Status of Threatened Species

Status of Threatened Species

24 Oct 2013

Stone Curlew by P Doherty

The new official Biodiversity Indicator on the Status of Priority Species, shown below, shows that the abundance of priority species in the UK has declined by 58% between 1970 and 2010. There are several important points to make about this starkly negative statistic. First, the main figure is based solely on population trends in birds, butterflies, moths and mammals – familiar taxonomic groups for which the UK has rigorous, largely volunteer-based monitoring schemes in place. There are significant differences in the trends for these four groups (see breakdown by species groups below) and the main indicator includes nothing about the trends in other insects, other invertebrates, vertebrates or plants. Secondly, species are included if they are on the Priority List of one of the four countries in the UK and hence by definition largely represent threatened species which are declining, rare or vulnerable.  In this sense, the overall decline is not surprising but it is important to track whether the trend shows any sign of improvement.

Change in the relative abundance of priority species in the UK, 1970 to 2010
(Click to enlarge)

The inclusion of so many bird species in this new Biodiversity Indicator is a testament to the quality of bird recording in the UK and the dedicated efforts of so many volunteer birdwatchers.  The trends for birds on the Priority Species lists are based on standardised recording schemes such as the Breeding Bird Survey, the Wetland Bird Survey, the Rare Breeding Bird Panel, the seabird monitoring programme and periodic surveys of scarcer species. The fluctuating but ultimately stable line for birds compared to moths and butterflies reflects the fact that this trend includes the population recoveries of some of our rarest birds such as Bittern, Stone Curlew and Red Kite, much of this due to effective conservation measures. This line includes the steep declines of species of conservation concern such as Spotted Flycatcher and Corn Bunting, but also trends in numbers of wintering waterbirds which are on the Priority Lists because of concern about their wintering populations (eg. Bewick’s Swan and Red Knot). The inclusion of this diverse array of population trends  from all landscape types explains why the birds in this indicator is relatively stable compared to the declines in more specialist farmland and woodland birds reported in the recent update of the wild bird indicators. There are fewer species of mammals on Priority Lists, and many of the most familiar species are recently arrived non-natives. The mammal trends here are mainly for bat species, also Common Dormouse and Brown and Mountain Hare, trends for both hare species based on counts by volunteers during BBS visits.

Change in relative species abundance by taxonomic group, 1970 to 2010.
(Click to enlarge)

Another important point is that this indicator is the result of close collaboration between scientists from a wide range of NGOs, research organisations, specialist recording schemes and the Government, to combine trends from different taxa for a more representative indicator of the status of threatened species. An early version of the indicator was first published as the Watchlist Indicator in State of Nature. Although the main statistic includes information from a small group of well-monitored taxa, additional work has been carried out by the consortium to generate trends in the frequency of occurrence from a wider group of taxa, based on novel analyses of a suite of special recording schemes of dragonflies, bees, wasps, ants, hoverflies, moths and grasshoppers.  The trends in this group – all insects – are also strongly negative, and have been presented as supplementary information for this indicator. Work is planned over the next year to fully assess these results and carry out similar analyses on other taxa.

Change in distribution of species by taxonomic group, 1970 to 2010.
(Click to enlarge)

Further information on the new Priority Species Indicator can be found in the downloadable Technical Report, from David Noble at BTO, or any of the other collaborating organisations.


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