C4. Status of UK priority species
C4b. Distribution
Type: State Indicator
Indicator Description
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The indicator measures change in the number of 1km grid squares
across the UK in which priority species were recorded in any given
year – this is referred to as the ‘occupancy index’ and is
effectively equivalent to changes in distribution of the species.
The indicator will increase when a species becomes more
widespread, and will decrease when a species becomes less
widespread. This indicator should be read in conjunction with
C4a which provides data on those species for which abundance
information is available.
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Summary
Between 1970 and 2016, the index was relatively stable; with an
even balance of species increasing and
decreasing.
The indicator fell by 10% between 1970 and 1990, this was
followed by a steady increase until the early 2000s when the
composite trend remained stable up to 2016. The index value
in 2016 was 5% higher than the value in 1970, however this increase
is not statistically significant.
Priority species are defined as those on one or more of the
biodiversity lists of each UK country (Natural Environmental and
Rural Communities Act 2006 - Section 41 (England); Environment
(Wales) Act 2016 section 7, Northern Ireland Priority Species List,
Scottish Biodiversity List). The combined list contains 2,890
species in total. The priority species were highlighted as
being of conservation concern for a variety of reasons, including
rapid decline in some of their populations.
Figure C4bi. Change in distribution of UK priority
species, 1970 to 2015.
Notes:
- Based on 714 species. Graph shows the unsmoothed
composite indicator trend (dotted line) with variation around the
line (shaded) within which we can be 90% confident that the true
value lies (credible interval).
- Bar chart shows the percentage of species within the
indicator that have increased, decreased or shown no change in
distribution (measured as the proportion of occupied sites), based
on set thresholds of change.
- All species in the indicator are present on one or more
of the country priority species lists (Natural Environmental and
Rural Communities Act 2006 – Section 41 (England), Environment
(Wales) Act 2016 section 7, Northern Ireland Priority Species list,
Scottish Biodiversity List).
- As a result of methodological improvements in the
occupancy model analysis, a greater number of taxonomic groups and
species have been able to be included compared to the 2015 C4b
indicator. Therefore, this chart is not directly comparable
to previous versions of this indicator.
Source: Biological records data collated
by a range of national schemes and local data centres.
Assessment of change in distribution of priority species
in the UK
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Long term
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Short term
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Latest year
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Priority species – Distribution
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 1970–2016
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2011–2016
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Increased (2016)
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Of the 2,890 species on the combined priority species list, the
714 for which robust quantitative time-series of the proportion of
occupied sites are available are included in the
indicator. Relative change in distribution is measured by the
number of 1km grid squares across the UK in which they were
recorded – this is referred to as the ‘occupancy index’.
Occupancy of priority species was assessed as stable between
1970 and 2016. The index in 2016 was 5% higher than in 1970,
but taking into account the 90% credible interval this is not
considered a significant change. Similarly between 2011
and 2016 the indicator was stable. Uncertainty in the
species-specific annual occupancy estimates are incorporated into
the overall indicator; details of how this was done are included in
the technical report underpinning this indicator.
Download Fiche
Download Datasheet
Download Technical background
document
Download Technical
background document on Bayesian Occupancy Models
Download
Evidence statement
Last updated: August 2017
Latest data: 2016