C4. Status of UK priority species

C4b. Distribution


Type: State Indicator


Indicator Description

This 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 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 C4a which provides data on those species for which abundance information is available




No new data since the previous publication, however a combined evaluation of the long-term change in the relative abundance and distribution of priority species (C4a and C4b) has been added to the background section of this update.

Official lists of priority species have been published for each UK country. There are 2890 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 was relatively stable; there was an even balance of species increasing and decreasing in distribution and the 5% long-term increase was not statistically significant.

The index was 3% higher in 2016 than in 2011, with 39% of species showing an increase and 35% showing a decline. Once again, however this short-term increase was not significant.  



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


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



  1. Based on 714 species.  The 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).
  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), Environment (Wales) Act 2016 section 7, Northern Ireland Priority Species list, Scottish Biodiversity List).
  4. 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 the 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


Long term

Short term

Latest year

Priority species – Distribution

2010 indicator stable1970–2016

2010 indicator stable2011–2016

Increased (2016)



Download Fiche

Download Datasheet 

Download Technical background document

Download Technical background document on Bayesian Occupancy Models

Download Evidence statement


Last updated: July 2018

Latest data: 2016