If you happen to be walking in the Lake District and see an unusual type of lichen that has been stapled to an oak it will be tree lungwort (Lobaria pulmonaria).
Transplanting lungwort from old fallen oaks to younger standing trees by stapling, or using glue and mesh to hold them on, is an attempt by the National Trust to prevent the species dying out.
This is one of the UK’s largest lichens and was once common. A healthy specimen is lush and green when wet and is formed of a fungus and two sorts of algae, green and blue-green. Its name derives from the fact that fully grown it looks like a pair of lungs and was once used as a medicinal herb to treat breathing problems. It is ironic that a plant with such a name is being killed off by air pollution. It has died out in most of Europe, with acid rain and poor air quality the main causes.
Now it is a rarity in Britain and confined to the west of Scotland, Wales, and with remnants in the Lake District. There are occasional patches in other places such as the New Forest but pollution prevents sexual reproduction. When lungwort starts to thrive again we will know we are all breathing cleaner air.