Boreal tree canopies keep permafrost carbon frozen, cutting summer thaw by a metre
Researchers found that dense northern forest canopies shade the ground enough to keep permafrost about one metre deeper than in treeless areas, preserving roughly 59 billion tonnes of carbon.
By combining satellite imagery, mapping data and climate modelling, researchers showed that boreal forest canopies act as large sunshields, limiting the depth of summer permafrost melt by roughly one metre across sixteen northern regions. This shading preserves an estimated 59 petagrams of carbon in frozen ground, equivalent to about one-third of the carbon stored in permafrost soils. The finding, reported in Nature Climate Change, fills a major gap in climate-system understanding, as previous assessments counted only carbon in living trees.
The team warned that rising temperatures, intensified wildfires and deforestation could remove this protective layer, allowing microbes to decompose thawed organic matter and emit carbon dioxide and methane. In addition, the canopy helps prevent land-surface collapse that could wash away another 19 petagrams of carbon. Protecting the taiga therefore represents a crucial natural brake on a potential climate feedback loop.
Why it matters
The forest shade prevents massive carbon release from permafrost, a key factor in limiting future climate warming.
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