What Lichens Teach Us About the Air We Breathe

“What emerges in damaged landscapes, beyond the call of industrial promise and ruin?” asks Anna Tsing. One answer might just be lichen. Lichens can survive in less hospitable environments, including the Arctic or outer space, while other organisms must wait for the right conditions to be established. A composite organism, lichens are composed of one or more fungi, an alga and/or cyanobacteria. The fungal actants provide shelter to clusters of photosynthesizing cells, who reciprocate by converting sunlight into energy. This symbiosis partly explains why lichens are “pioneering” organisms with surprising longevity.

Thanks to their pioneering predisposition, lichens show us the “limits of liveability“—not just for lichens but for entire ecosystems. Certain species of lichen demonstrate a heightened sensitivity to specific chemicals in the air and can be considered a proxy or “canary in the coal mine” for environmental toxicity. Recording, or biomonitoring, these species over space and time indicate variations in air quality.

In this essay, I propose some creative and speculative practices for sensing past and present atmospheres with lichens, including an art installation that invites people to embody a “lichen’s perspective” on air pollution. These practices demonstrate how one might narrate changes in the chemical composition of atmospheres as a multispecies history. Doing so might help us to rethink unhelpful portrayals of environmental toxicity as an intangible, monolithic, and inevitable decline.

Lichens and mosses can serve as “sensors” offering alternate perspectives on anthropogenic pollution. Today, pollution is ubiquitous yet unevenly distributed, and this inequity demands that we attune to the ways in which toxic chemicals permeate, transform, and reproduce throughout more-than-human ecosystems. Airs, lichens, and sensing practices demonstrate the ways in which environmental harms not only cause loss, but also shape the potential for new forms of life to emerge—and new ways of taking care.

Airs Past and Present

My research interest in lichens as environmental witnesses took me to the Lichen Collection at the Natural History Museum in London. The collection houses 400,000 specimens of lichen from around the world. One of its main uses is to “plot the historic distribution of lichens,” explained my guide Roy Vickery, who has been involved throughout his career in archiving lichens and navigating their taxonomic classifications among rows of filing cabinets.

“The thing which was everywhere,” he continued, “when sulphur dioxide was at its ‘peak,’ so to speak, was Leconora conizaeoides.” He referred to a greyish-green, crusted lichen that I didn’t readily recognize.

In mid-twentieth century London, lichen biodiversity had diminished overall, but this species was allegedly “all over the place in urban areas,” reported Vickery. Records in the museum confirm that, following the UK Clean Air Act in 1956, the species “declined markedly around London with progressively diminishing sulphur dioxide pollution.” L. conizaeoides had relied on humans to keep emitting the same pollutants and producing sulphuric smogs.

But as transport, agriculture, and industry changed, so did air. What we often see around London and many parts of the UK today is a lichen called Xanthoria parietina, a scaly species that can appear sunshine yellow or yellow-green, depending on moisture and light levels. X. parietina is a nitrogen-loving lichen. Toxic to humans, nitrogen-containing pollutants from road traffic emissions and fertilizers create conditions in which X. parietina can thrive.

Indeed, nitrogen dioxide has become a prevailing focus for air pollution mitigation in the UK, following breaches of air quality limits. The government’s mitigation plan tasks local authorities with rolling out, extending, or fortifying “low emission zones” that penalize drivers of heavier-polluting vehicles. Similar schemes exist in other countries.

To monitor the effectiveness of these policies, networks of devices monitor atmospheric nitrogen dioxide along with other regulated pollutants such as particulate matter. Limit values for these pollutants have become central to environmental monitoring and regulation practices.

Yet, numbers alone are rather limited when it comes to painting “a picture of air pollution as our current reality.” After all, the question of how healthy or how breathable a particular pocket of air is can only be answered by considering its effects on individual bodies and societies over time. Numbers are only one indication of quality and can be at odds with how air quality is actually experienced in everyday life. In addition to quantitative measures, alternate modes of sensing, witnessing and storying atmospheric toxicity could offer an expanded capacity to understand and respond.

Creative and Participatory Sense Making

Sensing practices “mobilize environments in distinct ways.” That is, sensing primes our ability to make sense, to articulate the significance of something. The art of noticing lichen differs from the honed choreography of a trained scientist who seeks numerically precise measurements. This difference is an invitation to enter worlds unknown through local, small-scale, and open-ended forms of inquiry that allow us to speculate about an expanded sensorium for environmental toxicity, incorporating the perspectives of nonhuman others.

Arts-based and citizen science methods can offer imaginative ways of sensing and sampling air pollution, including street performances, walking practices, and immersive installations. Such projects—some of which work with data and methods derived from technoscience—all draw attention to modes of knowledge production that make air pollution palpable through embodied encounters. I foregrounded this sensibility when designing LICHEN ART LABS, a participatory workshop in Green Park supported by The Koppel Project, a London-based arts charity.

An introduction to sensing air with urban lichens, LICHEN ART LABS blended citizen science with creative inquiry. Participants engaged in a series of exercises for noticing and documenting X. parietina on avenues of London plane trees and a cluster of crab apple trees with the help of identification cards. The participant booklet for LICHEN ART LABS prompted, “Describe their habitat. What are they growing on? Where exactly? Draw a micro-map or diagram.” We produced close-up photographs of lichens through magnifying glasses, distorting the normal parameters of human perception.

LICHEN ART LABS adapted citizen science methods from Open Air Laboratories (OPAL). OPAL’s Air Survey invites people to inspect trees in their local areas and record the presence or absence of atmosphere-sensing lichens. The air quality data from the survey was less precise than technoscientific measurements for numerous reasons, including the fact that air quality is not the only factor affecting where lichens grow. Yet the methodology had value beyond the quantitative results it produced, as OPAL evaluation and data manager Laurence Evans explained in our interview.

“A lot of the time it’s about the broader benefits of engagement beyond just the project itself.” One broader benefit is the pedagogical, or teaching method, process. OPAL have “trained thousands of teachers in leading outdoor learning classes.” Such benefits are not explicit in OPAL’s Data Explorer Map. Instead, Evans measures and maps community engagement in terms of stories. These stories may be presented “alongside some facts and figures,” yet stories are “how people really gauge… a project’s success. Telling stories is how we’ve developed as human beings.”

In the same vein, LICHEN ART LABS engaged modes of sensing urban airs in ways that foregrounded participation, pedagogy, community, networks, aesthetic experimentation, and multispecies stories. The choice of the word “lab” referred to the idea of an open and expanded laboratory that participants could figuratively “step into.” The workshop toolkit offered an expanded repertoire of sensing practices. Forms of sensing air quality with nonhuman others—from particles of dust to lichens and birds—have the potential to expose and amplify the transformative effects of toxic air in its local specificities.

This kind of biomonitoring is a means of storying environmental qualities as survival rates, in terms of how liveable (or not) an environment is or has become and for whom—often due to the activities of certain human societies and infrastructures. It is therefore inextricably linked to environmentalist discourses and sentiments of loss as well as hope. We are called to expand our imaginative capacities by thinking and feeling with nonhuman others.

Practices for sensing toxicity make worlds and chemical kin. We found biomonitoring to be an interconnecting practice, involving movement through landscape, attuning to the environment, and becoming sensitized to multispecies worlds. I am reminded of Donna Haraway’s speculative fiction about hikers setting off to read “the newly deciphered lyrics of the lichen on the north face of Pike’s Peak.”

Sensing airs with lichens resonates with speculative or ancient and Indigenous knowledges, evoking the possibility for vegetal life possessing “senses and forms of communication that stretch beyond our wildest imagination.” Lobaria pulmonaria or lungwort, for example, is a leafy green or brown species of lichen that symbolizes the connection between airs, humans, pollutions, and lichens. Sensitive to air pollution and especially to acid rain, lungwort has become endangered in many parts of Europe, corresponding to human experiences of atmospheric changes.

In an experimental audio tour of Helsinki designed for the 2023 Biennial, the narrator prompts, “While walking around the city… your mental map of lichen’s distribution would indicate air quality too.” The voice continues, “Like lichens, our bodies can serve as unconscious sensors of the environment, as leaky containers of chemical information.” The art of noticing lichens is not just about producing data but rather observing how, like lichens, we are symbiotically infused with the material contents of atmospheres and the practices that transform them.

Lichens as Proxies (Taking Care)

In the art installation Lichen literacy, I invited exhibition visitors to embody a lichen’s perspective on air pollution. The installation featured video, text, sound, texture, archive, lichen, substrate, and magnifying glass—a range of media for sensing with lichens via partial perspectives. Lichen literacy foregrounded another species as an intermediary or “proxy” for accessing and generating insights on environmental conditions.

A proxy is, simply put, a stand-in for something else—initially, a person or capital that spoke or paid in the place of another. Sediment cores now speak for past climates, lichens for atmospheric nitrogen.

It is worth remembering that the word “proxy” stems from the Latin “procurare,” meaning “to take care of.” The phrase “to take care of” could be interpreted as “to protect.” It could also mean “to take responsibility for (something)” or “to deal with (something).” Perhaps, then, the etymology of proxy could remind us of our response-ability to care for the worlds we measure and transform.

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Featured Image: Xanthoria parietina in Green Park, London. Photo by author, 2021.

Lucy Sabin is an interdisciplinary researcher and artist based in Amsterdam. Her interests span art-science, air and atmospheres, breathing, environmental arts, sensing practices, chemical exposures, and feminist science studies. Lucy has collaborated with international research teams and galleries to engage communities in and beyond academia. Website. LinkedIn. Contact.