Boreal forest canopies keep 59 billion tonnes of permafrost carbon frozen by reducing summer thaw depth by one metre

A new study in Nature Climate Change finds that boreal forests act as natural sunshields for permafrost. Researchers from Humboldt University, the Alfred Wegener Institute, the University of Oslo, and Vrije Universiteit show that tree canopies reduce summer soil thawing by about one metre compared to open land. This shading effect keeps roughly 59 billion tonnes of carbon locked in frozen ground that would otherwise decompose and release greenhouse gases. The finding highlights a natural service that standard climate models have not accounted for. Without the canopy cover, permafrost thaws deeper in summer, exposing ancient organic matter to microbes that produce carbon dioxide and methane. The study suggests that large-scale deforestation or fire-driven canopy loss in boreal regions could accelerate permafrost thaw and create a significant new source of emissions. For carbon markets and climate policy, this means boreal forest protection has a direct, measurable impact on preventing carbon release. Preserving canopy cover in northern forests is not just about timber or biodiversity. It is a concrete way to avoid unlocking a massive frozen carbon stock that would be extremely difficult to recover once lost.