Global warming changes tundras into forests much faster than anyone expected

Well, we knew this was going to happen eventually - but now scientists are actually seeing it with their own eyes. Researchers from Finland and Oxford University have discovered that large swaths of European and Asian arctic tundra 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.

The specific area in question is a 100,000 km2 region known as the northwestern Eurasian tundra stretching from western Siberia to Finland. By using satellite imaging, field research, and interviews of indigenous reindeer herders, 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.

And what's particularly alarming to the scientists is how fast it's happening. From Oxford's press release:

"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 colonised 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 fear that 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 albedo effect, which is the amount of sunlight reflected by the surface of the Earth. 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, titled "Eurasian Arctic greening reveals teleconnections and the potential for novel ecosystems", was published in the journal Nature Climate Change.

Image via BC Forbes.