Does the Future of our Planet Depend on Moss?

Art & Science

Southwest of the Boundary Waters, in a young black spruce forest in the Chippewa National Forest, stand ten octagonal chambers built over a bog. Metal walkways that seem to float over the spongy land connect these structures, creating a startling contrast of futuristic chambers in an otherwise pristine, natural wetland.

It could be the setting for a science fiction movie, a scene from another world. Indeed, in these atmosphere and temperature controlled chambers, researchers are trying to get a better grasp on how rising temperatures and carbon dioxide levels will shape the world to come.

An enclosed, transparent space with trees growing inside it.
Randy Kolka, SPRUCE project leader and research scientistOne of the climate-controlled enclosures at the Spruce and Peatland Responses Under Climatic and Environmental Change Experiment (SPRUCE).

This is the Spruce and Peatland Responses Under Climatic and Environmental Change Experiment, or more simply, SPRUCE. For the better part of a decade, SPRUCE has been the largest climate change experiment in the world. The ten chambers here are equipped with state-of-the-art sensors and technology that create different temperatures and climatic conditions that simulate hypothetical warming conditions brought on by climate change. Temperatures in the enclosures are either ambient, to match current conditions, or elevated to +2.25, +4.5, +6.27 and +9 degrees Celsius, or about +4, +8, +12, and +16 degrees Fahrenheit.

Half the enclosures have an elevated CO2 levels of 900ppm, while the other half retain the current ambient CO2 levels (about 400 ppm). Since it became fully operational in 2016, SPRUCE has attracted scientists from around the world. At any given time, there are between thirty to forty groups working on various research projects. In the space-age, octagon enclosures, teams can investigate CO2 absorption and methane release, model how carbon cycles will change, and conduct numerous other studies into how a changing climate will impact one of the most important ecosystems in our warming future: peatlands.

At the center of this research is moss. In particular, the sphagnum moss that grows throughout the peatlands of the boreal forest, the great expanse of forest that encircles the earth’s northern latitudes and reaches down to northern Minnesota.

You’ve probably stepped on a shaggy patch of sphagnum moss or seen it along the edge of a wetland. Maybe you paid attention to it, maybe not.

Though it doesn’t inspire the grandeur as a centuries-old white pine or have the same cultural heft as a birch tree, sphagnum moss, and the peatlands where it grows, plays an outsized role in regulating atmospheric carbon.

In the Boundary Waters and throughout northern Minnesota, sphagnum moss has been at work sequestering carbon since the glaciers retreated. Because the moss is highly resistant to microbial decay, some of the carbon absorbed by the moss does not get released as CO2 through the process of decomposition.

Instead, the moss, with its stores of carbon, gradually accumulate into the wet peat that — because plant activity is greater than the rate of decomposition — accumulates into peatlands. After several thousand years, these accumulated layers of peat have become one of the largest stores of carbon on the planet.

In fact, peatlands are so effective at capturing carbon, that while they only comprise about three percent of the earth’s land surface, they store around 30 percent of its terrestrial carbon.

But the atmospheric balance of carbon that peatlands has done so much to create is in danger. Warming temperatures may drastically change the ecosystem in which sphagnum moss thrives and flip peatlands from being a crucial means of sequestering carbon, to becoming a major source of carbon emissions. Such a feedback loop would create a snowball effect, where rising temperatures and carbon emissions trigger even greater carbon releases, increasing the rate of temperature change.

A mustachioed gentleman in shaded glasses and a U.S. Forest Service ballcap.
Randy Kolka, SPRUCE project leader and research scientist

Randy Kolka, a research soil scientist, and the USDA Forest Service Principal Investigator of SPRUCE, who has been with the project since its conception in 2009, says that this is one of the main reasons that the largest climate change experiment in the world is in northern Minnesota. “Peatlands are critical to our future climate as they have been sinks for carbon for thousands of years.

Now, the balance is shifting from being carbon sinks, to lesser sinks, and in some cases carbon sources, exacerbating climate change.”

Understanding this shifting balance of how northern peatlands — many of which are found throughout the Boundary Waters — respond to climate change is crucial to forecasting our warming future.

• • •

SPRUCE is part of the Marcell Experimental Forest, which was established in the 1960s to specifically study the impacts of land management practices on the water quality of a water-rich forest.

At the time of its founding, little was known about peatlands, “They were once thought to be wet, mosquito infested areas that should be drained to be more productive, mainly for agriculture,” says Kolka. To some degree these ecosystems are still somewhat misunderstood and understudied. The work researchers conducted at SPRUCE has had global significance. “SPRUCE is changing the way we think about peatlands and how important they will be in our future climate. Even in just seven years, there have been over 100 publications and over 2,000 people have visited the site,” says Kolka.

This collective work has helped evolve our understanding of the importance of peatlands, both as a place that holds vast quantities of carbon, as well as other greenhouse gases. These advances have spurred research in other regions of the boreal biome — Siberia, Canada, Scandinavia — and have allowed scientists to better understand the issue of peatlands and climate change on a global scale. And while we now know their importance as a major carbon sink, we also now know that peatlands can flip to become a major source of carbon emissions.

Sphagnum moss with flexible pipes running next to it.
Sphagnum moss near experimental equipment inside an enclosure.

Essentially, this happens when the microbes become more active so that the rate of decay increases to be greater than that of plant activity. Kolka points out that since monitoring at Marcell began, there has been at least two times that researchers have observed this flip.

The first time was in the fall of 2011, when warmer conditions extended into the fall, prolonging the growing season so that while the plants entered a state of dormancy, the warmer temperatures created condition that allowed microbes to remain active and continue to decompose plant matter, emitting CO2. Because the moss and other plan life had gone dormant, they were not absorbing the amount of CO2 they normally would. With increased rates of decomposition, the balance shifted and the peatlands began to emit carbon.

The other time was in 2021, when drought conditions caused fires to erupt throughout the northland. The drought also caused water levels in peatlands to drop. This caused soil comprised of partially decomposed plant matter, soil that had been wet and underwater, to be exposed to the air and dry out.

Again, it goes back to the microbes.

In this case, because microbes in the air are more efficient than microbes underwater, the rate of decomposition increased, thus flipping the peatlands, causing them to release more CO2 than they absorbed.

Though peatlands can flip, the change is not necessarily permanent. Whether or not they are a carbon sink or carbon emitter depends on conditions, and conditions change.

“Given the predicted warming trends, at some point they will all flip. That will vary by latitude, associated changes in precipitation, and other factors. But if we warm a few more degrees globally, you will really see the carbon balance in peatlands shift from sink to source,” says Kolka.

Unfortunately, conditions are on pace to rise in a way that will lead to this. One of the major findings at SPRUCE is that a moderate increase temperature, of +2.5 degrees Celsius, will flip the ecosystem into a source of carbon emissions. To no surprise, enclosures with higher temperatures, emit more carbon.

A sign reading "Welcome to a warmer future +9.0 degrees C, Ambient CO2 Plot 17"
Sign above the entrance to an enclosure.

In chambers with the highest temperature differentiation of +9 degrees Celsius, carbon emissions have led to the loss of approximately 2.5 inches of peat. The ground elevation dropped by 2.5 inches. What had taken centuries to accumulate, vanished in 5-6 years.

Increased temperatures appear to be bad news for trees, particularly black spruce and tamarack. One reason is that warming temperatures bring an increase of false springs, where the temperature rises to say 45 degrees Fahrenheit in February only to drop back down to -10. Trees think it is spring but are subsequently frost bitten, needing to start their annual cycle over again. This temperature swing forces the trees to draw on carbohydrates and energy stores which, the more it happens, weakens the trees and makes them more susceptible to disease, stunted growth and premature death. The winners are the shrubs, such as blueberries, which thrive and grow at a faster rate in warmer conditions. In the warmer chambers, shrubs have experienced a longer growing season of up to ten weeks. As the canopy and leaf cover from the shrubs spread, they shade out the sphagnum moss, choking out the light it needs and stunting the moss growth, negatively impacting the plant community most responsible for sequestering carbon.

• • •

Globally, this summer was the hottest on record. Newsfeeds were filled with stories of consecutive 120-degree days the southwest, a heatwave ominously named after figures in a mythological hell — Cerberus, then Charon — scorched western Europe. Changing climatic patterns are being felt in northeastern Minnesota and the Boundary Waters as well. Southern tree species such as oak and maple are moving into the boreal forest.

Since its founding in the 1960s, the Marcell Experimental Forest now has a three week longer growing season and temperatures have increased by about 2.2 degrees Fahrenheit – consistent with the rest of northern Minnesota.

The changes that will come to northern Minnesota will go far beyond a change of species and trees. Northern Minnesota, home to an extensive amount of peatland and wetlands, which hold an incredible amount of carbon, will play a crucial role in this warming future. One small 25-acre area of peatland in the experimental forest holds 11,000 metric tons of carbon, equivalent of 120,000 flights between Bemidji and Minneapolis.

From a scientific stance, and an emotional, human perspective, this future can be hard to wrap one’s head around. Research projects like SPRUCE help us better understand what might happen in the small corner of the boreal forest so many of us love. They also highlight the global significance of the Boundary Waters in this new era of climate change, and renew the urgency to curb carbon emissions and preserve the ecosystem that we all depend upon.

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