Fen Management Handbook - Scottish Natural Heritage

Other than for rare or exceptional individual species, survey for particular species are generally less
important than survey for overall interest and assemblages. Target species for detailed examination
are likely to be determined by past records from a particular site, by identification of a habitat which
appears particularly suitable for a rare species, and/or on the basis of the known fauna of nearby
sites.
Less frequent but more detailed survey is more effective for invertebrates than frequent superficial
survey (though there may be exceptions if a single species is being monitored). One survey in each
management planning period, undertaken in time to feed into the next management plan, is a good
default frequency. However, limited survey funding on such occasions might well be better spent
in answering specific questions arising from the first period of management rather than in more
widespread monitoring or surveillance, provided the habitat response has been satisfactory.
1.2 Evaluation
Evaluation is the process of determining the value of the species assemblages and populations on
a site. It enables the identification and prioritisation of the features of ecological interest present on
site, and is therefore essential for setting objectives and targets for management and monitoring
programmes.
Evaluation should be considered alongside the data search and scoping survey process outlined
above, as if funds are unavailable to carry out a comprehensive site audit, it may be necessary to
allocate funds to surveys of particular species or groups based on an initial assessment of their likely
presence and value (e.g. one would normally prioritise a survey of a UKBAP priority species over a
species of less conservation concern).
There are a variety of attributes of a species that may be used as criteria for selection. These can
include legal protection status, appearance on conservation priority lists, identification as an interest
feature of the site in its designation, population conservation status, commercial value (less likely to
be appropriate for vertebrate and invertebrate species), rarity, endangerment (risk of extinction), role
as a flagship/umbrella species, importance for ecosystem function (keystone species) and value as
an indicator species. In practice, the first three of these attributes are the ones most likely to drive
prioritisation for management planning.
The main factors used to determine value are
– conservation priority (i.e. species which are rare or declining)
– abundance (presence of a significant numbers or proportion of a population, regardless of
conservation status) [e.g. 1% criteria for birds]
For ecological impact assessment, species are often assigned a value on a scale ranging from
international/national (e.g. a nationally significant population of a nationally rare species) through
to local (e.g. a population of a species significant at the local level only). An example of this type of
scale is provided in the table below, adapted from Hill et al (2005).
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