Lichens
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History of Recording
Usnea articulata
Photo: Bryan Edwards
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Dorset is a small lowland county that has been relatively well recorded for lichens.
The earliest lichen record by William Stonestreet in 1717 is of the spectacular
beard lichen Usnea articulata, for which the western part of the county
is a national stronghold.
Until the 1880s there are appears to be very few records apart from the few
resident naturalist’s such as Richard Pulteney, J.C. Dale and G. Lister. From
the mid-1880s to 1906 E.M. Holmes collected many notable species from the Isle
of Portland and from the Studland and Swanage area, adding many new species to
the county. Many of his specimens are in Dorchester Museum. He prepared a
manuscript lichen flora for the county that was never published.
There followed a lull in activity until the late 1950s when Dr Humphry Bowen
began recording in the county. Shortly afterwards Mr Peter James from the
Natural History Museum and Dr Francis Rose started surveying a number of
parkland and woodland sites including the internationally important Melbury Park.
In 1976 Humphry Bowen published the first modern lichen flora and listed 497
species. By the time he published the
Flora of Dorset
in 2001 the number of species had increased to 658. The current total for the
county is 710, 38% of the UK flora, of which 20 are presumed to be extinct and 6
are dubious or erroneous records.
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The Lichen Flora
Number of lichens recorded by 10 km
square in Dorset, February 2005
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The lichen flora is very diverse for a lowland county, which can in part be
explained by the low levels of atmospheric pollution and the very wide variety
of habitats present. However, the lack of upland areas, hard acid rock outcrops
and the relatively low rainfall means than more western counties such as Cornwall
and Devon support many species not found here.
Those habitats in Dorset that are important for lichens include:
- Ancient woodland
- Ancient parkland
- Wayside trees
- Lowland heathland
- Limestone rocks and soil
- Chalk grassland
- Soft cliffs
- Coastal rocks
- Sarsen stones
- Churchyards
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Changes in the Lichen Flora
Candelaria concolor (yellow) and
Punctelia borreri
(grey),
two lichen species spreading in the county due to changes
in temperature
and levels of ammonia and nitrogen.
Photo: Bryan Edwards
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Squamarina cartilaginea
Photo: Bryan Edwards
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Lichen are quite rightly thought of as slow growing organisms requiring stable
or ancient habitats. However, over the past decade there have been very dynamic
changes in the lichen flora of the county and of southern England generally.
Although the precise factors are not fully understood, declining sulphur dioxide
levels, an increase in ammonia and nitrogen pollution and climate change are all
thought to be playing a part. Recently described nitrogen-demanding species such
as Bacidia adastra and Lecanora barkmaniana have been found in the
county, and species thought to be uncommon such as Candelaria concolor,
Flavoparmelia soredians and Punctelia borreri have increased
significantly, probably due to increases in nitrogen levels and temperature.
There have been relatively few recent extinction’s in the county, the last being
Caloplaca luteoalba which was restricted to old Elm trees and was last seen
in 1975. However, there are a significant number of species that are restricted to
just one or two sites and require careful monitoring.
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Who To Contact
If you would like to send in your lichen records, or for further
information on how you can become involved, please contact:
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Dorset Environmental Records Centre