Rising summer temperatures have triggered an arboreal facelift across a vast swath of Eurasian tundra, transforming patches of Arctic prairie into forest much faster than scientists ever thought possible.

Instead of trees slowly invading from the south over the course of centuries, stands of existing dwarf willows and alders have responded to the changing climate on their own — growing up and branching out into groves of small trees during mere decades, according to a new detailed analysis published this week in the journal Nature Climate Change.

“It’s a big surprise that these plants are reacting in this way,” said lead author Marc Macias-Fauria, with Oxford University’s Department of Zoology and the Oxford Martin School, in this story posted by Oxford.

The study is part of a growing body of research into the terra-forming of the Arctic by climate change, with scientists across the world documenting the dramatic spread of shrubs and trees into formerly low-growing tundra on a scale not seen in thousands of years.

During the past 4,000 years, there was a long-term cooling — referred to as neoglaciation — which is responsible for the nature of the forest-tundra today. Previously, tree populations were more abundant in the forest tundra of northern Québec. As the climate cooled, the trees reverted to shrub form but no longer reproduced. Fires eliminated some, and since there was no reproduction, the region attained its present-day character.

Now, as the climate is warming, krummholz in place will expand, grow and reproduce. Thus, there is a large area where trees can colonize, suggesting the treeline can move rapidly northward. The long-distance transport of seeds across northern Canada will also enable rapid migration.

However, the relative impact of climate warming and increased fires needs to be accounted for. Thus, present warming of northern Canada will impact the northern vegetation in a complex way, with different regions responding differently, and with some processes occurring rapidly, and others with long time lags.