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Insects play a pivotal role in natural processes that support other living organisms, and human health and wellbeing. Roles include pollination, pest and weed regulation, decomposition, nutrient cycling, and provision of food for wildlife and humansThey can also be agricultural pests or transmit disease. Insects are key indicators for monitoring ecosystems and concerns about insect decline have arisen following studies showing large declines in insect abundance and biomass. However, the trends for global insect populations remain largely unknown, although studies in Europe have found insect abundance or biomass declined between 38% and 75%.

The UK has more data than many countries due to its long-term recording schemes, natural history collections, citizen science engagement and insect research community. Emerging labour-efficient methods can help data collection through remotely monitoring larger areas, but current data are limited by gaps in what is measured and how. The data shows the UK has experienced extinctions and declines in abundance, biomass and distribution of insects. Declines in abundance or distribution have been seen in bees and hoverfliesbutterflies and moths, beetles, and freshwater insects, but some species are increasing in biomassThere are a variety of drivers behind insect decline, such as habitat loss, chemical use and climate change, and their impacts differ across habitat, species and time.

Key points in this POSTnote include: 

  • There have been documented declines in insect species and populations. Generalist species are less likely to decline than more specialised species. The impacts of this on ecological processes are poorly quantified.  
  • The UK has unparalleled data from long-term monitoring, but it is limited by gaps in what is measured and how. There are few long-term data sets with abundance data.  
  • Drivers of decline, such as habitat loss, are common across insect groups and can interact to cause combined pressure on populations. However, environmental changes can benefit some species while negatively affecting others.  
  • Interventions, such as habitat creation, may play a role in halting declines, but the scale and types need careful consideration

Further information on these issues is available in POSTbrief 36 Understanding insect decline: data and drivers

Acknowledgements 

POSTnotes are based on literature reviews and interviews with a range of stakeholders and are externally peer reviewed. POST would like to thank interviewees and peer reviewers for kindly giving up their time during the preparation of this briefing, including:

Professor Simon Leather, Harper Adams University  

Dr James Bell, Rothamsted Insect Survey* 

Dr Chris Shortall, Rothamsted Insect Survey*  

Dan Blumgart, Rothamsted Insect Survey* 

Professor Simon Potts, University of Reading* 

Dr Tom Breeze, University of Reading* 

Dr Deepa Senapathi, University of Reading* 

Dr Claire Carvell, Centre for Ecology & Hydrology (CEH)* 

Dr Ben Woodcock, Centre for Ecology & Hydrology (CEH) * 

Professor Helen Roy, Centre for Ecology & Hydrology (CEH) * 

Dr Jamie Alison, Centre for Ecology & Hydrology (CEH) * 

Dr Nick Isaac, Centre for Ecology & Hydrology (CEH)* 

Dr David Roy, Centre for Ecology & Hydrology (CEH) 

Dr Gary Powney, Centre for Ecology & Hydrology (CEH) * 

Dr Marc Botham, Centre for Ecology & Hydrology (CEH) * 

Professor Richard Pywell, Centre for Ecology & Hydrology (CEH) * 

Dr Charlotte Outhwaite, Centre for Ecology & Hydrology (CEH), University College London*  

Dr Lynn Dicks, University of Cambridge, University of East Anglia, EKLIPSE, Conservation Evidence, IPBES* 

Professor Steve Ormerod, Cardiff University* 

Dr Christopher Hassall, University of Leeds* 

Professor Bill Kunin, University of Leeds*  

Dr Richard Gill, Imperial Collage London*  

Professor Jane Memmott, University of Bristol  

Dr Kath Baldock, University of Bristol, Northumbria University  

Professor Chris Thomas, University of York*  

Professor Jane Hill, University of York  

Professor Mark Brown, Royal Holloway University of London* 

Professor Dave Goulson, University of Sussex*  

Sir Charles Godfray, University of Oxford  

Professor Jeff Ollerton, University of Northampton 

Professor Alfried Vogler, Imperial College London  

Seirian Sumner, University College London  

Don Monteith, Environmental Change Network  

Dr Deborah J Steele, Department for Environment, Food and Rural Affairs (Defra), UK*  

James Philips, Natural England*  

Jon Curson, Natural England* 

Andy Brown, Natural England* 

Jon Webb, Natural England* 

Matt Shardlow, Buglife*  

Chris Hartfield, NFU*  

Richard Fox, Butterfly Conservation*  

Luke Tilley, Royal Entomological Society  

Ben Sykes, Ecological Continuity Trust  

Margaret Ginman, Bee Farmers association  

Dr Julie Ewald, Game and Wildlife Conservation Trust  

Dr John Holland, Game and Wildlife Conservation Trust 

*Denotes people who also acted as external reviewers of the briefing


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