Important Plant Areas for algae - Natural History Museum

5.41 Criterion A – threatened species
As mentioned above, IUCN criteria have been adopted when assessing potential UK Red Data List
desmids (see Appendix 8.1). One of the criteria used for selecting an important site/site complex (area) is
the number of potential UK Red Data List desmid species present.
We defined the ‘best’ UK desmid sites as those containing ‘at least 5 desmids belonging to the potential
Red Data List falling into the IUCN categories of critically endangered (Category 1) and endangered
(Category 2)’.
The extinct category has not been used although a significant number of desmid taxa have not been
recorded for at least 50 years. Very probably these desmids are very rare and might simply have been
‘missed’ by DW. Any desmid not recorded over the past 50 years is regarded here as ‘Data Deficient’
rather than extinct. Some of these ‘missing’ desmids are endemics with the majority known only from
endangered or vulnerable habitat types mentioned in the EUNIS list.
5.42 Criterion B1 – species-richness
UK and European IPAs: UK IPAs for desmids are defined here as ‘those in vulnerable or threatened
habitats containing at least 40 desmid species. Some sites/areas with lower diversities are only included
if containing at least 5 potential UK Red List species’; European IPAs for desmids are defined as ‘those
in vulnerable or threatened habitats containing at least 70 desmid species’.
5.43 Criterion B2 - long history of study
The provisional assessment of the best UK fungi sites (Evans et al., 2001) uses criteria in addition to
those recommended by Anderson (2002). The potential fungal sites include those having long lists of
species, assemblages of rare and indicative species, new records of UK species, a long history of
recording and sites ‘outstanding’ for fungi.
The criterion of ‘long history of study’ is used for considering important sites/areas for freshwater algae
in the UK. It can be applied to permanent standing bodies of water for which records sometimes go back
over several decades (e.g., Windermere, Priest Pot, Lough Neagh, Loch Leven). Sometimes these sites
may be representative of a particular habitat type (e.g., nutrient-enriched lakes). All these sites or areas
are also considered ‘data deficient’ since uncertainty surrounds their current status.
5.44 Criterion C - priority threatened habitats
According to Anderson (2002), the criteria for selecting IPAs allow for ‘the five ‘best’ sites, of priority
threatened habitat of major significance on Annex 1 of the EU Habitats Directive’, or ‘up to 5 ‘best’ sites
of other threatened (but non-priority) habitats listed on the annex’. Threatened and priority threatened
habitats mentioned in Annex 1 that are of special significance to desmids are listed in Table 5.3. It is not
possible to readily select the ‘best’ 5 sites since the data are too incomplete. A possible approach might be
to choose those containg at least 5 potential UK Red List species. For now all desmid sites that conform
to the criteria selected here are listed with the most species-rich ones considered of European importance.
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