LICHENS
Changes in the lichen flora on trees in Epping Forest through periods of increasing and
then ameliorating sulphur dioxide air pollution
Prof. David L. Hawksworth* and Dr. Paulette M. McManus
* International Mycological Institute, Ferry Lane, Kew. Surrey TW9 3AF
Introduction
The lichen flora of, or more correctly the lichen-forming fungi known from. Epping Forest are of
considerable scientific interest. This interest derives not so much for the species now present, but
rather because of the documentation available on the changes which have taken place over the last
200 years in an essentially stable woodland system. No other single site in the British Isles has a
comparable history of in-depth studies extending over such an extended time scale. The closest
long-term record to it is probably that of Gopsall Park. Leicestershire, but there many trees have been
lost and there are long periods in which no studies were carried out (Sowter & Hawksworth, 1970).
In the case of Epping Forest, its overall structure appears to have remained essentially the same
throughout the period of the flora record. However, since the Epping Forest Act of 1878. pollarding
almost ceased so that the trees have grown on to form denser canopies in many areas than was formerly
the case. Nevertheless, a considerable number of trees, and most conspicuously those of Fagus
sylvatica in High Beach and of Quercus robur south of Queen Elizabeth's Hunting Lodge, are much
older than 400 years. Consequently, trees that would certainly have been mature specimens last century
abound. Indeed, many trees available for examination today can be assumed to be the same trees
studied by the early investigators of the Forest's lichens.
This contribution updates the lichen record and reviews the history of lichenological investigations
in Epping Forest, emphasizing the changes which have taken place in the species present on trees over
the last 200 years. Overtime, 145 species of lichens have been recorded from trees in the Forest. The
present lichen record lists 41 species.
History Of Investigations
The first student of Epping Forest lichens was Edward Forster jr. (1765-1849) who grew up in
Walthamstow. A few of Forster's records were published in Turner & Dillwyn (1805), but the richest
source of his records are his notebooks and specimens, all preserved in The Natural History Museum.
London (BM). He recorded 65 species on trees (Crombie, 1885), evidently mainly in the period
1784-96, His contributions are discussed in detail by Crombie (1885) and Laundon (1967). and some
of his records are also cited in Laundon (1970). Forster's reports are not always easy to localize. Those
from "Walthamstow", with no further details, which are of species that would have been expected to
be also then present in Epping Forest are included in Appendix 1, as are ones from close-by or in the
then area of the Forest (e.g. Hale End). Species recorded from Hainault Forest are not, however,
incorporated in the Appendix as this area is not now treated as a part of Epping Forest.
The Rev. J.M. Crombie (1830-1906) made repeated visits to the Forest in 1865-8. and some records
from these excursions were included in Crombie (1870). Following visits in 1881-2, he prepared a
comprehensive account of the lichen flora, paying particular attention to the causes of the declines in
species number and luxuriance which he found had taken place since his first series of visits. In total,
from all habitats, Crombie catalogued 171 species, of which 86 were still present on trees in his 1881-2
survey. Crombie's collections are preserved in BM.
Crombie (1885) recognized it would be"... interesting to the lichenist of the future, some 50 or 100
years hence, to compare the above list with those that the Forest may then present". This challenge
was taken up by Mr R.A. Paulson (1857-1935) and Mr P.G. Thompson (1866-1953), who in a series
of papers (Paulson & Thompson, 1911,1913, 1919). reported 129 taxa from a wide range of habitats,
including extensive notes on ecology (see also Paulson, 1918) and distribution. Records from visits
are included on cards at the Epping Forest Conservation Centre. Their records extend from 1909-26.
and their specimens are now in the Passmore Edwards Museum in Stratford (PEM); some collections
were also given to the Epping Forest Museum in Chingford (EFM).
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