How to Be More Like Biocrusts in Precarious Times
This essay on desert biocrusts, care for the uncharismatic, and community building is part of the Companion Species series, which investigates a complex, interconnected, and co-constituted web of beyond-human relating. Series editors: Tessa Archambault, Dylan Couch, Kuhelika Ghosh, Ellie Kincaid, and Bri Meyer.
What surprises me is the smell. It is earthy, thick, and moldering, and it makes me instantly recoil. Fin, a researcher here at Arizona State University’s (ASU) School of Life Sciences, tells me this is how most people react. Her desk is covered in Petri dishes, arranged in a rich palette of artist’s colors, from swampy green to high-vis orange. Their textures range from cracked paint to sticky gloop that you can almost feel just by looking at them.
They may seem otherworldly, but what I’m really looking at are cyanobacteria, a crucial component of biological soil crusts. Also called biocrusts, these complex multispecies communities form a kind of living skin that spreads out over vast areas of arid land. Microbiomics labs like this one in Tempe are starting to tune in to the capacity of biocrusts to connect and stabilize climate futures. For the biocrusts, however, this is simply their way of being: making connections, sharing nutrients, and holding onto the precarious desert soil for dear life.
Biocrusts are microcosms in and of themselves. However, without a palette of Petri dishes or a friendly scientist to point them out to you, they can be almost indistinguishable from the soil they stabilize. In Arizona, some biocrusts look more like dirt than the dirt itself, accumulating in rough, congealing patches, slightly blackened, as if charred. At other times, they can have a smooth, blanket-like appearance.
What are Biocrusts?
Zoom in, and you will find yourself in a tangle of connections. This is a dynamic, literally ground-breaking community where nutrients are passed between different kinds of organisms, from photosynthesizing algae to nitrogen-fixing bacteria. Cyanobacterial biocrusts—the kind I encounter in Fin’s lab—are expert survivalists, clinging on where no one else can. Some biocrust organisms migrate through layers of soil to avoid the punishing desert sun. Others create sunscreens of dark pigment. When water is scarce, biocrust organisms dry out like tiny mummies and remain dormant until they are revived by increasingly sporadic rain.
Zoom out, and you will see this living skin spreading out over arid land, which covers nearly 45 percent of the globe. Although easily overlooked, biocrusts have a long and meaningful geologic history. They were some of the first organisms to make their way onto land and will no doubt endure into Earth’s increasingly arid future. As desert environments spread globally, the carbon and nitrogen capture and soil stabilization performed by biocrusts will become even more crucial.
Biocrusts are valuable sources of biodiversity, both in their own microbial composition and as habitats for other organisms. They are a lifeline to all kinds of creatures, from nematodes to plants who benefit from the increased soil fertility, to larger animals for whom they are a food source. Yet, biodiversity can be overlooked in desert environments that appear sparse or empty—even in places like the Sonoran, which is widely considered the world’s most biodiverse desert.
Biocrust Bundles
In the lab, the term “bundle” gets thrown around a lot. Biocrust-forming bacteria are inherently collaborative, bundling together communities of algae, fungi, and other bacteria. The cyanobacteria being studied in this lab secrete stabilizing filaments that attach to and connect individual soil particles. These sticky threads also act as a communication network that forms associations and passes nutrients to their “cyanosphere”—a microbial universe of symbiotic partners.
Microcoleus vaginatus, the most widespread biocrust cyanobacteria, trades carbon for nitrogen fixed by other bacteria. Although it takes place between microscopic partners, this relationship contributes as much as 45 percent of nitrogen-fixing globally, and biocrusts more broadly are estimated to account for around 7 percent of land-based carbon fixing per year. Fin is investigating how M. vaginatus singles out and attracts nitrogen fixers.
The sticky connectivity of biocrust-forming cyanobacteria is a mode of survival. Studies have shown that biocrust bundles emerge in response to the challenges of living in arid environments, only forming where nitrogen is limited. By drawing together communities of bacteria, fungi, algae, vegetation, and humans, biocrusts are able to hold on to precarious ground.
The figure of the bundle can also take us beyond the lab. For example, Jason Moore writes about the “messy bundle of relations” that produces the categories of “Nature and Society”—two concepts that should be recognized not as separate but as intertwined. The messy bundle of Nature and Society behaves like a biocrust community, where symbiotic partners actively shape and transform each other. Biocrust bundles, therefore, expose the ways in which other-than-human Nature and human Society are enmeshed, however imperfectly.
The Human Desert
People have been forming messy bundles with animals, plants, and landscapes in the Phoenix basin for around 12,000 years. Indigenous groups in the Northeast of Arizona, such as Hopi and Zuni Peoples, practice traditional dryland farming, and in the Sonoran itself, Ak-chin monsoon flood-plain farming is still used by the Tohono O’odham.
After the pathogen-aided, violent settling of the area in the early 1600s, a period of political conflict followed, for which Arizona remained more frontier than state. The idea of the frontier has evolved into a mindset that ignores phenomena like biocrusts. In Arizona, this perspective reduces the desert to a blank page, to be filled by human industries, ideologies, and inscriptions.
After the arrival of the railways in 1880, the “three C’s” of copper, cotton, and cattle radically transformed the landscape. Wildfires are also frequent, fueled by non-native grasses such as Lehmann Lovegrass, which were introduced to control erosion in the 1930s. And, as the three C’s attracted more settlers to the area, intense urbanization progressed.
In the 1960s, the environmentalist Edward Abbey described Phoenix as “a city where no city should be.” There is no escaping the fact that this is a desert. During my visit in October, the temperature hovered around 28 to 30ºC (82 to 86ºF), and people frequently told me how pleasantly cool it was. Understandably, many residents of the Tempe-Phoenix urban sprawl live in air-conditioned bubbles.
At the same time, these compensatory measures create a feedback loop of energy consumption. But with energy costs rising, the opportunity to evade the sensory reality of rising temperatures is becoming a privilege many cannot afford. It is no longer possible to deny that the five million people living in this urban area are part of a messy bundle that includes desert ecology.
Desert Ideologies
Varying land uses—industrial, urban, frontier—project an ideology of erasure onto the perceived “blank page” of the desert. Conservation can feed into the same logic if it is built around the idea of an empty, pristine wilderness. As with any ideology of discovery and conquest, the blank page has to be artificially maintained through the systematic erasure and violent displacement of Indigenous ways of being and forming bundles.
The 750,000 tourists a year who, like me, visit Saguaro National Park risk reproducing this ideology of erasure. People also pose a more tangible threat to biocrusts through trampling and damage from offroad recreational activities. There is an additional imperialist slant to this destruction, as 70 percent of U.S. military installations are in desert habitats. The intensified policing and militarization of the U.S.-Mexico border exposes biocrusts to Border Patrol vans and heavy machinery. Hence, like it or not, fraught border politics are also part of the biocrust bundle.
Biocrust bundles, therefore, expose the ways in which other-than-human Nature and human Society are enmeshed, however imperfectly.
Once damaged, biocrusts can take decades to recover, growing about a centimeter a year. In the meantime, without sticky threads to hold it together, the soil is vulnerable to water and wind erosion, threatening crop security and leading to severe dust storms. Valley fever—a fungal infection that causes flu-like symptoms and disproportionately affects disadvantaged communities—can break out when soil microorganisms become airborne without biocrusts to stabilize the soil.
Compounded by the threat of global temperature increases, Arizona has also been experiencing a fifty-year megadrought. Indigenous communities have been hit particularly hard, with the Zuni, for instance, declaring a state of drought emergency three times in the last fifteen years.
Biocrust Futures
Some scientists anticipate a reduction in carbon capture as biocrust cover is lost, leading to a spiral descent that would further accelerate climate change effects. Conversely, biocrust restoration could revive the ecosystem services lost when biocrusts are destroyed, with the greatest emphasis on contributions like soil stabilization, fertility boosts, and carbon capture.
To this end, scientists have painstakingly attempted to cultivate biocrusts in lab conditions and greenhouses to seed them directly into the landscape. This is easier said than done, given that the beneficial power of biocrusts comes from collectivity. Trying to recreate this community is like trying to reproduce jazz improvisation under lab conditions.
Introducing or reintroducing biocrusts to desert soils often involves making decisions about futurity. Studies have shown that as deserts become hotter and drier, some of the core engineers, like M. vaginatus, will start to be replaced within the biocrust by more heat-tolerant species of filamentous cyanobacteria.
Scientists are forced to decide whether to preserve the biodiversity that has been lost, or to anticipate further warming by introducing microbes better adapted to changing climates. When such losses seem inevitable, the discomfort around questions like this exposes the impulse—still alive and well—to preserve a pristine wilderness, a frontier of sorts. Yet this concept of wilderness is demonstrably opposed to the bundle-forming, collaborative tendencies of biocrusts, as one recent breakthrough bears out.
ASU researchers found that a healthy biocrust community had taken up residence under an array of solar panels. Solar panels have become increasingly popular, with an annual growth rate of 24 percent in the U.S. and Arizona among the most active states. The shade from the panels creates a kind of microclimate, which allows biocrusts to flourish in cooler temperatures, sheltered from harmful UV radiation. And, since biocrusts reduce the dust on the solar panels, they improve the efficiency of the renewable energy project.
Scientists are therefore investigating the possibility of treating solar farms as biocrust nurseries. Biocrusts generate their energy by enlisting photosynthesizing partners—a symbiosis which, in this case, includes larger partners than usual. Solar panels, microscopic organisms, farmers, and scientists are all enmeshed with each other in a photosynthesizing biocrust bundle.
However, the renewable energy industry is still an extractive activity. Worth $422 billion in 2020, solar power carries along with it the potential to reproduce the harmful patterns of late capitalism. Solar arrays still take resources to install, take up vast swathes of land, and can absorb and emit heat into the local environment. Biocrust bundles that collaborate with solar panels are not utopian, but messy, as most symbiosis is.
Sticking Together in Precarious Times
There is a marked contrast between this form of collaboration between humans, biocrusts, and technology, and the conservation message of the “Don’t Bust the Crust” campaign. “Don’t Bust the Crust” usually accompanies an image of anthropomorphic soil creatures cowering from a hiker’s boot. The messaging is clear: it encourages park visitors to stay on the trails and avoid trampling the living biocrusts. It’s possible to read the cute creatures and the catchy slogan as a conservation success story, advocating for the uncharismatic by giving visitors a face to relate to.
For the biocrusts, however, this is simply their way of being: making connections, sharing nutrients, and holding onto the precarious desert soil for dear life.
On the other hand, perhaps the problem is not the fact that biocrust organisms are uncharismatic, but the expectation that an organism must be charismatic to be worthy of care. In urging park visitors to avoid “busting” organisms, the campaign aims to preserve something pure, free from human influence. But this approach bears no resemblance to the tangled realities of climate change, where other-than-human Nature can no longer be separated from human Society. The biocrusts themselves influence patterns at global scales not by conserving themselves in isolation, but by enlisting partners—from soil to scientists to solar panels.
Facing a desertifying and increasingly precarious world may require new ways of approaching companionship with the uncharismatic. Perhaps the way forward is to model the biocrusts and form messy bundles with more-than-human life. This “dynamic coexistence” evokes Garry Paul Nabhan’s call to combat the imaginative emptying of the desert. For Nabhan, the desert is a place of enchantments, contradictions, and “shimmer”—a term he adapts from a Tohono O’odham concept, and the tendency of desert heat to ripple the air.
The antidote to blank page thinking and ideologies of erasure is an openness to “shimmering” multispecies bundles. Biocrust bundles are a beacon for living-together through precarity. More than simply learning not to bust the crust, bundle-forming means cultivating biocrusts under solar panels, letting go of the idea of wilderness, and saying goodbye to the frontier for good, in favour of smelly, sticky encounters with uncharismatic collectives.
Featured image: Several different biocrust samples. Photo courtesy of Fin Warsop Thomas, 2024.
Lizzie Smith is a Ph.D. researcher at the University of Warwick, in the field of environmental literature. Incorporating interdisciplinary perspectives, her thesis investigates contemporary ecopoetry about uncharismatic organisms. Her research interests include multispecies studies, decolonial ecologies, feminist ecologies, and posthumanism. Twitter. Contact.
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