Peatland forests: the swamps and bogs where tree-planting isn’t clear-cut

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This story is part of the Landscape News series Forgotten Forests.

The Scottish peatlands have become an unlikely provocateur of one of environmentalism’s main questions of late: is tree-planting always a good thing?

Scotland’s Flow Country, a 400,000-hectare expanse of peatlands, mountains and straths (wide river valleys) that straddles the country’s northernmost two counties Caithness and Sutherland, is now a prized landscape and proposed World Heritage site, both for its beauty and the benefits it provides (more on those later). 

Ground-nesting birds such as curlews (Numenius arquata), greenshanks (Tringa nebularia) and dunlins (Calidris alpine), and mammals like red deer (Cervus elaphus) and otters (Lutra lutra), live in its soft lands and dark waters, colored by the decaying debris known as peat. The lumpy, waterlogged ground is peppered with sedges and lined with vivid-green sphagnum moss. 

“It’s one of Britain’s last true wildernesses, and the largest area of bog in the region as well,” says Tom Sloan, a scientist at the University of York. 

Peatlands are a kind of wetland ecosystem whose soil is made almost entirely from dead and decaying plant material, which decomposes slowly under year-round waterlogged conditions. They occur in almost every country on Earth, and cover around 3% of global land surface. As well as being home to significant and unique biodiversity, they also punch above their weight in carbon sequestration, stashing twice as much carbon as all the world’s forests.

But these swampy, hard-to-access ecosystems frequently suffer from an image problem: and the Flow Country’s bogs are no exception. “If you look back at descriptions from the 18th and 19th centuries, it’s always described as quite bleak,” says Sloan. “There is this tendency to look at these environments as being kind of barren and unproductive.” In a letter to famous Scottish novelist Walter Scott in the early 1800s, geologist John MacCulloch described the peatlands as “hideous, interminable…  a desert of blackness and solitude and death… If there was a blade of grass anywhere it was concealed by the dark stems of the black, black muddy sedges, and by the yellow melancholy rush of the bogs.” 

In that context, when the British government offered nationwide tax incentives in the 1970s and 80s for tree-planting to boost timber production and increase woodland coverage, the Flow Country’s cheap and ostensibly-unproductive peatlands were a popular candidate. Around 17 percent of the region was planted with exotic conifers, mostly lodgepole pine (Pinus contorta) and Sitka spruce (Picea sitchensis). 

It wasn’t an ideal location for that kind of forestry. “The trees that are planted there are not great wood quality,” says Sloan; “they’re not going to produce much of a commercial yield in a lot of circumstances, because of the wet conditions in which they have to grow.” But the policy did not specify any land-quality restrictions, and most investors in the Flow Country were wealthy individuals looking to minimize tax bills, rather than to create profitable, sustainable forestry projects. 

Now, scientists and community leaders say the policy tells a cautionary tale. “In a lot of ways, it was a very good aim,” says Sloan, “but it had unintended consequences in the way it was applied.” 

Initially, environmentalists’ concerns about the process were biodiversity-based. To give the plantations a better chance of survival in the waterlogged bogs, the peat was drained and ploughed to create drier ridges and keep tree roots out of the water. This destroyed the habitats of many keystone species, particularly the bogs’ characteristic ground-nesting birds, which were further persecuted by predators such as red foxes [Vulpes vulpes], hooded crows [Corvus cornix] and pine martens [Martes martes] as forest cover increased. 

Now, scientists like Sloan are exploring the carbon-storage implications of those plantings. He and his colleagues have observed that where the water table has been lowered for forestry, peat begins to compact, compress and oxidize, releasing carbon into the air through the process. “Now, the question is whether you compensate for this through the carbon that’s getting locked up in the biomass of the wood,” says Sloan. “But our studies have found that’s probably not the case – you’re still getting a net loss.” What’s more, the largely low-quality wood yielded in the Flows is mostly destined for fuel. “So even the carbon that is stored in the trees will probably return to the atmosphere quite quickly,” he says.  

In some places, such as the fenlands (low-lying wetlands) of Finland, where high-volume, high-quality wood can be produced with limited disruption and then ‘locked up’ in furniture and construction for hundreds of years, this kind of forestry can be net-positive from a carbon perspective. “Broadly speaking, in a lot of places, planting trees is a terrifically good thing,” Sloan says. “But in this specific environment [of the Flows], it turns out that’s a lot more questionable. It was an unintended consequence of a policy that had a lot of good intentions, but could have been thought through better.”

This all serves as a case study for the broader question of tree-planting’s efficacy, which has increasingly been a subject of conversation as tree-planting rises on agendas as one of the most important actions we can take to mitigate climate change. Political and business leaders across the globe have picked up the mantle energetically in the last couple of years, making ambitious pledges to plant millions, billions and trillions of new trees. As the UN Decade of Ecosystem Restoration prepares to embark in 2021, getting more trees in the ground is high on many national and international priority lists. 

In a surprising twist (which is perhaps more of a testament to the small world of peatland science), Center for International Forestry Research (CIFOR) principal scientist Daniel Murdiyarso had his own small role in the Flow Country afforestation project. Murdiyarso is now one of the foremost living experts on the peatlands of his home country, Indonesia, but did his PhD at the University of Reading in the 1980s. There, he was tasked with, among other things, testing different provenances of lodgepole pine to see which might thrive best in the Flows. The disastrous outcome of the project became particularly apparent to him in 2019, when he attended an IPCC [Intergovernmental Panel on Climate Change] meeting in Edinburgh. “We went on a field trip to look at some of those plantations,” he recalls, “and the forests there just look so sad!”

Indonesia has an estimated 22.5 million hectares of peatlands, and Murdiyarso has been working hard to prevent peatland developers from making similar mistakes. He and his colleagues encourage foresters to plant native species rather than exotic ones and to choose a mix of species rather than a monocrop. He says it’s also important to select species that suit the ecosystems’ high water tables wherever possible – such as the spiky-leaved sago palm [Metroxylon sagu], a valuable export crop as well as source of a local staple starch. 

Given the carbon-storage and biodiversity values of peatlands, there are also distinct advantages to simply leaving them be, though Murdiyarso highlights that it’s critical to create clear legal frameworks that maintain community access and defend against encroachment. “You need to make it a defined protected area, but you don’t want to fence it, either,” he says. “You still need to let people in to make use of it – to get benefits from it, but not own it. That’s the real challenge.”

In the Congo Basin – where sits the world’s largest tropical peatland complex, the Cuvette Centrale – the challenge of balancing protection and use is particularly pressing. The peatland swamp forests there are extremely isolated and as of yet are relatively intact. “So it’s a case of looking at the degradation in places like Indonesia and trying to prevent that before it happens,” says Greta Dargie, a scientist at the University of Leeds and one of the researchers who first mapped the full extent of the Cuvette Centrale in a groundbreaking 2017 study. 

Currently, the biggest risk to those peatlands is hydrocarbon exploration, which could lead to draining and drilling in or around the Cuvette Centrale, and would be disastrous for the ecosystems’ resilience and carbon storage capacity. “The two governments [Republic of Congo and Democratic Republic of Congo] have said that they don’t want to degrade the peatlands; they want to protect them,” says Dargie. “But then, obviously, within each country there are different groups who have different ideas about their nation’s future,” she says. “So it’s still unclear what’s going to take priority: preserving the peatlands, or potential economic gains through other development pathways.”

Dargie says it’s possible that falling oil prices, the COVID-19 pandemic and the lack of infrastructure in the Cuvette Centrale could put the brakes on extractive ambitions, at least temporarily. In the meantime, scientists from the chilly Scottish highlands to the steamy Congolese rainforests continue to toil through mud and midges to discover, evaluate and communicate what these strange, rich and delicate ecosystems have to offer, while they’re still intact enough to do so. They’re also exploring what kinds of plants we might cultivate in peatlands – both to aid restoration and to contribute to food security and livelihoods – without destroying their precarious balance of water and soil, and lifting the lid on crucial carbon-storage sites in the process.