The rise and demise of the Glanville fritillary on the Isle of Wight

The Glanville fritillary is one of Britain’s rarest breeding butterflies, and is predominantly restricted to the south coast of the Isle of Wight. Populations have been monitored annually at a high proportion of known sites by counting the number of larval ‘webs’ during spring since 1996. In this paper, we present population time series for eight core sites. Populations have been observed to fluctuate considerably over the last 18 years, with a high degree of synchrony between sites. Recently, numbers of larval webs have shown a severe decline, with simultaneous extinctions occurring across many former strongholds. We combine our web count data with counts of adult butterflies from five sites of the UK Butterfly Monitoring Scheme. Together, these data suggest that the Glanville fritillary is threatened by extinction on the Isle of Wight, and that the total area used for breeding is likely no more than a few km2. The results flag up the need for a national census of remaining populations and further research to understand causes of decline, so that a conservation recovery plan can be developed

Comparison of trends in butterfly populations between monitoring schemes

Butterflies are an important indicator of the impacts of environmental change. Butterfly monitoring schemes (BMS) have provided national and Europe-wide trends in their abundance and been widely used for research. Most schemes sample sites that are self-selected by contributors and therefore tend to cover locations that are rich in butterflies. To provide a more representative assessment of butterfly populations, the wider countryside butterfly survey (WCBS) was developed with a stratified-random sample of survey sites across the UK. We compare butterfly trends from the WCBS locations against those measured from traditional butterfly transects which are typically located in areas of good quality semi-natural habitats. Across the 26 species analysed, there was a significant positive relationship between trends measured from the two schemes between 2009 and 2013, the period when both schemes were operating fully. There was a tendency (17 out of 26 species analysed) for these changes to be greater within WCBS compared to traditional BMS transects, although this effect was not consistent across comparisons between pairs of consecutive years. When assessing these individual year-to-year changes, there was however a significant correlation between the two schemes in all cases. Over relatively short time periods, weather patterns are likely to dominate butterfly population fluctuations and lead to comparable trends across monitoring schemes. Over longer time periods, differences in land management may affect habitat condition differently for protected areas versus the wider countryside and it is therefore important to maintain comprehensive butterfly monitoring programmes to detect and interpret such effects

Impacts of climate change on national biodiversity population trends

Climate change has had well-documented impacts on the distribution and phenology of species across many taxa, but impacts on species’ abundance, which relates closely to extinction risk and ecosystem function, have not been assessed across taxa. In the most comprehensive multi-taxa comparison to date, we modelled variation in national population indices of 501 mammal, bird, aphid, butterfly and moth species as a function of annual variation in weather variables, which through time allowed us to identify a component of species’ population growth that can be associated with post-1970s climate trends. We found evidence that these climate trends have significantly affected population trends of 15.8% of species, including eight with extreme (> 30% decline per decade) negative trends consistent with detrimental impacts of climate change. The modelled effect of climate change could explain 48% of the significant across-species population decline in moths and 63% of the population increase in winged aphids. The other taxa did not have significant across-species population trends or consistent climate change responses. Population declines in species of conservation concern were linked to both climatic and non-climatic factors respectively accounting for 42 and 58% of the decline. Evident differential impacts of climate change between trophic levels may signal the potential for future ecosystem disruption. Climate change has therefore already driven large-scale population changes of some species, had significant impacts on the overall abundance of some key invertebrate groups and may already have altered biological communities and ecosystems in Great Britain

Modelling Landscape-scale Species Response to Agri-Environment Schemes

Agri-environment schemes (AES) are the most significant environmental policy delivery mechanism in England, and include the conservation of biodiversity as a key objective. Provisional results from the ongoing Landscape-scale species monitoring of AES (LandSpAES) baseline field survey have shown some positive responses of mobile taxa to AES gradients at local (1km2) or landscape (3 × 3km) scales. However, it is not known whether these provisional results might be more broadly applicable outside the regions surveyed in the LandSpAES project, i.e. in other regions, or nationally. Here, we present the findings of an analytical project to explore the use of national Citizen Science (CitSci) scheme data, to investigate whether similar relationships with AES gradients would be found at a national scale in CitSci data to those shown with LandSpAES data, and whether integrated modelling was possible with combined CitSci and LandSpAES datasets. The design of LandSpAES has high power to detect AES effects, including the independent testing of the local and landscape AES gradients, but is restricted to six regions. The national CitSci are more representative of England as a whole, but have not been designed to detect AES effects. The aim of this project was to determine whether the provisional taxon responses to the AES gradients found in the LandSpAES project could be detected at a national scale using CitSci scheme data. To achieve this aim, three key questions were addressed through the analytical work: 1) Can addition of covariates account for environmental variation between survey squares in each dataset, to improve the comparability of AES gradient effects between LandSpAES and CitSci schemes? 2) Do the CitSci scheme datasets show similar relationships between taxa responses and the AES gradients, to those found with the LandSpAES data? 3) Can integrated approaches to combining datasets be used to jointly model CitSci and LandSpAES data, and does integrated modelling reduce uncertainty in quantifying the effects of AES gradients on taxa responses at a national scale across England

Designing a survey to monitor multi-scale impacts of agri-environment schemes on mobile taxa

Agri-environment schemes (AES) are key mechanisms to deliver conservation policy, and include management to provide resources for target taxa. Mobile species may move to areas where resources are increased, without this necessarily having an effect across the wider countryside or on populations over time. Most assessments of AES efficacy have been at small spatial scales, over short timescales, and shown varying results. We developed a survey design based on orthogonal gradients of AES management at local and landscape scales, which will enable the response of several taxa to be monitored. An evidence review of management effects on butterflies, birds and pollinating insects provided data to score AES options. Predicted gradients were calculated using AES uptake, weighted by the evidence scores. Predicted AES gradients for each taxon correlated strongly, and with the average gradient across taxa, supporting the co-location of surveys across different taxa. Nine 1 × 1 km survey squares were selected in each of four regional blocks with broadly homogenous background habitat characteristics. Squares in each block covered orthogonal contrasts across the range of AES gradients at local and landscape scales. This allows the effects of AES on species at each scale, and the interaction between scales, to be tested. AES options and broad habitats were mapped in field surveys, to verify predicted gradients which were based on AES option uptake data. The verified AES gradient had a strong positive relationship with the predicted gradient. AES gradients were broadly independent of background habitat within each block, likely allowing AES effects to be distinguished from potential effects of other habitat variables. Surveys of several mobile taxa are ongoing. This design will allow mobile taxa responses to AES to be tested in the surrounding countryside, as well as on land under AES management, and potentially in terms of population change over time. The design developed here provides a novel, pseudo-experimental approach for assessing the response of mobile species to gradients of management at two spatial scales. A similar design process could be applied in other regions that require a standardized approach to monitoring the impacts of management interventions on target taxa at landscape scales, if equivalent spatial data are available