Tarnished Earth is a dramatic street gallery of photographs telling the story of the destruction of Canada's boreal forest - a continuous belt of coniferous trees separating the tundra to the north and temperate rainforest and deciduous woodlands to the south. The exhibition will be open free to anyone walking along London's South Bank for four weeks from 14 September 2010. The exhibition, which is being staged by The Co-operative, in conjunction with WWF-UK and Greenpeace , and will later tour cities across the UK, shows how the boreal forest is being flattened by the rush to extract oil from the tar sands just below its surface