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C4b. Status of UK priority species – Distribution
http://jncc.defra.gov.uk/page-6850
C4. Status of UK priority species
C4b. Distribution
Type: State Indicator
Summary
Figure C4bi. Change in distribution of UK priority species, 1970 to 2012.
Notes:
1. Based on 111 species. The line graph shows the unsmoothed trend (dashed line) and
smoothed trend (solid line) with variation around the unsmoothed line (shaded) within
which we can be 90% confident that the true value lies (credible interval).
2. The 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.
3. 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) and
Section 42 (Wales), Northern Ireland Priority Species list, Scottish Biodiversity List).
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
Long term
Short term
Priority species – Distribution
2007–2012
1970–2012
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Latest year
Decreased (2012)
C4b. Status of UK priority species – Distribution
http://jncc.defra.gov.uk/page-6850

Official lists of priority species have been published for each UK country, and actions to conserve
these priority species are included within the respective country strategies. The species included in
the indicator are those on one or more of these priority species lists for which distribution data are
available.

The indicator shows the average relative change in the distribution of 111 threatened species, as
measured by the number of 1km grid squares across the UK in which they were recorded – this is
referred to as the ‘occupancy index’. The indicator will increase when a species becomes more
widespread, and will decrease when a species becomes less widespread.

Between 1970 and 2012, the occupancy index declined by 35 per cent; 49 per cent of species
became less widespread, and 22 per cent became more widespread.

The indicator fell by 13 per cent between 2007 and 2012. Between 2007 and 2012, 55 per cent
became less widespread (48 per cent showed a strong decrease), and 42 per cent of species
became more widespread (40 per cent showed a strong increase).

The measure is a composite indicator of 111 species from the following taxonomic groups for which
there are sufficient data to create a time series: bees, wasps, ants, dragonflies, grasshoppers and
related insects, ground beetles, moths, bryophytes, and freshwater fish. Priority species were
selected in each country because they are scarce, declining or iconic. They are not representative
of wider species in general. In addition, the 111 species represent less than 5 per cent of the
complete list of priority species, and are not necessarily representative of them. They do, however,
include a range of taxonomic groups, thereby broadening the scope of the priority species
indicators, and will respond to the range of environmental pressures that biodiversity policy aims to
address, including land-use change, climate change, invasive species, and pollution.
Indicator description
The indicator shows occupancy changes of priority species in the UK: 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) and Section 42 (Wales), Northern Ireland Priority Species list, Scottish
Biodiversity List). The combined list contains 2,890 species in total. The priority species identified in
each of the four UK countries were highlighted as being of conservation concern for a variety of
reasons, including rapid decline in some of their populations. This indicator should be read in
conjunction with C4a which provides data on those species for which abundance information is
available.
Of these 2,890 species, the 111 for which robust quantitative time-series of the proportion of occupied
sites are available are included in the indicator. These 111 species include bees (40), wasps (15),
ants (1), dragonflies (4), bryophytes (7), freshwater fish (3), moths (33), ground beetles (1),
grasshoppers and related insects (3), and soldierflies (4). This selection is taxonomically limited at
present.
Occupancy of priority species has declined: between 1970 and 2012 the index fell by 35 per cent.
The index value in 2007 lies within the credible intervals of the index in 2012; therefore the short-term
trend is assessed as stable. Between 2007 and 2012 the indicator declined by 13 per cent. The
credible intervals of the index in 2012 overlapped the index value in 2007, therefore the short-term
trend is assessed as 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 background document
underpinning this indicator.
Relevance
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C4b. Status of UK priority species – Distribution
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Priorities for species and habitat conservation are set at a country level through country biodiversity or
environment strategies. Each country has an identified list of priority species, which are of high conservation
concern due, for example, to restricted range or population declines. The indicator therefore includes a
substantial number of species that, by definition, are becoming less widespread.
Measures of distribution are less sensitive to change than measures of abundance (as included in
indicator C4a). Nonetheless, if a species that has been declining starts to recover, its distribution will
stabilize, and may start to increase. If the proportion of species in the indicator that are stable or
increasing grows, the indicator will start to decline less steeply. If the proportion declines, it will fall
more steeply. Success in each country can therefore be judged by reference to trends in indicators
C4a and C4b, as well as other information on other priority species for which there are insufficient
data for inclusion in the indicator.
Background
The Bayesian occupancy approach enables an estimation of species occurrence even though the
data used in this indicator were collected without a standardized survey design (van Strien et al. 2013;
Isaac et al. 2014). For each species, records were extracted at the 1km grid square scale with
records on different days being treated separately, and an annual time-series of the proportion of sites
occupied was calculated. Each species-specific time-series was scaled so the first value in 1970 was
set to 100. The annual index was estimated as the arithmetic mean of the scaled species-specific
occupancy estimates. Each species was given equal weighting within the indicator, but because of
data gaps not all species contribute to every year of the data. Uncertainty in the species-specific
annual occupancy estimates is represented by the 90 per cent credible intervals. See the technical
background document for further detail on production of the indicator.
Species were grouped into one of five categories based on both their short-term (over the most recent
five years of data) and long-term (all years) mean annual change in occupancy. The threshold values
for each category were based on those of the wild bird indicator. See the technical background
document on the Bayesian indicator development for further detail on the calculation of the speciesspecific trends.
The trends of the taxonomic groups included within a multi-species indicator are often obscured by its
composite nature. Indicator lines have been generated for a number of sub groups using the same
method so that the trends for these groups can be seen more clearly.
The moths and the “other insects” group (consisting of the grasshoppers and related insects,
dragonflies, ground beetles and soldierflies – which were combined due to the small numbers of
species included), have undergone the most dramatic decline. Between 1970 and 2012 the index
values fell by 47 per cent for moths, and by 49 per cent for “other insects”.
The bryophytes have also experienced a decline in the proportion of occupied sites since 1970,
although over the course of the time series, this is much more variable and the indicator line has a
high level of uncertainty. In 2012, the final index value for bryophytes is 40 per cent of the value in
1970, indicating a decline of 60 per cent.
The bees, wasps and ants group, which contains the greatest number of species, has also
experienced an overall decline. In the final year of the index, this group has an index value of 72
which represents an overall decline of 28 per cent. However, looking at the indicator as a whole, for
the majority of years the index values are just above the baseline of 100, with the decline only being
seen in the most recent years.
Figure C4bii. Change in priority species (probability of occurrence), by taxonomic group, 1970
to 2012.
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C4b. Status of UK priority species – Distribution
http://jncc.defra.gov.uk/page-6850
Notes:
1. Graphs show the number of species included in brackets, the unsmoothed trend (solid
line) and variation around the line (shaded) within which we can be 90% confident that
the true value lies. Freshwater fish are not shown as there are only three species.
2. 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) and
Section 42 (Wales), Northern Ireland Priority Species list, Scottish Biodiversity List).
Source: Biological records data collated by a range of national schemes and local data centres.
Further development planned
Data are available for a number of additional taxonomic groups which are represented on the
combined Four Countries List. Due to time constraints these could not be added to this year’s
indicator, however there is the potential to add these groups in future years.
Whilst the Bayesian occupancy model is the preferred tool for future indicators, further research is
required to assess whether the short-term trends should be evaluated over five years, or over a
longer period. While they may show evidence of change in relation to conservation policy,
disentangling this from short-term effects of weather is a challenge. Currently, a smoothed line has
been added to the headline indicator to make the overall trend clear to observe. An assessment
based on the smoothed indicator should be investigated in future iterations of the indicator. Using a
smoothed trend should reduce the influence of short-term weather variation on the indicator.
Further work to investigate how to model the trends for species that failed the data requirements of
the Bayesian occupancy model may help to evaluate changes in more priority species. Initial work
using the Frescalo technique (Hill 2012) seems promising.
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C4b. Status of UK priority species – Distribution
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As the sample size increases it may become possible to investigate other ways to break down the
indicator; possibilities include, by country, upland/lowland, ecosystems/habitats, traits/life history
strategies and or by trophic level.
Goals and targets
Aichi Targets for which this is a primary indicator
Strategic Goal C. To improve the status of biodiversity by safeguarding ecosystems, species and
genetic diversity.
Target 12: By 2020, the extinction of known threatened species has been prevented and
their conservation status, particularly of those most in decline, has been improved and sustained.
Aichi Targets for which this is a relevant indicator
Strategic Goal B. Reduce the direct pressures on biodiversity and promote sustainable use.
Target 5: By 2020, the rate of loss of all natural habitats, including forests, is at least
halved and where feasible brought close to zero, and degradation and fragmentation is significantly
reduced.
Strategic Goal C. To improve the status of biodiversity by safeguarding ecosystems, species and
genetic diversity.
Target 11: By 2020, at least 17 per cent of terrestrial and inland water, and 10 per cent of
coastal and marine areas, especially areas of particular importance for biodiversity and ecosystem
services, are conserved through effectively and equitably managed, ecologically representative and
well connected systems of protected areas and other effective area-based conservation measures,
and integrated into the wider landscape and seascapes.
Web links for further information
Reference
British
Arachnological
Society –
Spider and
Harvestman
Recording
Scheme
Bees, Wasps &
Ants Recording
Society
British
Bryological
Title
Website
Home page
http://srs.britishspiders.org.uk/
Identification
guides to
download
Home page
http://www.bwars.com/index.php?q=content/identificationguides-download
http://www.britishbryologicalsociety.org.uk/
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C4b. Status of UK priority species – Distribution
http://jncc.defra.gov.uk/page-6850
Reference
Title
Society
British
Dragonfly
Society
Website
Recording
Dragonflies and
Damselflies in
the British Isles
British Myriapod Centipede and
and Isopod
Millipede
Group
recording
schemes
Butterfly
Butterflies and
Conservation
moths
Centre for
Recording
Ecology &
Schemes
Hydrology –
Biological
Records Centre
Diperists Forum Cranefly and
Empididae &
Dolichopodidae
Recording
Schemes
Ground Beetle Home page
Recording
Scheme
Hoverfly
Home page
Recording
Scheme
National Moth Home page
Recording
Scheme
Orthoptera
Home page
Recording
Scheme
Riverfly
Home page
Recording
Schemes:
Trichoptera
Soldierflies and Home page
Allies
Recording
Scheme
UK Biodiversity UK Biodiversity
Partnership
Action Plans
The Scottish
Scottish
Government
Biodiversity List
http://www.british-dragonflies.org.uk/content/recordingdragonflies-and-damselflies-britain
Wales
Biodiversity
Partnership
Natural England
S42 List of
priority species
in Wales
S41 List of
priority species
in England
http://www.biodiversitywales.org.uk/Section-42-Lists
Northern
Northern Ireland http://www.habitas.org.uk/priority/intro.html
http://www.bmig.org.uk/
http://butterfly-conservation.org/44/
butterflies-and-moths.html
http://www.brc.ac.uk/
http://www.brc.ac.uk/recording-schemes
http://www.dipteristsforum.org.uk/
http://www.coleoptera.org.uk/carabidae/recording
http://www.hoverfly.org.uk/portal.php
http://www.mothscount.org/text/27/
national_moth_recording_scheme.html
http://www.orthoptera.org.uk/
http://www.riverflies.org/trichoptera-caddisflies
http://www.brc.ac.uk/soldierflies-and-allies/home
http://jncc.defra.gov.uk/page-5155
http://www.scotland.gov.uk/Topics/Environment/
Wildlife-Habitats/16118/Biodiversitylist/SBL
http://webarchive.nationalarchives.gov.uk/
20140605090108/http:/www.naturalengland.
org.uk/ourwork/conservation/biodiversity/
protectandmanage/habsandspeciesimportance.aspx
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C4b. Status of UK priority species – Distribution
http://jncc.defra.gov.uk/page-6850
Reference
Ireland
Environment
Agency
Title
Website
Priority Species
List
References
Hill, M.0. (2012) Local frequency as a key to interpreting species occurrence data when recording effort is not
known. Methods in Ecology and Evolution, 3(1), 195–205.
Isaac, N.J.B., August, T.A., Harrower, C. & Roy, D.B. (2013) Trends in the Distribution of UK native species
1970-2010. Preliminary report to JNCC. JNCC Report No 488. http://jncc.defra.gov.uk/pdf/488_Web.pdf (PDF,
205kb).
Isaac, N.J.B., van Strien, A.J., August, T.A., de Zeeuw, M.P. & Roy, D.B. (2014a) Statistics for citizen science:
extracting signals of change from noisy ecological data. Methods in Ecology and Evolution. doi:10.1111/2041210X.12254
Isaac, N.J.B., van Strien, A.J., August, T.A., de Zeeuw, M.P. & Roy, D.B. (2014b) Extracting robust trends in
species’ distributions from unstructured opportunistic data: a comparison of methods. BioRXiv.
doi:10.1101/006999.
Van Strien, A.J., van Swaay, C.A.M. & Termaat, T. (2013) Opportunistic citizen science data of animal species
produce reliable estimates of distribution trends if analysed with occupancy models. Journal of Applied
Ecology, 50(6), 1450–1458. doi:10.1111/1365-2664.12158
Download Datasheet
Download Technical background document
Download Technical background document on Bayesian Occupancy Models
Last updated: December 2015
Latest data: 2012
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