Lichens

The lichenologist Dr Francis Rose, former lecturer at King’s College, London, had scratched his head over closed canopy theory from the 1970s until his death in 2006. His work is largely concerned with epiphyte forest lichens and for thirty years he studied them, in particular, in the New Forest. He noticed that very few species of lichen – or, indeed, mosses or liverworts – could be found inside dense stands of trees. Almost all require light and are found on either open grown trees or trees along rides and the edges of glades or ‘lawns’. 

The survival of relict species of moss and arctic alpine plants – typical of the habitat of the last glacial period (i.e. before trees returned to our landscape with the warming climate) – on common land in Denmark grazed by horses also convinced Rose of the role of herbivores in keeping areas open of tree cover. Similar Devensian era habitats in Norfolk, he noted, were vanishing with the abandonment of traditional grazing, and small fen plants like northern bog sedge and butterwort, and various orchids and subarctic type bryophytes were disappearing with them. 

He wrote enthusiastically to Vera after reading his ‘landmark’ book in 2000: ‘It covers in a masterly way all of the points that have made so many of us very doubtful about the ‘classic’ hypothesis, namely that the temperate forests were very dense closed canopy in pre-history.’