These trees are spreading north into Alaska. That is not good

In the summer of 2019, Roman Dial and his friend Brad Meiklejohn rented a single-engine bush plane from Kotzebue, on the northwest coast of Alaska. Even those wings were only five days away from where they wanted to be: deep in the tundra, where Dial had seen strange shadows appearing on satellite images.

On the fourth day of that walk, the couple was walking along a caribou trail when Meiklejohn yelled, “Stop!” Dial thought his friend had seen a bear. But it was something more disturbing: a clump of white spruce. The plants were well-shaped 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, fierce winds and biting cold favor shrubs, grasses and grassy sedges. The growing season would simply be too short for trees to gain a foothold even if their seeds manage to fly north.

The trip confirmed what Dial suspected, that the shadows in the satellite images were, in fact, out of place trees that are part of a phenomenon known as arctic greening. Because the Arctic is warming more than four times faster than the rest of the planet, the ecological barriers to plants in the far north are being lifted and more vegetation is marching toward the pole. “The next day we found more and more as we drove east until we discovered an Arctic white spruce savanna,” recalls Dial, an ecologist at Alaska Pacific University. “Sounds funny to say. It was quite possibly the most exhilarating walk I’ve ever taken.”

A solid white spruce, probably around 60 years old.

Courtesy of the Roman dial

Arctic greening is a bright dashboard warning light for climate damage, both for the region and the world at large. Shrub proliferation is one thing – they are small and grow relatively quickly – but long-lived white spruces are quite another. “When you see trees growing, you know the climate has really changed,” Dial says. “It’s not like five years again or 10 years again. It is 30 years of climate that has put new trees in new places.”

Writing this month in the journal Nature, Dial and his colleagues put hard numbers to what they discovered in the Alaskan tundra: White spruce is growing 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 would have to be one of the most inhospitable places on Earth for a tree.

This one is probably five years old.

Courtesy of the Roman dial