Tree planting is often presented as an effective and affordable strategy for combating global warming, thanks to trees’ ability to absorb significant amounts of atmospheric carbon. Nevertheless, a team of international scientists contends that planting trees in northern regions may actually speed up global warming instead of slowing it down. The reason? The soils in the Arctic and Subarctic harbor vast reserves of carbon that could be released into the atmosphere when disrupted, and trees absorb more sunlight and heat than the reflective white snow.
Tree planting is frequently considered a cost-effective method for combating global warming, attributed to the capacity of trees to capture large amounts of atmospheric carbon. However, an international team of researchers argues in the journal Nature Geoscience that planting trees in high-latitude regions may exacerbate rather than alleviate global warming.
As temperatures rise, it has become feasible to plant trees further north. Consequently, extensive tree-planting initiatives in the Arctic have been promoted by governments and corporations as a means to soften the harsh impacts of climate change.
However, introducing trees to inappropriate locations—like the typically treeless tundra and wetlands, or vast areas of the boreal forest with sparse tree cover—can actually worsen global warming.
Lead author Assistant Professor Jeppe Kristensen from Aarhus University in Denmark explains that the distinct traits of Arctic and sub-Arctic ecosystems make them ill-suited for tree planting aimed at mitigating climate change.
“Arctic soils store more carbon than all the vegetation on Earth combined,” noted Kristensen. “These soils are easily disturbed by activities like forestry or agriculture, as well as tree root penetration. Additionally, continuous daylight in spring and early summer—when snow remains—means that the energy balance in this area is highly sensitive to surface changes; green and brown trees capture more solar energy than the reflective white snow.”
Moreover, North America’s, Asia’s, and Scandinavia’s polar regions are susceptible to natural disturbances—such as wildfires and droughts—that destroy vegetation. Climate change is increasing both the frequency and severity of these disturbances.
“For trees, this area poses significant risks, especially as part of a uniform plantation susceptible to such disturbances,” Kristensen warned. “The carbon sequestered in these trees could potentially exacerbate disturbances, releasing it back into the atmosphere in a matter of decades.”
The researchers assert that high-latitude tree planting exemplifies a climate solution that might produce beneficial effects in one context while leading to adverse effects in another.
“Discussions on climate often focus on carbon due to the substantial impact of greenhouse gas emissions from fossil fuel combustion on our planet’s climate in the last century,” Kristensen indicated. “However, fundamentally, climate change revolves around how much solar energy stays in the atmosphere versus how much escapes—what’s known as Earth’s energy balance.”
Greenhouse gases play a vital role in determining how much heat escapes our atmosphere. However, the researchers emphasize that at high latitudes, the amount of sunlight reflected back into space (the albedo effect) is more critical than carbon storage in maintaining the energy balance.
The team advocates for a more comprehensive perspective on ecosystems to identify genuinely meaningful nature-based solutions that do not undermine the ultimate aim: mitigating climate change.
“Adopting a holistic approach not only enriches our understanding of how nature-based solutions affect the climate but is also essential for making a real-world impact,” stated senior author Professor Marc Macias-Fauria from the University of Cambridge’s Scott Polar Research Institute.
Nonetheless, the researchers acknowledge that there are other justifications for tree planting, such as achieving timber self-sufficiency, although these motivations do not necessarily aid in climate mitigation.
“Forestry in northern regions should be regarded as any other production system and should offset its negative impacts on the climate and biodiversity,” added Macias-Fauria. “We cannot have it both ways; pretending that northern afforestation solves climate issues is merely self-deception.”
So, what alternatives do we have for reducing global warming in northern latitudes? The researchers propose collaborating with local communities to support sustainable populations of large herbivores, like caribou, as a more effective nature-based strategy for climate change in Arctic and subarctic areas compared to planting massive numbers of trees.
“There is substantial evidence that large herbivores impact plant communities and snow conditions, leading to cooling outcomes,” Macias-Fauria noted. “This occurs both directly, by maintaining open tundra landscapes, and indirectly, through the behavior of herbivores in winter, which affects the snow level and decreases its insulation, lowering soil temperatures and delaying permafrost thaw.”
The researchers emphasize the importance of factoring in biodiversity and local community livelihoods when seeking nature-based climate solutions.
“Large herbivores can mitigate biodiversity loss driven by climate change in Arctic ecosystems and serve as vital food resources for local populations,” asserted Macias-Fauria. “Consideration of biodiversity and local communities is not just an added advantage but integral to nature-based solutions. Any initiatives must be led by the communities facing the direct consequences of climate change.”
