Report Cover Vol I - Clare County Library

The County Clare Wetlands Survey Patrick Crushell & Peter Foss 2008
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7 Results
7.1 CWS Data Limitations
A number of difficulties and limitations with respect to the compilation of the CWS list of wetland sites
were encountered, which the reader should be aware of, before interpretation of the data is undertaken
and to provide an estimate of the level of confidence that can be applied to the data from the current
study.
7.1.1 Wetland site identification
Although every effort was made to compile a complete map of all wetland sites in County Clare, from an
examination of aerial photographs, and from data held by external sources, it is very probable that
additional smaller wetland sites do occur which have not been mapped within the CWS GIS and database.
Therefore the list of sites presented here should not be regarded as definitive.
Primarily this lack of site identification is due to: the small nature of some wetland types making mapping
impractical (e.g. drains); it was not possible to include all areas of common habitat type such as wet
grassland, which may occur in a mosaic within other habitats including improved grassland; the
occurrence of wetland areas that cannot be identified from aerial photographs; and because detailed
habitat maps do not exist for certain areas identified as being of conservation value.
7.1.2 Wetland habitat type classification
During the selection of wetland sites, it was not always possible to ascertain with complete certainty,
which of the wetland types recognised by this survey, occurred on a given site.
In other cases, where more than one wetland type occurred within a site, in a complex mosaic of
habitats, the habitat was recorded as ‘CWS Unknown Wetland Type’. To ascertain the level 3 Fossitt
category (or even level 1 in the case of wet grassland, reed-swamp, marsh or fen) present on these sites
ground truthing via field surveys will be required.
The data-sets which contributed to the habitat map came from a variety of sources (as recorded within
GIS). This has meant that it is of varying quality, much of it originates from detailed field surveys while
other data may originate from Satellite Imagery (in the case of degraded raised bog from Corine
dataset). Therefore, it must be emphasised that the habitat map should be treated with care and used
only as an indicative map of habitat distribution.
7.1.3 Estimation of the extent of wetland habitats on sites identified
Where a detailed GIS habitat map existed, with wetland habitats mapped and characterised to Fossitt
level 3, the information was incorporated into this study, and the area data was used in final estimation
of level 3 Fossitt habitat extent within County Clare. The habitat extent data covers the entire county
(with patchy distribution) and although somewhat biased towards previously recorded sites was not
restricted to these areas.
In the case where wetland habitats could only be characterised to Fossitt level 1 or 2, the area data was
used to this level only.
As a result of these limitations the area data results provided here should be regarded as provisional.
Only with future surveys and ground truthing by experienced ecologists will level 3 habitat identification
be possible. It is envisaged that the habitat map is a ‘work in progress’ and should improve as new data
becomes available. The calculated habitat area data are a useful guide towards the relative abundance of
different habitat types in the county and we believe provide a good indication of minimum area estimates
for each habitat type.
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