Introduction to the guidance manual
10. Attributes for species interest features
 
 
 
 
Assessing favourable condition for species interest features could be by direct means (e.g. measures of species population size) or via indirect means (e.g. extent/condition of suitable habitat). These are complementary, and a balance (section 10.3) should be struck for any particular feature having due regard to both needs and practicalities.
 
10.1 Indirect measures
The use of direct measures is expected to be the norm, but for many species (especially cryptic and/or poorly known species, such as many invertebrates) it is very difficult to make reliable estimates of population size; in some cases (e.g. wood-boring beetles), population assessment may even destroy the species' habitat. Even where quantitative assessments can be made (e.g. birds), populations may fluctuate widely on a seasonal, annual or longer-term basis; defining appropriate target/limit values may be problematic if the population dynamics of the species are unknown. Given that management for notable species is normally undertaken by managing the habitat, rather than directly managing the species, it is normally appropriate to include habitat attributes within conservation objectives for species interest features where the habitat needs of the species are known.
 
10.2 Direct measures
Notwithstanding the foregoing remarks, some direct measure of a species feature is clearly highly desirable, as over-reliance on habitat attributes could lead to misleading conclusions. The relationships between habitat condition/extent and associated species are often poorly-known. If condition assessment for species relied solely on habitat attributes it would be possible for the habitat to be in apparently favourable condition, but for the associated species to have declined to the point of extinction. Species may also be influenced by factors other than habitat condition/extent, e.g. disturbance, as in relation to bat roosts.
 
10.3 A balance of approaches
The solution is to use a combination of approaches, tailored to the particular interest feature. The following principles are advocated:
 
  • In general, attributes for species interest features should include both assessments of habitat extent/quality and assessments of the species population where data exist through recording schemes, or can be easily and reliably obtained without significant costs or delays.
  • Quantitative assessments of population size should only be used when:
    1. the species population can be counted or measured reliably, e.g. most birds, some vascular plants, some invertebrates (butterflies and dragonflies); and
    2. meaningful targets/limits can be set which take population fluctuations into account; and
    3. assessment methods avoid significant additional costs, time, or generating a need for higher competencies of local staff.
  • Where quantitative assessments cannot be used, conservation objectives should generally incorporate species presence/absence, i.e. for a species feature to be in favourable condition the species should usually be recorded at least once during a 6-year reporting cycle.
  • Some habitat attributes should be used, provided the habitat requirements of the species are broadly known – if necessary, further work should be undertaken to establish this.

 

There will be a gradient in the balance of attributes from groups where the habitat attributes will predominate and where presence/absence of the species may be the most that can be expected to be monitored, through to groups where species population data will predominate and where only major changes of habitat may be worth recording. Most species interest features are likely to lie between these two extreme positions and, for these, population data and habitat attributes will both be important. When assembling evidence of feature condition, the use of relevant 'contextual' information on species populations, collected through existing recording schemes or specially commissioned surveillance schemes outwith CSM methods should always be considered.
 
For certain species, disturbance or predation are major factors affecting populations, and conservation objectives should include attributes relating to minimising these factors. There is obviously a cross-over here to the management plan for the site.