In the last few decades, shrubs in the Arctic tundra have transformed themselves into trees as a result of the warming Arctic climate, at a speed and magnitude that is far greater than scientists had ever anticipated. If this continues and is replicated across the whole of the Arctic tundra, it would significantly accelerate global warming.
A report published in the journal Nature Climate Change entitled “Eurasian Arctic greening reveals teleconnections and the potential for novel ecosystems” detailed research led by scientists from the University of Lapland, Finland, and Oxford University England. The scientists investigated an area of around 100,000 square kilometres known as the northwestern Eurasian tundra, which stretches from western Sibera to Finland. Surveys of the vegetation, using data from satellite imaging, fieldwork, and expert observations from indigenous reindeer herders, showed that, in 8-15% of the area, willow (Salix) and alder (Alnus) plants have grown into trees over 2 metres in height in the last 30-40 years.
Models made previous to this research had indicated that the potential impact of forestation in the Arctic tundra could increase Arctic warming by an extra 1 to 2 degrees Celsius by the late 21st Century.
“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 increase to the Arctic warming comes as the increase in forest decreases the albedo effect in the region. During the Arctic spring and autumn, much of the flora is hidden underneath a blanket of white, light-reflecting snow. However, trees are tall enough to break the snow cover and are dark enough to start absorbing the light (i.e., heat). This increased absorption of the Sun’s radiation, combined with microclimates created by forested areas, adds to global warming: making an already-warming climate warm even more rapidly.
“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,” said 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.”