"Welcome to a warmer future," reads the sign above the door to the strange translucent cylinder towering in the middle of a Minnesota peat bog.
Inside the 26-foot-high, open-roof chamber, dozens of high-tech instruments with names like dendrometer, phenology camera, and mini-rhizotron are collecting information on the plants, soil, water, and air within the 1,000-square-foot patch of damp bog. A warm breeze streams steadily from an air duct, and underground heaters radiate warmth into the soggy earth, keeping the chamber a toasty 16 degrees warmer than the surrounding forest peatland.
"Things have bloomed in here four to six weeks earlier. The blueberries were ripe three weeks before" berries outside the chamber, says Stephen Sebestyen, a hydrologist for the U.S. Forest Service who's giving visitors a tour. "I mean, look at this," he says, gesturing toward a small bog rosemary plant with swelling buds, ready to flower. "They're not doing that within the ambients"—by which he means unheated chambers—"or outside."
There are 10 chambers like this one nestled within the Marcell Experimental Forest, a 2,800-acre piece of the Chippewa National Forest north of Grand Rapids. They are part of a "whole ecosystem warming experiment" called SPRUCE—Spruce and Peatland Responses Under Changing Environments.
The goal of the SPRUCE project is to help understand how climate change will affect Minnesota's vast stretches of northern forest peatlands—expansive wetlands that are home to millions of spruce and tamarack trees, dense carpets of moss, and a huge variety of birds and other wildlife.
Warmer and Wetter
The Marcell Experimental Forest was set aside by the federal government in the 1960s to perform long-term research on these peatlands and their surrounding watersheds. The SPRUCE project began more recently as a collaboration between the Forest Service and Oak Ridge National Laboratory, with funding from the U.S. Department of Energy. The chambers were completed in 2014 and the experiment became fully operational in summer of 2016.
"We never set out to be a climate research center," says Sebestyen. But over the past several decades, the peatlands in the forest have seen many climatic changes, from longer growing seasons to earlier snowmelt.
"We're seeing two signature changes: It's warming, and it's getting wetter," says Kenny Blumenfeld, senior climatologist for the Minnesota State Climatology Office. Minnesota's average temperature has risen 2.5 to 3 degrees since 1970, and scientists project continued warming over the coming decades. The sharpest temperature climbs have occurred during Minnesota's infamously cold winters. "We're seeing that winter temperatures are warming much faster than summer temperatures," says Blumenfeld, "about 10 times faster than summer since 1970." That's among the fastest rising winter temperatures in the lower 48 United States.
While some residents may not mourn the loss of bitterly cold winters, Minnesota's ecosystems depend on deep cold spells to control pests and keep out heat-loving invasive species. Furthermore, two important industries in the state—recreation and timber—depend on predictable periods of snow cover and frozen ground. Minnesotans aren't yet seeing hotter summers, but we might by mid-century or sooner, according to climate models.
Increased precipitation is arriving in the form of more intense downpours, but not necessarily more frequent rainy days. This increases the risks of flooding and erosion problems. And while drought is not yet increasing in Minnesota, warming temperatures and longer stretches between heavy rains may eventually create water stress in some areas. "Generally we think that we're going to be seeing more rain, but on fewer days," Blumenfeld says. "And that would lead to more dry periods."
As Minnesota's climate changes, our forest peatlands are expected to change as well. The SPRUCE project may give scientists a sneak preview of their fate.
Forest peatlands are something of a hidden gem in Minnesota. "Peatlands are pretty rare on the landscape. And Minnesota is unique—we've got 3 million acres of forest peatlands," says Marcella Windmuller-Campione, assistant professor of silviculture at the University of Minnesota.
Peatlands tend to be overlooked by the public, as they aren't the most inviting places. The perpetually soggy, acidic soils create conditions where few species can thrive—but those that do are special. "They're this lesser-touched beauty. There are so many unique moss species and other rare plants," says Windmuller-Campione, citing rare orchids such as the endangered bog adder's mouth and threatened ram's head lady's-slipper.
The peatlands are home to an abundance of bird species, drawing avian enthusiasts from around the world. "They also provide a large amount of timber products," she notes, explaining that the slow-growing black spruce trees produce long wood fibers that can be used to make high-quality paper. In addition, forest peatlands can help filter water before it heads downstream.
Peatlands provide yet another important service: They are Minnesota's biggest carbon hoarders. While peatlands make up only 3 percent of the earth's landscape, they hold 30 percent of the supply of soil carbon. This is because the waterlogged conditions in peatlands make it hard for plants to decompose. So new plants grow faster than dead plants can rot, and carbon-rich mats of vegetation and other organic matter, called peat, build up over time. More carbon is locked away than is released from peatlands, making them carbon "sinks." Layer upon layer of peat has built up in the Experimental Forest's bogs over the 12,000 years since Minnesota's last glaciers melted. This saturated blanket of old plants can be up to 30 feet thick in some places.
But with temperatures on the rise, these massive carbon vaults may not be quite as reliable as they once were. Warmer temperatures may cause the peat to decompose more quickly, releasing more carbon dioxide, a "greenhouse gas" that warms the planet by trapping the sun's heat. Human activities, such as burning coal and oil for energy and converting natural lands to agricultural use, have released large amounts of extra carbon dioxide into the atmosphere—exaggerating the heat-trapping effect of Earth's natural greenhouse. Decomposing peat also releases methane, another greenhouse gas, which is 30 times more potent than carbon dioxide when it comes to heating the planet.
Scientists are concerned that these changes may lead to a shift in the balance, making these peat bogs sources of greenhouse gases rather than storehouses of carbon. This would only speed up global warming.
SPRUCE scientists aren't just monitoring climate change. They're creating it for the bits of peatland inside the heated chambers.
The SPRUCE project is actually "two experiments in one," according to Stephen Sebestyen. First, heat is added to most of the chambers at a range of different temperatures to see how the peatlands react to warmer conditions. Two of the chambers have no added heat for comparison. Half the chambers also have extra carbon dioxide pumped in through the air ducts to mimic potential continued increases in the greenhouse gas from human activities. In addition to warming the planet, the extra carbon in the air may cause plants to grow faster, depending on other conditions. So SPRUCE scientists are testing a future scenario where both temperatures and carbon dioxide levels are higher.
"Alkalinity, pH, specific conductivity, total nitrogen, total phosphorous, nitrate, sulfate …" Sebestyen ticks off the many things SPRUCE scientists measure in a single bucketful of water that sputters from a pipe draining from the bog. The same thing happens with soil samples, which are distributed to dozens of scientists who examine everything from the genetics of the bacteria to the chemistry of the peat. The instruments inside the chambers are constantly measuring gases, taking thousands of photographs, monitoring tree growth, and more. Says Sebestyen: "What do we get? We get a lot of great science. It's a world-class research facility."
Much of the data collected from SPRUCE is sent to Oak Ridge National Laboratory in Tennessee. There, a team of scientists pores over it, hoping to stitch together the story of what is happening inside the chambers. But the SPRUCE project also draws many scientists from around the world to its doorstep in Minnesota. That's because the experiment is one of a kind. Discoveries made during the SPRUCE project may help us begin to understand what will become of northern forest peatlands across the globe as the planet heats up.
The project has been well received by locals, says Randy Kolka, the Forest Service's lead scientist for SPRUCE. Neighbors come by all the time to explore and ask questions.
"It's been a really good teaching resource for the community," says Kolka. Project staff members frequently lead tours of the experiment, most of them for community organizations and schools. Kolka says it is often the younger kids who have the most pointed questions about the experiment, such as "Is this poor tree gonna die?"
"And it really brings you back down to earth on why you're doing it," he explains, "because those are the kind of questions that really are going to inform the larger-scale questions of who's going to win and who's going to lose in this new environment."
The project has also brought some economic benefits to town. The chambers were built by a local contractor, and the project buys electricity and propane from local suppliers to heat the chambers. Visiting scientists also patronize Grand Rapids' hotels and restaurants.
All in all, north woods residents seem to be taking ownership of the experiment that has cropped up in their neck of the woods. "Minnesota should be very proud to have this experiment. It's going to inform our future generations about how climate is going to affect the planet," says Kolka. "And it's all in our back yard in northern Minnesota."
The Canary in the Coal Mine?
Back inside the hottest chamber, the plants are looking—well, a little bit sad. The spruce trees have lost some of their needles. A few tamarack tree branches are lined with tiny brown needles, possibly ones that emerged too early in spring, only to be killed by a sudden cold snap. "The Labrador tea and leatherleaf are really confused," jokes Sebestyen.
Minnesota's spruce peatlands are on the very southern border of their range, which extends much further north into the Arctic. So these peatlands are already living on the edge of tolerable conditions. As the climate changes, warmer temperatures may force the spruce and other cold-hardy species to shift north and be replaced by more southerly species.
These unique conditions are part of what drew SPRUCE scientists to northern Minnesota. Will Minnesota be the canary in the coal mine, alerting us to big changes coming for northern forest peatlands around the world? The SPRUCE experiment brings us a step closer to finding out.