D1. Biodiversity and ecosystem services

D1c. Status of pollinating insects

 

Type: State / Benefit indicator

 

Indicator Description

The indicator illustrates changes in pollinator distribution (bees and hoverflies) in the UK.  The indicator is based on 389 species (147 species of bee and 242 species of hoverfly) of pollinator, and measures change in the number of 1km grid squares across the UK in which they were recorded in any given year – this is referred to as the ‘occupancy index’.  Many insect species are involved in pollination but bees and hoverflies are known to be important and are presented here as an indicator of overall pollinator trend. 

Summary

 

There was an overall decrease in the pollinators indicator from 1987 onwards.  In 2014, the indicator had declined by 13% compared to the value in 1980.  The long-term trend was assessed as a decline.

Between 2009 and 2014 the indicator fell further before recovering slightly, declining by 1% overall, and is assessed as stable.

Between 1980 and 2014, 16% of pollinator species became more widespread (8% showed a strong increase), and 32% became less widespread (10% showed a strong decrease).  The ratio between increasing and decreasing species was more balanced between 2009 and 2014, with 34% of species increasing and 41% of species decreasing.

Figure D1ci.  Change in the distribution of UK pollinators, 1980 to 2014.

Figure D1ci. Change in the distribution of UK pollinators, 1980 to 2014.

Notes:

  1. Based on a total of 389 pollinators, comprising 147 wild bee species and 242 hoverfly species.
  2. Graph shows the unsmoothed composite indicator trend with variation around the line (shaded) within which we can be 90% confident that the true value lies (credible interval).
  3. Bar chart shows the percentage of species within the indicator that have increased, decreased or shown no change in occupancy, based on set thresholds of change.

Source:  Bees, Wasps & Ants Recording Society; Hoverfly Recording Scheme; Biological Records Centre (supported by Centre for Ecology & Hydrology and Joint Nature Conservation Committee).

 

Assessment of change in the distribution of pollinators in the UK

 

Long term

Short term

Latest year

Distribution of UK pollinators

indicator declining
1980–2014

2010 indicator stable2009–2014

Increased (2014)

 

As individual pollinator species become more or less widespread, the communities in any given area become more or less diverse, and this may have implications for pollination as more diverse communities are, in broad terms, more effective in pollinating a wide range of crops and wild flowers.  Despite the inter-annual variation, the overall trend for pollinators remains downward.  This indicator is not directly comparable with the previous publication as the Bayesian modelling methods have been improved, which has allowed a further 176 species (42 wild bees and 134 hoverfly species) to be included, thereby increasing the taxonomic scope of the indicator.

The indicator occupancy index was also produced for the bee (Figure D1cii) and hoverfly (Figure D1ciii) species separately.  The bee index was relatively stable up to 2007, before undergoing a sharp decline until 2010 when it stabilized.  In 2014, the bee index had declined to 81 per cent of the value in 1980.  A larger proportion of bee species had decreased than increased over both the long- and short-term, from 1980 to 2014 39% decreased and 20% increased.  From 2009 to 2014 49% decreased and 29% increased. 

Figure D1cii.  Change in the distribution of wild bee species in the UK, 1980 to 2014.

 

Figure D1cii. Change in the distribution of wild bee species in the UK, 1980 to 2014.

 

Notes:

  1. Based on 147 wild bee species.
  2. Graph shows the unsmoothed composite indicator trend with variation around the line (shaded) within which we can be 90% confident that the true value lies (credible interval).
  3. Bar chart shows the percentage of species within the indicator that have increased, decreased or shown no change in occupancy, based on set thresholds of change.

Source:  Bees, Wasps & Ants Recording Society; Hoverfly Recording Scheme; Biological Records Centre (supported by Centre for Ecology & Hydrology and Joint Nature Conservation Committee).

There was a noticeable decline in bees from 2007-2010.  Loss of foraging habitat is understood to be a major driver of change in bee distribution (Vanbergen et al, 2014).  Pesticide use has been shown to have an effect on bee behaviour and survival (Stanley et al., 2015).  However, weather effects, particularly wet periods in the spring and summer are likely to have had an impact too.  Further research would help to better understand the relative importance of these potential drivers of change.    

In contrast to the bees, the hoverfly index (Figure D1ciii) shows a gradual decline between 1987 and 2001.  In 2001, the composite index was approximately 85% of the value in 1980.  Between 2001 and 2014, the hoverfly index has remained stable, with a slight increase in the final two years.  In 2014 the index was at 90% of the value in 1980.  A greater proportion of hoverflies have declined in occupancy over the long-term than have increased (28% and 14% respectively).  However, the balance of increasing and decreasing species was more even in the short-term, with 36% and 38% of species decreasing and increasing respectively, and with an overall increase over the last three years.  It is not clear why hoverflies show a different trend to bees, although difference in the life cycle will mean they respond differently to weather events and habitat change.

Figure D1ciii.  Change in the distribution of hoverfly species in the UK, 1980 to 2014.

 

Figure D1ciii. Change in the distribution of hoverfly species in the UK, 1980 to 2014.

 

Notes:

  1. Based on 242 hoverfly species.
  2. Graph shows the unsmoothed composite indicator trend with variation around the line (shaded) within which we can be 90% confident that the true value lies (credible interval).
  3. Bar chart shows the percentage of species within the indicator that have increased, decreased or shown no change in occupancy, based on set thresholds of change.

Source:  Bees, Wasps & Ants Recording Society; Hoverfly Recording Scheme; Biological Records Centre (supported by Centre for Ecology & Hydrology and Joint Nature Conservation Committee).

 

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Download Datasheet

Download Technical background document

Download Technical background document on Bayesian Occupancy Models

Download Evidence statement

 

Last updated: August 2017

Latest data: 2014