C4. Status of threatened species

C4a. Status of priority species

 

Type: State Indicator

 

Summary

Figure C4ai.  Changes in the relative abundance of priority species in the UK, 1970 to 2010.

Figure C4ai. Changes in the relative abundance of priority species in the UK, 1970 to 2010.

Notes:

  1. Based on 210 species.  Dotted lines show the 95 per cent confidence intervals relative to the 1970 reference year.
  2. The bar chart to the right of the line graph shows the percentage of species increasing or declining over the long-term (1970 to 2010) and the short-term (2005 to 2010).
  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: Bat Conservation Trust, British Trust for Ornithology, Butterfly Conservation, Centre for Ecology & Hydrology, Defra, Joint Nature Conservation Committee, People’s Trust for Endangered Species, Rothamsted Research, Royal Society for the Protection of Birds.

 

Assessment of change in status of priority species in the UK

 

Long term

Short term

Latest year

Priority species

indicator declining
1970–2010

indicator declining
2005–2010

No change (2010)

 

  • 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 population data are available.
  • Between 1970 and 2010, populations of priority species declined to 42 per cent of the original index value, a statistically significant decrease.  Within the index over this long-term period, 30 per cent of species showed an increase, and 70 per cent showed a decline.
  • Between 2005 and 2010, populations of priority species declined by 7 per cent relative to their value in 2005, a statistically significant decrease.  Within the index over this short-term period, 41 per cent of species showed an increase, and 59 per cent showed a decline.
  • The measure is a composite indicator of 210 species from the following taxonomic groups for which there are sufficient data to create a time series: birds, butterflies, mammals, and moths.  They have not been selected as a representative sample of priority species and they cover only a limited range of taxonomic groups.  The measure is therefore not representative of species in the wider countryside.  The time series have been combined cover different time periods, were collected using different methods, and were analysed using different statistical techniques.  In some cases data have come from non-random survey samples.  See the technical background paper for more detail.

 

 

Indicator description

The indicator shows population 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.

 

Of these 2,890 species, the 210 for which robust quantitative time series of relative species abundance are available are included in the indicator.  These 210 species include birds (99), butterflies (21), mammals (11), and moths (79).  This selection is taxonomically limited at present, including no vascular or non-vascular plants, fungi, amphibians, reptiles, or fish.  The only invertebrates included are butterflies and moths.

 

The indicator declined from 100 to 42 between 1970 and 2010.  The long-term change between 1970 and 2010 is therefore assessed as a decrease.  To calculate the short-term trend, a change statistic for the 2005 to 2010 period was calculated and the data re-sampled to provide confidence intervals on that change statistic (not shown in Figure C4ai).  In 2010 the relative abundance of the 210 species included in the indicator had declined by 7 per cent relative to their 2005 levels.  The equivalent change between 2000 and 2010 was a 5 per cent decline.

 

Confidence intervals were calculated by bootstrapping, and are presented in the technical background paper.  The assessment was made on the unsmoothed time series of relative species abundance generated by the data providers.  The assessment is based on a test of statistical significance by comparing the change and 95 per cent confidence intervals between first and last date of the long- and short-term changes respectively.  The short-term change over five years between 2005 and 2010 is assessed as a decrease.  However, over a ten-year period (2000 to 2010) it would be assessed as ‘no change’.

 

The steep decline in many moth species (Figure C4aii) has an effect on the indicator as a whole.  The last moth data in the indicator is for 2007, and the final values for moth species are then held constant in the overall index until 2010.  The impact of this on the assessment has been considered: if moths are excluded from the indicator the short-term decrease between 2005 and 2010 is not significant, and the indicator would be assessed as ‘no change’.  Over ten years, from 2000 to 2010, the indicator without the moth data would be slightly positive, but not sufficiently so to be assessed as an increase.

 

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.  The short-term assessment of change is the key way of assessing progress towards halting and reversing the long-term declines of these species.    

 

 

Relevance

Priorities for species and habitat conservation are set at a country level through country biodiversity or environment strategies.  The country strategies have identified species through the four country biodiversity lists.  Species on these lists are of high conservation concern due, for example, to restricted range or population declines. 

 

Background

The time series for each species is scaled as a percentage of its value in its first year.  Each species is given equal weighting, and the annual index value is the geometric mean of the scaled species values for that year.  For species trends entering the indicator after the first year, their value in the first year is set to the geometric mean of those species trends already in the indicator.  Any missing values were estimated using linear interpolation (Collen et al. 2008), and 1 per cent of the trend average was added to any trends containing zero values (Loh et al. 2005).  Species trends ending prior to the end year of the indicator were held at their final values to the end of the data series (currently 2010). 

 

The overall trend shows the balance across all the species included in the indicator.  Populations of individual species within each measure may be increasing or decreasing in abundance (Figure C4ai).  Estimates will be revised when new data or improved methodologies are developed and will, if necessary, be applied retrospectively to earlier years.  Further details about which species are included in the indicator, and the methods used to create the priority species indicator can be found in the technical background paper.

 

Confidence intervals for each year were created using bootstrapping (Buckland 2005; Freeman et al. 2001).  In each iteration a random sample of species were selected and the geometric mean calculated.  The headline indicator (Figure C4ai) masks variation between the taxonomic groups.  Figure C4aii shows an index for each taxonomic group separately, generated using the same methods as the headline indicator.

 

Figure C4aii.  Change in relative species abundance by taxonomic group, 1970 to 2010.

Figure C4aii. Change in relative species abundance by taxonomic group, 1970 to 2010.

Notes:  Figures in brackets show the number of species included in each measure.

Source: Bat Conservation Trust, British Trust for Ornithology, Butterfly Conservation, Centre for Ecology & Hydrology, Defra, Joint Nature Conservation Committee, People’s Trust for Endangered Species, Rothamsted Research, Royal Society for the Protection of Birds.

 

Supplementary information based on general biological recording data

In addition to the time series showing changes in relative species abundance, similar time series showing changes based on general biological recording were collated.  Biological records are observations of species in a known place in space and time.  Most records are made by volunteer recorders, and whilst these data may be collected following a specific protocol, the majority of records in these datasets are opportunistic.  The intensity of recording varies in both space and time (Isaac 2012; Isaac et al. 2013), which is a challenge for estimating robust quantitative trends.  Fortunately, a range of methods now exist for producing such trends using unstructured biological records data, and these methods have been recently tested using computer simulations (Isaac 2012). The results presented in Figure C4aiii are from the ‘well-sampled sites’ model, which uses data at the level of a ‘visit’, defined as a unique combination of date and 1km2, and produces an estimated change in occurrence per year (i.e. a linear trend).  In effect the methods identify long-term changes in species distributions.

 

The times series in Figure C4aiii cover invertebrate groups missing from the analyses of abundance presented in Figure C4ai.  72 moth species contribute to both figures.  The methods described for the headline indicator were used to combine these time series into an index (Figure C4aiii).  This index shows a similar trajectory of change to the headline index (Figure C4ai), although the total decline is slightly less.  Between 1970 and 2010, 30 per cent of species showed an increase, and 70 per cent showed a decrease.  Figure C4aiii is presented as a preliminary measure which will be developed further in future years. 

 

 

Figure C4aiii.  Change in distributions of species, with 95 per cent confidence intervals, 1970 to 2010.

Figure C4aiii. Change in distributions of species, with 95 per cent confidence intervals, 1970 to 2010.

Notes:

  1. Based on 174 species.
  2. The bar chart to the right of the line graph shows the percentage of species increasing or declining over the long-term (1970 to 2010). 

Source: Bees, Wasps and Ants Recording Society; British Dragonfly Society; Centre for Ecology & Hydrology; Butterfly Conservation; Hoverfly Recording Scheme; Joint Nature Conservation Committee; Orthoptera Recording Scheme.

 

Figure C4aiv shows a composite index for each taxonomic group in Figure C4aiii separately.  These were generated using the same methods as the headline indicator.

 

Figure C4aiv.  Change in distribution of species by taxonomic group, 1970 to 2010.

Figure C4aiv. Change in distribution of species by taxonomic group, 1970 to 2010.

Notes: The figures in brackets show the number of species included in each measure.

Source: Bees, Wasps and Ants Recording Society; British Dragonfly Society; Centre for Ecology & Hydrology; Butterfly Conservation; Hoverfly Recording Scheme; Joint Nature Conservation Committee; Orthoptera Recording Scheme.

 

 

References

Buckland, S.T., Magurran, A.E., Green, R.E. & Fewster, R.M. 2005. Monitoring change in biodiversity through composite indices. Philosophical Transactions of the Royal Society of London. Series B, 360, 243–254.

Collen, B., Loh, J., Whitmee, S., McRae, L., Amin, R. & Baillie, J. 2008. Monitoring Change in Vertebrate Abundance: the Living Planet Index. Conservation Biology, 23, 317–327.

Freeman, S.N., Baillie, S.R. & Gregory, R.D. 2001. Statistical analysis of an indicator of population trends in farmland birds, BTO Research Report no. 251, Thetford.  http://www.bto.org/sites/default/files/u196/downloads/rr251.pdf

Isaac, N.J.B. 2012. Extracting trends from biological recording data. National Biodiversity Network Conference. London. doi:10.6084/m9.figshare.428369.

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.  

Loh, J., Green, R.E., Ricketts, T., Lamoreux, J., Jenkins, M., Kapos, V. & Randers, J. 2005. The Living Planet Index: using species population time series to track trends in biodiversity. Philisophical Transactions of the Royal Society, Series B, 360, 289–295.

 

 

Further development planned

The indicator of relative abundance will be refined in future as further data become available. The basis of assessment, particularly for the short-term change, may also be refined, for example, by investigating statistical smoothing to detect underlying trends and reduce the impact of particularly high or low values at the start or end of a time series.

 

Work is currently being undertaken to derive trends from distribution data (general biological recording) for more species using data collected by national recording schemes.  Time series should become available for a larger suite of taxonomic groups and therefore more species should be included in the indicator in future years, improving representativity.  In addition, analysis will be undertaken to seek to understand the impact of different priority-listing criteria in the UK’s four nations. 

 

Regardless of advances in statistical techniques there are likely to be species on the priority species lists for which little monitoring or occurrence data is available.  This is for a variety of reasons, including rarity, difficulty of detection, or those for which monitoring methods are unreliable or unavailable.  In order for the indicator to be representative of priority species, a method of assessing the changing status of these remaining data poor species will need to be considered.

 

 

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.

Aichi icon 12Target 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 primary indicator

None

 

Web links for further information

Reference

Title

Website

Bat Conservation Trust 

The National Bat Monitoring Programme

http://www.bats.org.uk/pages/nbmp.html

Bees, Wasps and Ants Recording Society

Identification guides to download

http://www.bwars.com/index.php?q=content/
identification-guides-download

British Dragonfly Society

Recording Dragonflies and Damselflies in the British Isles

http://www.british-dragonflies.org.uk/content/
recording-dragonflies-and-damselflies-british-isles

British Trust for Ornithology

Indicators of wild bird populations

http://www.bto.org/science/monitoring/developing-bird-indicators

Butterfly Conservation

Butterflies and Moths

http://butterfly-conservation.org/44/butterflies-and-moths.html

Defra Statistics

Populations of butterflies: 1976–2007 

http://archive.defra.gov.uk/evidence/statistics/
environment/wildlife/kf/wdkf10.htm

UK Butterfly Monitoring Scheme

Butterflies as indicators

http://www.ukbms.org/indicators.aspx

Centre for Ecology & Hydrology – Biological Records Centre

Recording Schemes

http://www.brc.ac.uk/recording_schemes.asp

Hoverfly Recording Scheme

Home page

http://www.hoverfly.org.uk/portal.php

Joint Nature Conservation Committee   

Seabird Monitoring Programme

http://jncc.defra.gov.uk/page-1550

Orthoptera Recording Scheme

Home page

http://www.orthoptera.org.uk/

People’s Trust for Endangered Species

National Dormouse Monitoring Programme

http://www.ptes.org/?page=186

UK Biodiversity Partnership

UK Biodiversity Action Plans 

http://jncc.defra.gov.uk/page-5155

Wildfowl and Wetlands Trust

National water bird estimates

http://www.wwt.org.uk/research/monitoring/

The Scottish Government

Scottish Biodiversity List

http://www.scotland.gov.uk/Topics/Environment/
Wildlife-Habitats/16118/Biodiversitylist/SBL

Wales Biodiversity Partnership

S42 List of priority species in Wales

http://www.biodiversitywales.org.uk/en-GB/
Section-42-Lists

Natural England

S41 List of priority species in England

http://www.naturalengland.org.uk/ourwork/
conservation/biodiversity/protectandmanage/
habsandspeciesimportance.aspx

Northern Ireland Environment Agency

Northern Ireland Priority Species List

http://www.habitas.org.uk/priority/intro.html

 

 

Download Datasheet

Download Technical background paper
 

Last updated: October 2013

Latest data: 2010