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C4b. Status of UK priority species – Distribution

Type: State indicator

Indicator Description

This indicator measures change in the number of 1 km 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 the distribution of priority species for which data are available. The indicator will increase when priority species become more widespread on average, and decrease when species becomes less widespread.

This indicator should be read in conjunction with indicator C4a which provides data on those species for which abundance data are available.


  1. Summary


No additional data point since the previous publication but methodological changes have resulted in revisions to the full data series.

Official lists of priority species have been published for each UK country. There are 2,890 species on the combined list; actions to conserve them are included within the respective countries' biodiversity or environment strategies.

Between 1970 and 2016, the index of distribution of priority species in the UK decreased, with a higher proportion of species decreasing in distribution than increasing. The long-term trend is assessed as a decline of 27%.

The index was 3% lower in 2016 than in 2011, with 33% of species showing an increase and 50% showing a decline. However, this short-term decrease was not significant, and therefore the short-term assessment is stable.

Figure C4bi. Change in distribution of UK priority species, 1970 to 2016.

A line graph showing how the index of distribution of priority species in the UK has changed from 1970 to 2016. The index has fluctuated slightly from year to year but overall, by 2016 it had shown a statistically significant decrease to 77% of its base-line value in 1970.A 100% stacked bar chart showing the percentage of individual priority species in the UK that have increased (strongly or weakly), decreased (strongly or weekly) or remained unchanged in their distribution. The chart covers 2 time periods: over the long term (1970 to 2016), 16% of species showed a strong or weak increase and 37% showed a strong or weak decline; over the short term (2011 to 2016), 16% of species showed a strong or weak increase and 50% showed a strong or weak decline.


  1. The line graph shows the unsmoothed trend (dashed line) with variation around the line (shaded area) within which users can be 90% confident that the true value lies (credible interval).
  2. The figure in brackets shows the number of species included in the composite index.
  3. 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.
  4. 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).
  5. These charts are not directly comparable to previous versions of the indicator. As a result of methodological improvements and more stringent criteria in the occupancy model analysis, fewer species have been included in the 2019 iteration of this indicator compared with the 2018 iteration (714 versus 395). Also since 2018, data updates to the Biological Records Centre database for three groups (craneflies, hoverflies and leaf and seed beetles) have been received for this indicator (see method changes section for further details).

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

Latest year

Priority species – Distribution



No change (2016)

Note: Analysis of the underlying trends is undertaken by the data providers.



Download the Fiche, Datasheet and Technical background document (1 and 2) from JNCC's Resource Hub.

Download the Evidence Statement (2016). More information on the Evidence Statements, including the project report, is available on Defra's website.

Last updated: September 2019

Latest data: 2016




UK Biodiversity Indicators 2019

Published: .

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