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Tundras transforming into forest much faster than presumed

Researchers from Finland and Oxford University have come across large swaths of European and Asian arctic tundra which are quickly turning into forests. They're attributing it to climate change, but what's worse is that the trend could significantly accelerate global warming should it spread across the entire tundra.

Arctic tundra occurs in the far Northern Hemisphere, north of the taiga belt. The word "tundra" usually refers only to the areas where the subsoil is permafrost, or permanently frozen soil.
A 100,000 km2 region known as the northwestern Eurasian tundra stretching from western Siberia to Finland is the area of concern. The researchers discovered that certain trees have grown over two meters in height over the last three to four decades across 8-15% of the studied area availing satellite imaging, field research, and interviews of indigenous reindeer herders.

And what's particularly alarming to the scientists is how fast it's happening. "It's a big surprise that these plants are reacting in this way," said Dr Marc Macias-Fauria of Oxford University's Department of Zoology and the Oxford Martin School, first author of the paper.

"Previously people had thought that the tundra might be colonized by trees from the boreal forest to the south as the Arctic climate warms, a process that would take centuries. But what we've found is that the shrubs that are already there are transforming into trees in just a few decades."

"The speed and magnitude of the observed change is far greater than we expected," said Professor Bruce Forbes of the Arctic Centre, University of Lapland, corresponding author of the paper.

The scientists are apprehensive about the potential impact of forestation could increase Arctic warming by another 1-2 degrees Celsius by the late 21st Century. It's believed that the change from shrubs to forests will alter the Earth's reflection coefficient. Because trees are tall enough to rise above the snowfall, they'll be able to absorb the incoming light unlike snow covered shrubs. This increased solar absorption, say the scientists, combined with microclimates created by forested areas, will increase the rate at which global warming is happening.

"Of course this is just one small part of the vast Arctic tundra and an area that is already warmer than the rest of the Arctic, probably due to the influence of warm air from the Gulf Stream," noted Dr Macias-Fauria. "However, this area does seem to be a bellwether for the rest of the region, it can show us what is likely to happen to the rest of the Arctic in the near future if these warming trends continue."

The Oxford-Finnish collaboration study "Eurasian Arctic greening reveals teleconnections and the potential for novel ecosystems", was published in the journal Nature Climate Change.