The NVC (Rodwell 1991a,b, 1992, 1995, 2000) includes data from
around 35,000 vegetation samples from England, Scotland and Wales.
Although there are some gaps in the geographical coverage of these
data the maps give a general indication of the distribution of each
of the NVC types, and these NVC types can generally be related to
Annex I habitats. Guidance on the relationship between the NVC
types and the Annex I habitat types is provided.
The BRC provided data for most of the species. These data are based
on the documented occurrence of a species within 10x10 km grid
squares. This information is largely collated from local recorders
and there may be gaps in the geographical coverage of the data.
Taking account of the irregularity and incompleteness of the
recording of each species, a suitable cut-off data point was
selected for each species to ensure as far as possible that the
maps reflect contemporary distribution patterns.
For some habitats and species other, more comprehensive
distribution data were readily available, including information
held in a number of habitat-specific databases held by the JNCC
Support Unit or the country agencies. These included the Coastal
Resource, Estuaries, Saltmarsh, Sand Dune and Woodland databases
held by the Support Unit, and the Upland and Standing Water
databases held by
Scottish Natural Heritage. Some of
these databases were also able to provide information on the UK
extent of certain Annex I habitat types.
The Coastal Resource, Estuaries, Saltmarsh, and Sand Dune Databases
have evolved from resource surveys, and hold individual site and
vegetation information, which can be accessed on site,
administrative region, national or GB-wide basis (UK-wide for
estuaries). Coverage is virtually complete for these habitats. For
sea cliffs, information is only available on the length or presence
of cliffs.
The Woodland Database contains information on the distribution of
NVC woodland types which has been collated from separate surveys
undertaken by many different organisations including the country
agencies. The Upland Database holds site-based data on habitat
extent for over 300 sites distributed throughout England, Scotland
and Wales. These data are based on vegetation surveys carried out
during the 1980s and 1990s. Survey coverage of the British uplands
is incomplete and habitat data are not available for substantial
areas of upland, especially in Scotland. The Standing Water
Database contains information on 3000 lochs in Scotland, around 10%
of the total, which have been surveyed since 1983 as part of the
Scottish freshwater loch survey.
JNCC's International Designations Database (IDD) contains details,
submitted by the country agencies, of all Annex I habitats and
Annex II species recorded on designated, candidate and possible
Special Areas of Conservation in the UK. With a
few exceptions, such as vagrant sea mammals on some marine sites,
the database includes all Habitats Directive features occurring on
SACs, including non-qualifying features, i.e. non-significant
occurrences for which sites have not been proposed in a European
context. These data have been used in the production of the maps
for a number of features, where comprehensive data from other
sources were not available. However, for each SAC, only a single
central grid reference is provided in the IDD. In the case of sites
which fall within more than one 10x10 km grid square, it is
possible that the mapped feature actually lies in an adjacent
square to that shown, and/or that it occurs in more squares than
are shown on the map.
Data for offshore marine features has been collated by JNCC's
Offshore Natura Project.
Other data have come from both published and unpublished sources.
In many cases where comprehensive survey data have been
unavailable, extent and population size estimates have been based
on the expert opinion of country agency specialists. Extent or
population figures have generally been rounded to the nearest 10,
100 or 1000 units, except in the case of some very localised
habitats or small, well-studied populations.
For each feature, an indication of the reliability of habitat
extent or population size data within the UK and within each
country is given, as follows:
In some cases only a range can be quoted for habitat extent or
population size, based on expert opinion of the likely minimum and
maximum figures. The true figure could lie anywhere within this
range. In other cases, the habitat extent or population size cannot
be estimated with any degree of confidence, and it has only been
possible to indicate presence/absence.
This provisional document is based upon the most readily
available data sources. The JNCC intends to update the report as
new information becomes available. We would welcome information
about further data sources and comments upon specific habitats and
species. Those wishing to make comments should do so in writing
to: