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Rapid climate change is upending plant life in the Arctic. A new in Nature shows how one of the most fragile ecosystems on Earth is changing as warming is up to four times faster in the Arctic than on Earth on average. Scientists around the world have been studying the biological changes in more than 2,000 experimental plots in the northern polar region for 40 years.

"Changes in vegetation are an early warning signal that the entire ecosystem will change, with consequential effects on wildlife, humanity and Earth's natural ability to store carbon," says Anne Bjorkman, researcher in plant ecology at the University of Gothenburg.

Extensive changes

The results of the study do not give clear results on which plant species are favored at the expense of others. But the researchers are certain that the treeless mountains and mountain meadows will change in appearance.

"The change in what grows on a site is extensive, with new species appearing and/or existing species disappearing on almost 60% of the experimental plots. There are many factors that determine how plant life changes at a particular site, such as how wet the soil is, or how windy it is. This affects the microclimate that plants experience.

"In general, we see that shrubs benefit from a longer growing season, they simply steal the sunlight from species with a low growth habit," says Robert Bjork, researcher at the Arctic Ecosystem at the University of Gothenburg.

Evergreen plants are winners

Evergreen plants such as lingonberries and crowberries, as well as some summer green plants such as willow bushes, will also have a competitive advantage when snow covers the ground fewer days a year in the Swedish mountains. Many plants on the tundra are low-growing to withstand strong winds, and if it gets warmer, more species can become established, increasing biodiversity in some places.

"But where the shrubs take over, biodiversity will decrease, and then the question is where the outcompeted species will go. There are no colder regions than the Arctic, and some species may disappear completely from large areas," says Bjorkman.

The unique vegetation of the Arctic tundra is important for carbon sequestration and how much sun is reflected from the ground surface. Larger shrubs absorb more of the sun's rays than today's vegetation, which amplifies the warming of the Arctic.

"Changes in vegetation obviously also affect herbivorous animals. Reindeer husbandry cannot have the same grazing areas in the valleys as today, perhaps they can find new ones on the bare mountains. Then tourism will be affected when mountain birches and shrubs take over on the mountains and the alpine meadows with beautiful wildflowers disappear. And it will be difficult to get hold of drinkable water when the glaciers and the late snowfields melt away," says Robert Bjork.

The researchers cannot give a clear picture of exactly how the Swedish mountain world will look in 50 to 100 years. Much research remains to be done to find out, but it is certain that the area of open mountain meadow will decrease. At the Latnjajaure research station near Abisko, led by the University of Gothenburg, the changes are clearly visible.

"We are in the midst of climate change and will reach certain thresholds where the flora will change radically, but we don't know when it will happen. Or how it will happen," says Bjorkman.