Gathering Moss: A Natural and Cultural History of Mosses

Kimmerer recalls a violent storm in the Adirondacks that took place in July of 1996, the most severe storm ever recorded east of the Mississippi. She and her young daughters huddled in their cabin as huge tracts of woodlands were uprooted around them. Kimmerer notes that events like this—where the landscape is almost completely denuded—are rare, but that they present an opportunity for new species, like aspen, to establish themselves. When individual trees fall due to more typical wind events, the small gaps left in the canopy of the forest are not enough for species like aspen, but these smaller spaces are good habitats for species like yellow birch. The diversity of a forest system is key to its recovery after a disturbance, because different species can utilize different size gaps and different soil conditions. The pattern by which each different species fits into a different gap in the forest is referred to as “gap dynamics.”

Gap dynamics plays out at a micro scale among moss colonies as well. When dominant species like the large carpet mosses are disrupted and clearings appear within their colonies, species like Tetraphis and Dicranum flagellare colonize these gaps. Often, both species will colonize gaps in a common environment. Since, according to ecological theory, similar species with similar needs cannot coexist indefinitely because one will eventually outcompete the other, Kimmerer wondered why she often saw both Tetraphis and Dicranum living together. She wondered if there is some hidden divergence in the two species that allows them to effectively share space.

She discovered that although both species colonize the gaps in larger colonies, they have different space requirements: Tetraphis enters larger gaps than does Dicranum. The larger gaps that Tetraphis prefers tend to occur on the sides of logs, where wood fungi have loosened the structure of the log and large pieces succumb to gravity, opening up fresh habitat on newly exposed wood. By contrast, Dicranum tends to enter gaps on the tops of logs. Kimmerer found that, although Dicranum, like Tetraphis, has the ability to reproduce both sexually and asexually, Dicranum’s cloning structures hold on tightly to its “brood branches” and cannot distribute them via the splashing of rain. Instead, these tiny branches hitchhike on passing chipmunks. Since chipmunks tend to run along the tops of fallen logs rather than on the forest floor, this is where the brood branches get scattered. The Dicranum branches then set up new colonies in the small bare spots left by chipmunks’ activity.

Many species of moss thrive in an urban environment, particularly those adapted to living on rocky outcrops. These live on buildings, statues, and other “rocky” features of the urban environment. Urban mosses tend not to be “the soft, feathery mats” seen in forest mosses (92). Rather, they stay short and cluster densely to conserve moisture. Among the most common urban mosses is Bryum argenteum, or Silvery Bryum. This is the moss most often seen in sidewalk cracks. It is commonly spread by people, who unknowingly break off shoots of the plant as they step on it, transferring these to new areas as they walk. Bryum argenteum’s natural habitat—seabird rookeries and the margins of animal burrows—is similar to city sidewalks, and the population of Bryum argenteum has grown along with the rise of cities.

Lawn mosses such as Brachythecium and Eurhynchium are also common in human-created environments. Kimmerer is distressed when people believe that these mosses are a threat to their grass lawns and try to kill the mosses. Mosses, she points out, are not able to outcompete grasses. They simply take over bare patches where conditions are not hospitable for grasses. The solution is to improve conditions for the grasses, not to kill the mosses. In areas like Portland and Seattle, where environmental moisture is high, chemicals to kill mosses are commonly sold. These chemicals leach into the water supply, poisoning other creatures—and, inevitably, mosses always return to hospitable surfaces anyway. Kimmerer points out that there is no scientific evidence that mosses are a threat to structures like roofs, where people often seek to eliminate them. In fact, a moss-covered roof is actually beneficial, because the mosses protect the shingles from sun, slow water run-off, and insulate the roof.

Kimmerer describes visiting the Manhattan loft home of Jackie Brookner. Brookner is an environmental artist. She has sculpted a boulder from wire, fiberglass, sand, gravel, and cement. The boulder sits in a pool of water and is covered with mosses Brookner placed there by inoculating the boulder with spores from the air coming in her windows and by gathering mosses on her walks in the city. The mosses on the rock, which Brookner has named Prima Lingua, actively purify the water flowing over the rock; researchers are interested in her work as a guide for purification of wastewater and urban streams. Kimmerer examples the moss and its colonies of tiny insects, thinking that artists have a valuable way of looking at the natural world and can offer insights as important as those of scientists.

The essay closes with commentary on mosses’ susceptibility to pollution. Where there is heavy pollution—particularly in the air—mosses decline. Their presence or absence says much about the health of the air in a city, and changes from one area of a city to the next or changes in speciation over time can help scientists track changes in air quality.

Kimmerer opens with a description of a smudge ceremony conducted by her uncle Big Bear. The smoke from the burning sage is used to purify and carry prayers. Kimmerer admires her uncle’s determination to open a school for local young people, where they can learn traditional outdoor skills and enter a more respectful relationship with the land. She explains that the Indigenous perspective is that each living being has individual gifts and that a fundamental part of education is discovering one’s gifts and learning to use them responsibly. Part of being responsible is giving back to the community of living beings—maple trees give their sweet sap as food for other creatures, for example, as part of a “web of reciprocity” that benefits all (100). Kimmerer notes that she constantly sees this network of reciprocity at play in her scientific study of the natural environment.

Indigenous knowledge about each being’s gifts is passed down through the generations and is the result of careful observation and intimacy with the landscape. Modern people are often cut off from the landscape and have very little knowledge about or respect for nonhuman beings. Kimmerer is grateful for the traditional knowledge given to her by Jeannie Shenandoah, an Onondaga herbalist. From Shenandoah, Kimmerer learned how humans are interwoven into the web of reciprocity that exists in nature. This inspired Kimmerer to consider what mosses’ gifts might be and what their reciprocal role with humans is. Shenandoah could only tell her that mosses were not traditionally used as food or medicine.

From her academic research, Kimmerer was already aware that mosses have been used in many societies for their insulating properties and as decoration. She was sure that mosses must have more unique gifts to offer humans, however. Because Shenandoah had taught her that plants occur where they are needed, Kimmerer decided to study how the locations of mosses might give clues to their uses for humans. Their locations made her think about their affinity for water and their sponge-like properties. When she read that mosses were often used as diapers and as sanitary products during menstruation, she reflected that the domination of science by men for so many generations had led to this important use for mosses being obscured in the scientific record. She turned to the work of a female ethnographer, Erna Gunther. From Gunther’s work she learned that mosses were also used as sponges in cleaning fish and in fire pits for steaming food. Moved by these contributions by the humble mosses, Kimmerer asks what humans can offer in return. She suggests that environmental stewardship is the answer.

Kimmerer describes dancing barefoot atop the surface of a Sphagnum bog, comparing it to the sacred Water Drum of her Anishnaabe people because both, to her, represent the meeting place of the seen and the unseen—the physical and the spiritual. She is barefoot because she has learned that the bog will sometimes suck down her shoes—a sneaker she lost years ago still sits somewhere in the depths of the bog. Sphagnum bogs, also known as peat moss bogs, are an ideal habitat for mosses. Here, the mosses are constantly wet and not overshadowed by other plants. The Sphagnum forms a spongy mat on top of the still water. As it decays, it fills the water with tannic and humic acids, making the water inhospitable for other plants.

Kimmerer finds it amazing that most of each Sphagnum strand consists of dead matter fringed by thin bands of living cells. The hollow, dead cells function as an important part of the plant, holding water and saturating the soil. This prevents oxygen from getting into the soil and is another reason this environment is hostile to other plants. It even slows the root growth of the surrounding trees, keeping the canopy open to get sunlight to the bog. In this anaerobic environment, decay progresses over centuries rather than days or weeks. This is why human bodies buried in peat bogs can be preserved for thousands of years. Slow decay means that the minerals in dead matter cannot be broken down, and the environment lacks nutrients for higher plants. As a result, some bog plants have developed the adaptation of eating bugs.

In a bog, only the top layer of moss is living. Underneath is a thick mat of dead, preserved Sphagnum moss. The living layer continually grows upward, wicking up water from the dead layers beneath. The dead, compressed layer is what humans cut and use as peat. Peat has been used as bandaging for wounds, as a fuel source, as a flavoring element in scotch whiskey, and as a soil amendment for gardens. Each part of the bog is suited to different species of Sphagnum, and each part of the bog feels different to Kimmerer’s bare feet. She notes that it is possible to reach down into the peat and feel how much cooler it is than the surface air. This is why people traditionally used peat bogs as a kind of natural refrigerator. The layering effect of mosses in a bog means that scientists can cut samples out and gather data on how the surrounding landscape has changed over time.

To Kimmerer, the bog is “the living embodiment of the Water Drum” (118). She dances on its surface, setting the top layer into motion like a responding dance. She compares the deep layer of peat to memory, holding her up and connecting her to the past. She imagines that she can hear her ancestors singing about both good times and dark times in their history. She observes that “Memory, like peat, connects the long dead and the living” and asserts that “Spirit, like water, [is] wicked up from below” (119). She is proud that, despite the attempt made to exterminate her ancestors, she is still here, like the living layer of Sphagnum rising up from the dead, below.