18 June 2012 Last updated at 13:29

Nature's big picture: Arctic forests

The expansion of these beautiful birch forests in Sweden's Arctic could be increasing the release of carbon into the atmosphere, say scientists. Research led by Iain Hartley from the University of Exeter showed that the forests appeared to stimulate the breakdown of organic matter in the soil - a process that releases carbon dioxide. The findings are described in the journal Nature Climate Change. The study provides evidence that contradicts the assumption that the "greening of the Arctic" is actually helping to slow carbon release, as the plants and trees absorb the greenhouse gas from the atmosphere. (The team that carried out this study included researchers from the University of Stirling, Natural Environment Research Council Radiocarbon Facility, James Hutton Institute and the University of Sheffield)