Trees colonising formerly open tundra as the climate warms could cause Arctic ecosystems to release vast amounts of stored soil carbon into the atmosphere, a new paper argues. Many climate models have assumed that trees taking over the Arctic, and the enormous increase in plant biomass this would bring, would cause these landscapes to absorb much more carbon than they did before, helping restrain the effects of climate change. But this study suggests that’s far from certain. In Scandinavia at least, when tundra heath turns into birch woodland it seems it could release much of the carbon stored in the soil into the air. This will more than counterbalance the fact that a forest holds around twice as much carbon in its biomass. So far from holding climate change in check, accelerated tree growth, and colonisation of treeless landscapes, could speed it up.
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Would more trees in the Arctic absorb carbon, or cause more to be released?
