These trees spread northward in Alaska. This is not good

In summer In 2019, Roman Dial and his friend Brad Meiklejohn rented a single-engine bush plane in Kotzebue on Alaska’s northwest coast. Even those wings could only get them where they wanted to be within a five-day trek: deep in the tundra, where Dial had noticed strange shadows appearing on satellite imagery.

On the fourth day of this hike, the pair were walking along a caribou trail when Meiklejohn called out, “Stop!” Dial thought his friend had seen a bear. But there was something more unsettling: a stand of white spruce. The plants were shapely and chest-high, like little Christmas trees. And from a planetary perspective, they were bad news because they weren’t where they were supposed to be at all. In this Alaskan tundra, high winds and biting cold favor shrubs, grasses, and grass-like sedges. The growing season is said to be just too short for trees to take root, even if their seeds manage to fly north.

The trip confirmed what Dial suspected, that the shadows in the satellite images were actually misplaced trees, part of a phenomenon known as arctic greening. As the Arctic warms more than four times faster than the rest of the planet, it lowers ecological barriers for plants in the far north, and more vegetation is marching toward the pole. “The next day, as we made our way east, we kept finding more and more until we discovered an arctic savanna with white spruce,” recalls Dial, an ecologist at Alaska Pacific University. “Sounds weird to say it was maybe the most exciting hike I’ve ever done.”

A solid white spruce, probably around 60 years old.

Courtesy of Roman Dial

Greening the Arctic is a glaring warning light on the climate damage dashboard, both for the region and for the world at large. The proliferation of shrubs is one thing – they are small and grow relatively quickly – but long-lived white spruce trees are quite another matter. “When you see trees growing, you know the climate has really changed,” Dial says. “It’s not like 5 years of weather or 10 years of weather. It’s 30 years of climate that have established new trees in new places.”

Write in your diary this month Nature, Dial and his colleagues quantify what they discovered on the Alaskan tundra: White spruce grow exponentially there, both individually and as a population. The population is now moving north at a rate of 2.5 miles per decade, faster than any other conifer line scientists have measured, in what should be one of the most inhospitable places on the planet for a tree.

This one is probably five years old.

Courtesy of Roman Dial

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