Thousands of volunteers have helped play a key role in new research which shows butterflies are declining more quickly in urban areas than in the countryside.
Data, contributed by thousands of volunteers as part of the UK Butterfly Monitoring Scheme (UKBMS), helped compare trends for 28 species in urban and rural areas with dramatic declines identified for the Small Copper and Small Heath butterflies.
The UKBMS is run by the Centre for Ecology & Hydrology (CEH), Butterfly Conservation (BC) and the British Trust for Ornithology, in partnership with the Joint Nature Conservation Committee. It is an example of a long-established citizen science monitoring scheme.
The study, a collaboration between experts at Butterfly Conservation, the University of Kent and CEH, found that over a 20-year period urban butterfly abundance fell by 69 percent compared to a 45 percent decline for butterflies in rural areas.
The Small Copper and Small Heath declined much more dramatically in towns and cities than in the countryside.
Between 1995 and 2014, the number of Small Copper butterflies fell by 75 percent in urban areas compared to a 23 percent decline in the countryside. The Small Heath experienced an abundance decline of 78 percent for urban areas, compared to a smaller decline of 17 percent in rural areas.
Dr David Roy, CEH Head of Monitoring, said, "It is through the analysis of long-term records that we can show that butterfly populations are declining in urban areas.
"These high quality, world-leading, data are only available because of the continued dedication of thousands of volunteer butterfly enthusiasts contributing to the UK Butterfly Monitoring Scheme.
“This paper builds upon the rich body of research using the UKBMS."
"These high quality, world-leading, data are only available because of the continued dedication of thousands of volunteer butterfly enthusiasts contributing to the UK Butterfly Monitoring Scheme." Dr David Roy, Centre for Ecology & Hydrology
The study, published in the journal Ecological Indicators, also showed that most butterflies living in our towns and cities are emerging earlier and are on the wing for longer than the same species living in rural areas.
Lead researcher Emily Dennis, from BC and the University of Kent, said, "We used sophisticated statistical techniques to reveal that practically all butterflies we assessed were found to be struggling in urban areas, most likely due to the combined effects of habitat loss, climate changes and the intensification of land use."
Butterflies in urban areas emerged on average two days earlier than their countryside counterparts with urban Brimstones emerging five days earlier than those found in rural locations.
"All butterflies we assessed were found to be struggling in urban areas, most likely due to the combined effects of habitat loss, climate changes and the intensification of land use." Dr Emily Dennis, University of Kent
Flight periods for many of the species studied were also found to be slightly longer for urban butterflies than their rural counterparts.
Above: The Small Heath butterfly has declined much more dramatically in towns and cities than in the countryside
The likely cause behind the earlier emergence and longer flight periods of urban butterflies is what is known as the ‘urban heat island’ effect. This is where urban areas are slightly warmer than the surrounding countryside due to human activities.
Professor Tom Brereton, BC Head of Monitoring, said, "Seeing butterflies each summer is a vital part of the quality of life for millions of people in the UK.
"The study shows that in urban areas where most people live and experience the natural world butterflies are in even more trouble than in our intensively farmed countryside. We must act now to ensure that we manage the environment to maintain the very things we cherish."
Butterfly Conservation issued a press release in relation to this story.
Paper reference: Emily B Dennis et al, “Urban indicators for UK butterflies,” Ecological Indicators, doi 10.1016/j.ecolind.2017.01.009, published online and open access February 2017.
The UK Butterfly Monitoring Scheme (UKBMS) has since 1976 provided a structured survey methodology to monitor butterflies across the UK year-on-year. This long-term butterfly data enables us to assess the impacts of land use, climate change and the progress of the UK Biodiversity Action Plan, agri-environment schemes and site condition monitoring of Sites of Special Scientific Interest (SSSIs).
UKBMS is run by the Centre for Ecology & Hydrology, Butterfly Conservation and the British Trust for Ornithology, in partnership with the Joint Nature Conservation Committee and is supported and steered by the Forestry Commission, Natural England, Natural Resources Wales, Northern Ireland Environment Agency and Scottish Natural Heritage.