Öckinger and Nilsson (2012) have investigated the presence of lichen in 66 fragments of old-growth forest at two time-points ten years apart. They find that many individual lichen have grown and explain that by reductions in air pollution. However, lichens still disappear from the forest due to habitat fragmentation. There seems to be an extinction debt which will lead to further reduction of lichen in these old-growth forest remnants. Read the whole article in Ecology.