Planting trees in high Arctic latitudes could accelerate rather than slow global warming, scientists say

Because trees have the ability to store large amounts of atmospheric carbon, tree planting has been widely touted as a cost-effective way to reduce global warming. But an international group of scientists, writing in the journal Nature Geoscience, argues that planting trees at high latitudes will accelerate global warming rather than slow it down.

As the climate warms, we can plant trees farther and farther north, and large-scale reforestation projects in the Arctic have been supported by governments and businesses as a way to mitigate the worst effects of climate change. .

But if trees are planted in the wrong places, such as in normally treeless tundra or swamps, or large areas of boreal forests with relatively open tree canopies, they can make global warming even worse.

Lead author Jeppe Christensen, assistant professor at Denmark’s Aarhus University, said the unique characteristics of arctic and subarctic ecosystems make them less suitable for climate mitigation reforestation.

“Arctic soils store more carbon than all the plants on Earth,” Christensen says. “These soils are vulnerable not only to cultivation for forestry and agriculture, but also to disturbances such as encroachment by tree roots. Semi-continuous sunlight in spring and early summer, when snow is still on the ground, also disrupts the energy balance. ” This area is very sensitive to surface darkening because green and brown trees absorb more heat from the sun than white snow. ”

Additionally, regions around the Arctic in North America, Asia, and Scandinavia are prone to natural disasters such as wildfires and droughts that deplete vegetation. Climate change will make these disruptions more frequent and severe.

“This is a dangerous place for trees, especially as part of a homogeneous plantation that is susceptible to such disturbances,” Christensen said. “The carbon stored in these trees is at risk of fueling disturbances and being released into the atmosphere within decades.”

The researchers say that planting trees at high latitudes is a prime example of a climate solution that can have the desired effect in some situations, but the opposite effect in others.

“The climate debate is very carbon-focused, because the main way humans have modified the Earth’s climate over the last century is through greenhouse gas emissions from burning fossil fuels,” Christensen said. said. “But fundamentally, climate change is a result of how much of the sun’s energy that enters the atmosphere stays and how much of it is released again – the Earth’s so-called energy balance.”

Greenhouse gases are one of the key factors that determine how much heat can escape from Earth’s atmosphere. However, the researchers say that at high latitudes, how much sunlight is reflected back into space without being converted to heat (known as the albedo effect) is more important than carbon storage for the overall energy balance. are.

Researchers are calling for a more comprehensive look at ecosystems to identify truly meaningful nature-based solutions that do not compromise the overall goal of slowing climate change.

“A holistic approach is not only a richer way to look at the climate impacts of nature-based solutions, it is essential to making a difference in the real world,” said lead author Mark Macias. Professor Fauria said. Scott Polar Institute, University of Cambridge.

However, researchers acknowledge that there may be other reasons for planting trees, such as wood self-sufficiency, which do not come with the bonus of climate mitigation.

“Forestry in the Far North should be considered like any other production system and compensated for its negative impacts on climate and biodiversity,” said Macias Fauria. “You can’t have your cake and eat it too, and you can’t fool the planet. By touting northern reforestation as the solution to climate change, we are only fooling ourselves.”

So how can we mitigate global warming in high latitudes? Researchers believe that working with local communities to support sustainable populations of large herbivores such as caribou could help in the Arctic and subarctic regions. It suggests that nature-based solutions to climate change may be more viable than planting millions of trees.

“There is good evidence that large herbivores affect plant communities and snow conditions, ultimately leading to cooling,” Macias Fauria said. “This happens both directly by keeping the tundra landscape open and indirectly through the influence of winter foraging by herbivores. Herbivores modify snow and its insulating capacity. , lowering soil temperatures and thawing permafrost.”

Researchers say it is important to consider biodiversity and local community livelihoods when pursuing nature-based climate solutions.

“Large herbivores have the potential to reduce climate change-induced biodiversity loss in Arctic ecosystems and remain a fundamental food resource for local communities,” said Macias Fauria. .

“Biodiversity and local communities are fundamental to nature-based solutions, not added benefits. Nature-based solutions must be led by communities living on the front lines of climate change. yeah.”