Important Plant Areas in the UK: technical report
Introduction
The UK signed up to the Convention on Biological Diversity’s Global Strategy for
Plant Conservation in April 2002, which commits signatories to implement 16
outcome-oriented targets by 2010. Target 5 of the Strategy seeks to assure the
protection of 50 per cent of the most important areas for plant diversity. The starting
point for such an assessment is the identification of Important Plant Areas (IPAs) for
the UK, as outlined in Plant Diversity Challenge – the UK’s response to the Global
Strategy.
An Important Plant Area can be defined as a site exhibiting exceptional botanical
richness and/or supporting an outstanding assemblage of rare, threatened and/or
endemic plant species and/or vegetation of high botanic value.
To qualify as an IPA, a site needs to satisfy one or more of the following site selection
criteria:
• Criterion A – the site holds significant populations of one or more species that are
of global or European conservation concern
• Criterion B – the site has an exceptionally rich flora in a European context in
relation to its biogeographic zone
• Criterion C – the site is an outstanding example of a habitat type of global or
European plant conservation and botanical importance
IPAs are not a designation but rather aim to complement existing designations and
provide a means to plan and facilitate plant conservation at the site and landscape
scale, for example though the targeting of wider countryside measures such as agrienvironment schemes. IPAs are intended to support, inform and underpin existing
protected areas in the UK such as Areas/Sites of Special Scientific Interest and
Special Areas of Conservation.
This document summarises the steps that have been taken to select Important Plant
Areas in the UK.
The identification process
A workshop, attended by UK IPA partners, was held in October 2003 to discuss the
application of site selection criteria and guidelines for assessing site boundaries.
Several important decisions were taken at this workshop and a clear way forward
identified to work towards the completion of a UK IPA inventory by 2007. A second
workshop in May 2007 aims to finalise discussions on the UK IPA inventory and
discuss next steps with UK IPA partners.
General principles
• IPAs should be as relevant and useful to UK plant conservation as possible
• Selection methods must be consistent, rigorous and transparent
• Flexibility is needed in the application of criteria for different taxonomic groups
• The broad European site selection criteria were adhered to as far as possible
(Anderson, 2002)
• The IPA list is based on best available data and expert knowledge and opinion.
New sites can be added should more data become available or threat lists are
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revised, but all sites selected should be of sufficient quality in the first place to
remain selected in the light of new information.
When there is uncertainty surrounding the qualification of a site, which can not be
currently resolved through consultation, the site should be ‘parked’ until further
information is available.
The number, size and range of IPAs is not predetermined
The UK is relatively rich in botanical information, in having agreed Red Lists for
vascular plants (Cheffings & Farrell, 2005), bryophytes (new assessment to be
published 2007), marine algae (in draft), desmids (in draft) and charophytes (new
assessment to be published 2007) - although these tend to cover Britain rather than the
UK. Distribution atlases for vascular plants, bryophytes and several lichen genera,
and site databases for vascular plants and bryophytes are also available. However, the
‘completeness’ of databases varies across the taxonomic groups and so the site
selection process, in particular the application of criteria, needed to be flexible enough
to utilise the data available for the different taxonomic groups.
Criterion A
• There are four categories of criterion A:
o A (i) globally threatened plants
o A (ii) European threatened plants
o A (iii) Other threatened endemics
o A (iv) Other threatened near endemics
• Only credible, published threat lists or those with wide support from within expert
groups should be used to select criterion A species.
• Species can be ‘parked’ or put on a ‘waiting list’ in cases where they are of
uncertain status, taxonomically ‘dubious’, possibly under-recorded or with
insufficient site data to be able to select sites. Sites specifically for these species
can be added if and when such issues are resolved.
• Near endemic/limited range species which qualified under Aiv are interpreted in
the UK as those that are threatened according to the latest IUCN threat categories
(Cr, E and Vu) and either:
o occur in no more than 3 countries, with 50% of their range in one
country or
o are restricted to the Atlantic Biogeographic Region in Europe
In the UK, vascular plant species qualify under Criterion A through the following
recognised lists:
• Ai – IUCN Global Red List (Walter & Gillett, 1998) (e.g. Coincya wrightii)
• Aii – Annex II of the EU Habitats Directive (e.g. Saxifraga hirculus)
• Aiii (endemic) & Aiv (near endemic) – Vascular plant Red List for Great Britain
(2005) (e.g. Cerastium nigrescens - Aiii)
The UK has a number of threatened, endemic microspecies (apomicts). Instead of
attempting to identify IPAs for individual microspecies it is considered more
appropriate to identify key areas of evolution (‘process hotspots’). This approach has
been applied to the Euphrasia by the Royal Botanic Gardens in Edinburgh. Similarly,
hotspots of species and microspecies have been identified for Sorbus. Other critical
groups (e.g. Hieracia) can be included in the IPA network once further research and
data collation has been undertaken.
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In the UK, bryophyte species qualify under Criterion A through the following
recognised lists:
• Ai – IUCN World Red List of Bryophytes (2000) (e.g. Jamsoniella undulifolia)
• Aii – Annex II of EU Habitats Directive (e.g. Petalophyllum ralfsii) and
• Aii – European Red List of Bryophytes (1995) (e.g. Pallavicinia lyellii) – updates
available on the European Committee for the Conservation of Bryophytes website
• Aiii & Aiv – Bryophyte Red List (British Bryological Society, 2005) e.g.
Cephaloziella nicholsonii (Aiii) & Radula carringtonii (Aiv)
• Criterion A thresholds are based on either:
o All sites that contain five per cent or more of the national population
o The five (-ten) ‘best’ sites. This second approach, to identify the ‘best’
sites, is considered more appropriate for the UK rather than attempting
to select sites on the basis solely of population data, which is not
available for several Criterion A species. Selection of the ‘best’ sites
should be based upon a combination of population size and condition,
isolation, geographical coverage and collaboration with experts.
For lichens, the absence of a global red list for lichens meant that criterion Ai could
not be used. In consultation with UK lichenologists it was decided to use criterion Aii
to select IPA qualifying features for only two lichens (Collema dichotomum and
Catapyrenium psoromoides) from the European Red list of 1989 on the basis of a lack
of consensus on the other species listed. There was similar uncertainty over the
completion of a British Red List and the availability of comprehensive site data to
enable site selection under criteria Aiii and Aiv.
The following summarises the process for applying thresholds for criterion A:
• Initially sites for all Annex II plant species that are a primary reason for which a
SAC is designated in the UK (graded as A ‘outstanding in a European context’
and B ‘excellent examples of the feature’) were selected.
• For well-recorded species for which there are five or less sites, all sites were
selected as IPAs if they are extant sites considered worthy of inclusion.
• For well-recorded species for which there are more than five sites, expert opinion
was used to identify the ‘best’ sites.
• For species where there is insufficient information available on which to apply
thresholds - for example where there is little or no site information, the species is
thought to be severely under-recorded or there is no information on population
size and/or quality - only sites which would be thought to qualify by experts if the
species dataset was complete were selected.
Criterion B
• Criterion B is defined as a site that contains a high number of species within a
range of defined habitats. The unit of comparison for assessing species richness is
EUNIS level 2 Habitat Level. The reason for comparing species richness at this
level is to ensure that species poor habitats are not compared with species rich
habitats.
• Different approaches to the application of Criterion B were followed for different
taxonomic groups, depending on the availability of site-based data.
• Thresholds can be applied by selecting:
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o The five (-ten) ‘best’ sites for each EUNIS level II habitat or
o Up to ten per cent of the national resource (area) of each EUNIS level
II habitat
• The second approach was considered to be more appropriate since it is not
possible to select only ten sites per EUNIS level II habitat across the different
taxonomic groups considered in the UK IPA process. Especially as certain
EUNIS level II habitats such as broadleaved woodlands are particularly important
and well represented in the UK in a biogeographical context.
To identify hotspots of species richness for each EUNIS level II habitat (criterion B) a
coincidence mapping exercise was initially carried out for the whole of the vascular
plant and bryophyte flora. It was pragmatic to use the whole flora, as opposed to just
rare and threatened species, and it was thought unlikely that the inclusion of common
and cosmopolitan species would create undue bias. The process involved:
• Assigning all species to EUNIS level II habitats
• Obtaining site information for vascular plants
• Coincidence mapping of all species that occur in each EUNIS level II habitat at an
appropriate scale (down to 1 km sq)
• Identifying the richest areas for each EUNIS level II habitat
The outputs from this process were subjected to general consultation with IPA
partners.
For bryophyte sites, final decisions on IPAs for criterion B were based on expert
opinion from the British Bryological Society, and species checklists for IPAs have
been compiled.
The coincidence mapping exercise was not hugely successful for vascular plants and
a consultation was subsequently undertaken with Botanical Society of the British Isles
(BSBI) vice-county recorders to gather further data. BSBI vice-county recorders were
asked to provide lists of rare, scarce, threatened and near-threatened plants as
checklists for species-richness. These were then scrutinised for sites exhibiting
international importance for selection as IPAs. There is further work to be done in
this area and it is expected that additional vascular plant species-richness features will
be added to the UK IPA network over time.
The British Lichen Society identified important sites for lichens that qualify under
Criterion B. Several sources of information, together with expert knowledge were
being used to identify the richest lichen sites (Edwards, in press).
For charophytes, an inventory of nationally Important Stonewort Areas (ISA) was
published in 2004, and included sites of European importance (Stewart, 2004).
European ISAs qualify for inclusion in the UK IPA inventory under criterion B. Up
to five of the richest sites were selected within each of coastal dune and sand habitats
and base-rich fens, and the twelve richest sites within surface standing waters as this
habitat is so important for stonewort ecology and conservation in the UK.
The British Phycological Society coordinated the selection of IPAs for algae (Brodie
et al, in press). Initially members of the society were asked to nominate sites for both
marine and freshwater algae, and from these lists, sites that are of European
importance were selected as UK IPAs. UK IPAs for marine algae were selected using
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criterion B. UK IPAs for desmids (freshwater algae) were selected for the EUNIS
level II habitats: surface standing water (EUNIS 3: permanent oligotrophic and
dystrophic lakes, ponds and pools) and raised and blanket bog (EUNIS 3: raised bog).
The thresholds applied were: sites/areas with an exceptionally rich algal flora (over
700 desmid species) or 500 species of freshwater algae.
Sites of European importance for arable plant assemblages were identified through
the Important Arable Plant Areas project (Byfield and Wilson, 2005) and as such
qualify as UK IPAs. A weighted scoring system was used to select sites, with weight
attributed to rarity and rates of decline. The scoring system also recognised the
differing geological substrates on which arable plant communities occur and different
thresholds were set for each of ‘chalk and limestone-derived soils’, ‘clays’ and ‘sand
and freely draining acidic soils’.
Criterion C
Criterion C is split into two parts:
• Priority Threatened Habitats based on the priority habitats of Annex 1 of the
Habitats Directive and corresponding Bern Convention Habitats
• Threatened habitats based on the threatened habitats contained in Annex 1 of the
Habitats Directive and the Bern Convention not covered by (i)
Special Areas for Conservation (SACs) have been designated for all Criterion C
habitats that occur in the UK, as part of the Natura 2000 network. A list of SACs was
produced from the UK SAC database consisting of all SACs where the habitat is one
of the principal features for which the SAC has been selected (i.e. grade ‘A’ or grade
‘B’). Certain habitat features for some SACs are not necessarily of major botanical
importance, and the UK IPA partnership were not satisfied with including a long,
otherwise botanically unjustified suite of SACs in the UK IPA system. Currently sites
which could potentially qualify under Criterion C and are also SACs have only been
included on the IPA list where there is further justification through criteria A or B, or
expert opinion. This is an area of further work for the UK IPA programme.
Data
Data providers for the UK IPA project include: The Biological Records Centre,
Plantlife, Threatened Plants Database, Threatened Bryophyte Database, British
Bryological Society, Botanical Society of the British Isles Vice County Recorders,
Statutory Conservation Agencies, the JNCC UK SAC database (for Annex II species),
and additional experts.
Fungi
Plantlife, the British Mycological Society and the Association of British Fungus
Groups published a provisional assessment of the best sites for fungi in the UK in
2001 (Evans et al, 2001). Further assessment of this network of sites is required to
determine which are of European importance, at which point they can be include in
the UK IPA network. IPAs for fungal features do therefore not yet appear in the UK
IPA list.
References
• Anderson, S. (2002). Identifying Important Plant Areas. Plantlife International
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Brodie,J., John, D.M., Tittley, I., Holmes M.J. & Williamson, D.B. (in press), A
Provisional Review of Sites and Areas of Importance for Algae in the United
Kingdom.
Byfield, A.J. & Wilson, P.J. (2005). Important Arable Plant Areas: identifying
priority sites for conservation in the United Kingdom. Plantlife International,
Salisbury, UK.
Cheffings, C. and Farrell, L. (Editors), (2005), The Vascular Plant Red Data List
for Great Britain
Edwards, B.E. (in press) Selecting Important Plant Areas for Lichens. British
Lichen Society report to Plantlife.
European Committee for the Conservation of Bryophytes (1995). Red Data Book
of European Bryophytes.
Evans, S., Marren, P. & Harper, M. (2001). Important Fungus Areas: a provisional
assessment of the best sites for fungi in the United Kingdom. Plantlife
International, Salisbury, UK.
International Union of Nature Conservation (2000). World Red List of Bryophytes
Stewart, N.F. (2004). Important Stonewort Areas of the United Kingdom. Plantlife
International, Salisbury, UK.
Walter, K.S. & Gillett, H.J. (eds) (1998). 1997 IUCN Red List of Threatened
Plants. World Conservation Monitoring Centre
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