Boreal forests shade permafrost so effectively that summer thaw stays about one metre shallower

Spruce and birch trees are seen tilting along the edge Stevens Pond on the University of Alaska Fairbanks campus on Sept. 18, 2022. Thick green tree canopies across northern forests act as giant sunshields, keeping permafrost cool enough to hold 59 billion tonnes of carbon safely in the ground.The discovery reveals that the forest canopy reduces summer soil thawing by roughly one metre compared to open, treeless land. By shading the surface, boreal trees prevent vast amounts of ancient organic matter from rotting and leaking greenhouse gases into the air.The international study, published in Nature Climate Change, shows an essential natural service that standard climate models have long missed. Researchers from Humboldt University of Berlin, the Alfred Wegener Institute (AWI) in Potsdam, the University of Oslo, and Vrije Universiteit Amsterdam led the project.Hidden carbon beneath the rootsFor decades, environmental scientists measured the carbon stored in northern forests mainly by counting the wood, leaves, and roots of living trees. Living trees across frozen northern regions store between 7 and 19 petagrams (gigatonnes) of carbon in their wood and leaves.However, the team disco...