In summer of 2019, Roman Dial and his friend Brad Meiklejohn rented a single-engine plane in Kotzebue on the northwest coast of Alaska. Even those wings could only get them a five-day hike from where they wanted to be: deep in the tundra, where Dial had noticed peculiar shadows appearing in satellite images.
On the fourth day of this hike, the pair were walking along a caribou trail when Meiklejohn yelled, “Stop!” Dial thought his friend had seen a bear. But it was something more troubling: a stand of white firs. The plants were well formed and at chest height, like little Christmas trees. And from a planetary perspective, they were bad news, because they weren’t where they needed to be at all. In this Alaskan tundra, fierce winds and bitter cold favor shrubs, grasses, and grass-like sedges. The growing season is supposed to be too short for the trees to become established, 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. As the Arctic warms more than four times faster than the rest of the planet, this is bringing down the ecological barriers for plants in the far north, and more vegetation is heading poleward. “The next day we found more and more as we headed east, until we discovered an Arctic white spruce savannah,” recalls Dial, an ecologist at Alaska Pacific University. “That sounds fun to say, it might have been the most exciting field trip I’ve ever been on.”
Arctic Green is a warning light on the climate damage dashboard, both for the region and the world at large. Proliferating shrubs are one thing – they are small and grow relatively quickly – but long-lived white spruce is another thing entirely. “When you see trees growing, you know the climate has really changed,” says Dial. “It’s not like five years of time, or 10 years of time. It’s 30 years of climate that have established new trees in new places.”
Write this month in the magazine Nature, Dial and his colleagues put hard numbers on what they discovered in the Alaskan tundra: White spruce, both as individuals and as a population, is growing exponentially there. The population is now moving north at a rate of 2.5 miles per decade, faster than any other conifer treeline scientists have measured, in what must be one of the most inhospitable places on the planet to to a tree
