Tuesday 7 April 2020
The UKBMS is a long-term monitoring scheme (running since 1976) involving repeat sampling at thousands of locations across the UK. The key method involves regularly counting butterflies along defined transects on days with specified weather criteria. The surveys are carried out by over 2,500 volunteers annually and take place across over 1,000 nature sites (not just Nature Reserves).
Adonis Blue. Photo: Ashley Cox Duke of Burgundy. Photo: Roy McDonald
Although trends for UK butterfly species vary, just under a third of butterfly species assessed in the UK showed a significant long-term decline in abundance (31%), compared to 26% showing a significant long-term increase. However, the situation is been more positive compared to the last decade, with 6 species (10%) showing a statistically significant increase over this time, while 5 species (9%) showed a significant decline. Following a modest recovery in 2018, 2019 was an excellent year for butterflies. Just over half of species (53%) showed a higher population index in 2019 compared to the year before. For species (Chequered Skipper, Orange-tip, Brimstone, and Marbled White) had their best year on record in the UK in 2019, and no species had their worst year on record in 2019. However, note that some habitat specialist species have not recovered to the higher numbers that were typical in the early 1970s, whilst some wider countryside species are in long-term decline.
The report pointed to various drivers for the long-term declines in abundance, including the extent, condition and fragmentation of habitats caused by the intensification of farming, changes in forestry practices, urban development, pollution and climate change. Weather conditions can also create noticeable fluctuations in butterfly populations from one year to the next, with warm sunny weather being preferable for butterflies during their flight period. The spring and summer of 2019 was warmer than average although the summer was also relatively wet. Various targeted conservation management projects to protect and improve habitat can also have a positive impact on species abundance.
Why are the results important?
Butterfly populations are used as indicators for environmental change due to their rapid and sensitive responses to subtle habitat or climatic changes, and to reflect the responses of other wildlife. The results of the report also demonstrate the value of a citizen science approach. Over 2,500 skilled volunteers were involved, and this approach enables wide-scale simultaneous sampling coverage and gives health benefits to the volunteers engaging in an active out-of-doors conservation/ monitoring project. The data collected from the UKBMS report are widely used in scientific research, for local site management, and have broad policy relevance. UKBMS data feed into European indicators, and UK biodiversity indicators as part of measuring progress towards EU and CBD targets. UKBMS data has informed UK reporting on the European Habitats Directive (for Marsh Fritillary and Large Blue), and has fed into country level indicators and reporting on Priority Species e.g. S41 species in England.
These records only made possible by the huge citizen science effort from 1,000s of dedicated and skilled volunteers. Chalk, Cherries and Chairs' Tracking the Impact project (funded by National Lottery Heritage Fund) is seeking to replicate this study in partnership with Butterfly Conservation across the Central Chilterns. We are targeting annual survey coverage of birds, butterflies and plants across 50 1km squares and to help train the next generation of butterfly surveyors. To date we have 15 people signed up to take on a survey square and a further 32 signed up to go on a species identification course. If you want to find out more about how you can get involved contact Nick Marriner at email@example.com