide and nitrous oxide while damaging microbial cells and destabilizing aggregates. By keeping snow on the ground, moss biocrusts appear to buffer these dynamics, maintaining conditions under which soil functions proceed in a more continuous, less perturbed fashion.

The broader context of this work is the well-documented vulnerability of snow cover in a warming climate. Satellite records and ground observations across the Northern Hemisphere have documented declining snowpack extent, depth and duration, and projections consistently indicate further losses as winters warm. Research on snow drought has shown that human-caused warming has already reduced snowpack in many mountain regions, and studies of radiative forcing by dust and dark particles on snow have long demonstrated how small changes at the snow surface can accelerate melt. What the new study makes clear is that snow loss in cold deserts is not only a story about climate and atmosphere; it is also a story about the ground surface itself. Losing biocrusts removes a biological mechanism of snow retention precisely when climatic change is already eroding snow cover from the other direction — a compounding of stresses that could accelerate the degradation of dryland soils.

Biocrusts are, in fact, among the most threatened surface communities on the planet. Syntheses of global change effects have documented their sensitivity to warming, altered precipitation, and especially physical disturbance from livestock trampling, off-road vehicles, energy development and human foot traffic. Recovery is slow: cyanobacteria-dominated crusts may re-form in years to decades, while moss and lichen communities characteristic of cooler, more stable drylands can require centuries. Global assessments estimate that a large fraction of the world’s biocrusted area is already degraded. The new findings give that loss an additional dimension of concern. If biocrust destruction shortens snow cover duration in cold deserts, it exposes soils to deeper freezing, suppresses winter microbial activity, and potentially diminishes the very carbon and nitrogen inputs on which dryland ecosystems depend — a feedback loop in which surface degradation and soil function decline reinforce one another.

The study also reframes how scientists and land managers should think about seasonality in drylands. Much biocrust research has focused on the growing and rainfall seasons, when crusts are photosynthetically active and most visible in their influence on erosion and nutrient cycling. The winter findings shift attention to a period that has been comparatively neglected in dryland research, in part because cold deserts sit at the intersection of two disciplines: snow hydrology, which has traditionally focused on forests, mountains and tundra, and dryland ecology, which has traditionally focused on heat and aridity. By demonstrating that the two domains are physically and biologically coupled through the soil surface community, the work argues for integrating biocrust cover into models of snow dynamics, soil frost and winter carbon flux in cold deserts — regions that include substantial areas of the intermountain western United States, central Asia and high-altitude plateaus.

Writing in Nature Geoscience, Lafuente situates the study within this larger agenda, noting that biocrusts can substantially enhance snow retention and thereby sustain soil biogeochemistry, microbial activity and soil ecosystem functions in cold deserts. The commentary, which accompanies the research under the title ‘Winter carbon cycling beneath biocrusts’, underscores that the findings emerge from a long-term field program — a point worth emphasizing, because capturing interannual variability in snow depth, snow duration and soil response requires years of patient measurement in environments that are logistically demanding to monitor. It is precisely this kind of sustained observation that allows the causal chain from surface cover, to snowpack persistence, to winter soil function to be traced with confidence.

The implications reach toward both conservation and climate science. For land managers in cold deserts, protecting biocrusts from trampling and disturbance acquires a new rationale that goes beyond erosion control: intact moss biocrusts are, in effect, natural snow-management infrastructure. For Earth system modelers, the study suggests that the representation of dryland winter processes is incomplete without a term for biological surface cover and its effect on snow retention and soil thermal regimes. And for carbon accounting, the message is that the winter months in cold deserts — long treated as a blank interval between growing seasons — host active, cover-dependent biogeochemistry that could shift substantially as both climate and land use change. A crust of mosses a few millimeters thick, the study shows, quietly governs whether the soil beneath it sleeps through winter or keeps working — and with it, whether carbon in cold desert ecosystems remains stored or begins to move.

Subject of Research: Influence of moss biocrusts on snow retention and winter soil carbon cycling in cold deserts

Article Title: Winter carbon cycling beneath biocrusts

Article References: Lafuente, A. (2026). Winter carbon cycling beneath biocrusts. Nature Geoscience, 19(9), 1004-1005. https://doi.org/10.1038/s41561-026-02084-0

Image Credits: AI Generated

DOI: 10.1038/s41561-026-02084-0

Keywords: biocrusts, cold deserts, snowpack, carbon cycle, soil biogeochemistry, microbial activity, moss, drylands, soil insulation, climate change, ecosystem ecology, Nature Geoscience