These Trees Are Spreading North in Alaska. That’s Not Good
White spruce trees are expanding into the Arctic tundra with stunning speed, with potentially serious consequences both for the region and the world.
wired.com

Thawing permafrost is the aspect of Arctic greening that concerns scientists the most. These frozen soils are loaded with dead organic matter that hasn’t fully decomposed, but will decay rapidly once it thaws. Microbes then begin munching on the material, spewing both carbon dioxide and methane, an extremely potent greenhouse gas. Permafrost is now thawing so fast that Arctic land is collapsing, gouging great big holes in the landscape. “The implications are significant,” says Goetz. “It always comes around to the permafrost in the end, because that’s the big carbon reservoir that’s being mobilized.”