Extending the use of butterfly recording data in the UK Final Report Contract report (Defra contract WC0729) to Defra, Joint Nature Conservation Committee, Natural England, Scottish Natural Heritage, Countryside Council for Wales, Northern Ireland Environment Agency and Forestry Commission June 2011 Roy, D.B., Middlebrook, I., Cruickshanks, K., Freeman, S., Botham, M.S., Warren, M. & Brereton, T. Executive summary 1. Environmental changes such as habitat loss and degradation, climate warming and pollution are serious threats to the conservation of biodiversity. Surveillance and monitoring are important tools for measuring the impact of environmental pressures and quantifying the health and functioning of ecosystems. 2. Butterflies have been identified as an important component of the UK Terrestrial Biodiversity Surveillance Strategy. Butterflies are widely accepted as ecological indicators of ecosystem health and meet a number of the criteria for selecting indicator species. In particular, their high reproductive rates, short life cycles and low trophic level allow butterflies to respond rapidly to environmental change. Butterflies also have great popular appeal (something that eludes most insect groups) and are easy to observe and record. 3. This report reviews three years of work to develop the UK Butterfly Monitoring Scheme (UKBMS). This includes a separately published review of the current structure and main functions of butterfly monitoring in the UK. This review assesses the primary scheme, the UK Butterfly Monitoring Scheme and its relationship to other butterfly monitoring activity. 4. The UKBMS is operated by the Centre for Ecology & Hydrology, Butterfly Conservation and the British Trust for Ornithology and is funded by a multi- agency consortium including the Countryside Council for Wales, Defra, the Joint Nature Conservation Committee, Forestry Commission, Natural England, the Natural Environment Research Council, the Northern Ireland Environment Agency and Scottish Natural Heritage. The UKBMS relies on data supplied by thousands of volunteer recorders. 5. The UKBMS operates two principal methods of monitoring butterflies. Site- based assessments of butterfly communities are undertaken using traditional ‘Pollard Walks’ to sample high quality habitats. A complementary Wider Countryside Butterfly Survey (WCBS) was launched in 2009. The WCBS is a reduced-effort approach, sampling randomly selected 1km squares. 6. Methods for assessing trends in individual butterfly species and producing multi-species indicators have been developed from UKBMS data. Butterfly indicators have been published for England, Scotland and the UK. The feasibility of developing an indicator of butterfly populations in Wales and Northern Ireland has also been assessed. Methods for measuring trends in indicators have been developed using time-series analysis through the TrendSpotter program, allowing short- and long-term trends to be assessed. 7. Two methods for developing an indicator of the Impact of Climate Change using population monitoring data have been tested. Both methods are adapted from approaches used to analyse bird data. 8. The first method identifies species whose distributional extent is predicted to be positively or negatively affected by projected climate change. An indicator was then calculated as the ratio or difference between the mean population trend (on monitored sites) of climate positive and negative species. The ratio showed large year-to-year fluctuations, without a clear trend. 9. A second method to calculate an indicator of the Impact of Climate Change measures changes in community composition in response to climate. For each ii butterfly species, a Species Temperature Index (STI) was calculated as the mean, long-term average temperature of grid cells it occupies across Europe. A Community Temperature Index (CTI) was then calculated from UKBMS data as the average STI of species present in the community, weighted by the abundance of each species. The year-to-year temporal trend in CTI was then analysed using data from all monitoring sites. There was a significantly positive trend in CTI over time, with butterfly communities becoming more dominated by butterflies that are characteristic of warmer areas of Europe. 10. Analysis of long-term trend data from the UKBMS showed that for wider countryside species, the majority (15 of 25) showed no overall change, whilst equal numbers of species were either increasing or decreasing. In contrast, twice the number of habitat specialist species showed a decline compared to an increase (12 versus six), whilst 30% (8 of the 26) showed no overall change. 11. Of the 24 species of butterfly that are UK BAP Priority Species, 21 are Habitat Specialists. More than 70% of UKBAP Priority species were shown to be in long-term decline (15 of 21 species assessed), although less than 20% (4 of the 21) have declined over the last decade. 12. The decline in specialist species is linked to a range of factors, including habitat loss, changes in land management (including intensification and abandonment of traditional practices), climate change and habitat fragmentation. Habitat specialists tend to be low mobility species restricted to semi-natural habitats, whose isolated and fragmented habitat niches are most difficult to maintain in modern landscapes. Some species have recovered from long-term declines, in part due to conservation efforts, including the Silver-spotted Skipper, the Chalkhill Blue and regionally the High Brown Fritillary and the Heath Fritillary. Successful re-introductions have included the Large Blue and the Marsh Fritillary in Cumbria. Targeted management through agri-environment schemes is contributing to recovery on agriculturally managed land, although conservation efforts in woodland and on protected land have on the whole been less successful. 13. A proposal for the UKBMS over the next 3 years is to run annual wider countryside sampling to a stratified random design whilst continuing the multi and single species transect sampling on higher quality habitat. Analytical developments are proposed to increase efficiency (through implementing methods to analyse individual count data together with transect data). Developing an integrated online recording system is also a high priority. iii Contents Executive summary ........................................................................................................ ii 1 Introduction ........................................................................................................... 1 1.1 Background ...................................................................................................... 1 1.2 Butterflies as Indicators .................................................................................. 3 1.3 Current and potential uses of UKBMS for conservation policy and delivery.. 3 2 Methods ................................................................................................................. 4 2.1 Structure and main functions of the UK Butterfly Monitoring Scheme ......... 4 2.1.1 Site-based monitoring of annual butterfly abundance ........................... 4 2.1.2 Butterfly abundance in the wider countryside ........................................ 4 2.2 Accessing UKBMS data .................................................................................... 4 2.3 Analysis of trends ............................................................................................ 5 2.3.1 Models for site-specific annual survey data – species population index 5 2.3.2 Multi-species indicators ........................................................................... 5 2.4 Indicator development .................................................................................... 6 2.4.1 Methods for a Climate Change Indicator using population monitoring data .................................................................................................................. 7 3 Results .................................................................................................................. 10 3.1 Maintenance, support and development of the volunteer network ........... 10 3.1.1 Volunteer network development .......................................................... 10 3.1.2 Refining existing data collection and analysis methodologies .............. 12 3.2 Wider Countryside Butterfly Survey (WCBS) ................................................ 12 3.3 Trends in butterfly populations .................................................................... 12 3.3.1 UK and country level indices and trends ............................................... 12 3.3.2 Trends in published butterfly indicators ................................................ 14 3.3.3 Development of butterfly indicators for Wales and Northern Ireland . 14 3.3.4 Climate Change Indicator using population monitoring data ............... 16 3.3.5 European indicators ............................................................................... 18 3.3.6 Uses of UKBMS data in conservation & research (summary of data use). ................................................................................................................ 19 4 Conclusions .......................................................................................................... 20 4.1 State of UK Butterfly Populations ................................................................. 20 4.2 Future development of the UKBMS .............................................................