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Not all environments benefit from afforestation, say researchers.
In the face of rising carbon emissions, one solution often gets touted: planting more trees. More forests can only mean more carbon dioxide is taken out of the atmosphere. Right?
Well, not in every instance, according to researchers from Aarhus University.
In a paper published in Nature Geoscience, the Danish researchers, along with colleagues from the University of Cambridge, state that the Arctic is particularly unsuitable for afforestation.
The normally tree-free tundra already stores a vast resource of carbon within its soil. The researchers say any new forests could disrupt this delicate carbon sink and indirectly release more carbon than they would absorb.
Arctic new trees
“Soils in the Arctic store more carbon than all vegetation on Earth,” Jeppe Kristensen, an assistant professor of ecoinformatics and biodiversity at Aarhus University and lead author of the study, said in a statement.
In the paper, Kristensen stressed that such Arctic soils are vulnerable to disturbances from cultivation and agriculture. These developments would also reduce the tundra’s snow coverage, which, unlike green and brown trees, reflects much of the sun’s light and heat.
Any new forests planted in the higher latitudes of North America, Scandinavia and Asia also risk the wrath of wildfires, which have become increasingly severe as global temperatures have increased.
Kristensen says new, well-meaning forestry projects should heed these warnings and appreciate that planting trees is not a one-size-fits-all policy.
“There are projects in many areas of the Arctic and the boreal zone, including the ones we mention in Greenland, Alaska and Iceland,” Kristensen told Technology Networks. “Such initiatives can be driven by different well-meaning targets. NGOs [non-governmental organizations] that want to accelerate the green transition, governments that want to become timber self-sufficient, landowners trying to make a profit while contributing to solving the climate crisis.”
“While all are respectable and totally legitimate goals, most projects are at least partly motivated by climate change mitigation. Therefore, it is important to clarify that planting trees – just like most other nature-based solutions – is not a one-size-fits-all solution. In the wrong places, it can do more harm to the climate than good, and in those cases forestry should be viewed as any other production system, and hence compensate for the harm it causes. Not just to climate, but also local biodiversity and livelihoods.”
Kristensen’s warnings follow recent research showing that the boreal forests of Alaska are already growing farther north. Published in Nature in 2022, the research estimated that the North American white spruce tree population is doubling in size with each passing decade, encroaching into the Arctic tundra as global temperatures rise.
To preserve as much of the Arctic’s stored carbon as possible – and help halt the spread of such new forests – Kristensen and his colleagues propose that local communities could support sustainable populations of large herbivores, such as caribou, which would graze the land, keeping tree seedlings in check.
“The mechanisms causing the cooling effects are a consequence of what the animals do on the landscape, which is not necessarily species specific,” Kristensen told Technology Networks.
“Hence, if animals are missing, I would certainly encourage introductions of native herbivores like caribou/reindeer and musk oxen, which is already happening in many areas of the Arctic. However, I would also like to see controlled experiments with introductions of more complex assemblies of animals, for instance including horses, bison, and perhaps even furry camels. Particularly bison and horse were common in the Arctic during the last ice age, and hence are an intrinsic part of these ecosystems on evolutionary timescales.”
Reference: Kristensen JÅ, Barbero-Palacios L, Barrio IC, et al. Tree planting is no climate solution at northern high latitudes. Nat. Geosci. 2024. doi: 10.1038/s41561-024-01573-4
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Science Writer & Editor
Leo is a science writer with a focus on environmental and food research. He holds a bachelor’s degree in biology from Newcastle University and a master’s degree in science communication from the University of Edinburgh.
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