As a result of much research into both early documents and field evidence, far more is now known about the history of British woodlands than was the case 25 years ago. Rackham's (1976, 1980, etc.) historical studies have been outstanding in this context. Although the percentage cover of woodlands known to be ancient in Britain is one of the lowest in Europe, the epiphytic flora, particularly of lichens, is outstandingly rich in those areas that have relatively low levels of air pollution, or none at all.