Warming climate sees tundra turn to forest

4 June 2012

In just a few decades shrubs in the Arctic tundra have turned into trees as a result of the warming Arctic climate, creating patches of forest which, if replicated across the tundra, would significantly accelerate global warming.

Scientists from Finland and Oxford University investigated an area of 100,000 km2, known as the northwestern Eurasian tundra, stretching from western Siberia 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.

Previous models assessing the potential impact of forestation have suggested that the advance of forest into Arctic tundra could increase Arctic warming by an extra 1-2 degrees Celsius by the late 21st Century.

A report of the research is published in the journal Nature Climate Change.

‘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 change from shrubs to forest is important as it alters the albedo effect – the amount of sunlight reflected by the surface of the Earth.

In the Arctic spring and autumn much of the time shrubs are covered under a blanket of white, light-reflecting snow. In contrast, trees are tall enough to rise above the snowfall, presenting a dark, light-absorbing surface. 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.’

For more information contact Dr Marc Macias-Fauria on +44(0)1865 281878 or email marc.maciasfauria@zoo.ox.ac.uk

Alternatively contact the University of Oxford Press Office on +44 (0)1865 283877 or email press.office@admin.ox.ac.uk

Notes to editors

  • A report of the research, entitled ‘Eurasian Arctic greening reveals teleconnections and the potential for novel ecosystems’, is published in the journal Nature Climate Change, 3 June 2012.
  • The Finnish-UK team was led by Professor Bruce Forbes of the University of Lapland, Finland.
  • An image related to the story is available here [Credit: BC Forbes]: http://www.ox.ac.uk/images/hi_res/14780_Arctic_tundra_trees.jpg

    Caption: View of the the northernmost foothills of the Polar Ural mountains on the southern Yamal Peninsula in West Siberia, Russia. Here willow (Salix lanata) thickets and individuals have a greyish metallic canopy and stand out in the forefront and background, located mostly in concave areas. Alder (Alnus fruticosa), with a dark green canopy, stands out clearly against both willow and the other tundra vegetation. An increase in shrub height in recent decades has been remarked upon by indigenous Nenets nomads both east and west of the Urals, who have had to modify their reindeer herding practices in response to the changes. Photo: BC Forbes.
  • About the Oxford Martin School:

    The Oxford Martin School is a unique, interdisciplinary research community of over 300 scholars working to address the most pressing global challenges and opportunities of the 21st century. Founded at the University of Oxford in 2005 through the vision and generosity of Dr James Martin, the Oxford Martin School has grown into a global centre for interdisciplinary scholarship and thinking about the future. The School aims to develop new approaches to some of society’s most intractable questions. Research is organised via four core themes: health and medicine; energy and environment; technology and society; and ethics and governance. The Oxford Martin School’s Director is Ian Goldin, University Professor of Globalization and Development. http://www.oxfordmartin.ox.ac.uk