By Susanna Phillips, Principal Officer – Chief Scientist Directorate, Natural England
Research published recently in the Journal of Applied Ecology highlighted the positive impact that agri-environment schemes can have on butterflies. Agri-environment schemes are a key environmental policy mechanism in England, and include biodiversity conservation as a primary objective. It is important for us to understand whether these schemes are delivering the intended environmental outcomes, and whether investment in agri-environment policy is delivering value for the public.
In this latest research, Natural England worked with scientists from the UK Centre for Ecology & Hydrology (UKCEH) and British Trust for Ornithology to combine records gathered by citizen scientists with professional survey data.
Sourcing butterfly records
This research brought together data from a four-year study designed to look at agri-environment effects on butterflies across different regions in England (the Landscape-scale Species Monitoring study) along with two citizen science surveys UK Butterfly Monitoring Scheme (UKBMS) and Wider Countryside Butterfly Survey (WCBS).
The Landscape-scale Species Monitoring study was restricted to 54 survey squares across 6 regions, so a key question remained around whether results could be extrapolated to a national scale. While the citizen science methods were not designed to understand agri-environment effects, they provide good coverage across the agricultural landscapes of England. By combining these sources of evidence, we were able to account for the strengths and weaknesses within each dataset.
Developing a model
The three surveys follow similar field protocols in monitoring butterflies along transects, and after filtering the datasets to a defined survey period of May to August, our initial scoping found the data were suitable for comparison. We then developed a common framework that allowed us to analyse the three datasets together. This model included variables representing gradients of climate, landscape and habitat to take account of environmental variation that may affect butterfly populations.
These models were run to identify relationships between agri-environment uptake density and butterfly community metrics (abundance, richness and diversity). This approach allowed us to quantify agri-environment effect more precisely than using professional survey alone.
What did the model outputs show?
Our findings showed that the presence of agri-environment management in the wider surrounding landscape was positively associated with butterfly abundance and richness in all three datasets. Relationships with butterfly diversity were more variable.
The study additionally provided evidence that the presence of agri-environment management at the local-scale was positively associated with butterfly richness (shown in the chart below)
Dr Susan Jarvis, Head of Land Use at UKCEH said:
"The results provide support for the positive effects of agri-environment on butterflies in England from multiple sources of evidence, providing evidence that these schemes are providing tangible benefits for butterflies”.
How do these findings help future decision making?
Butterfly population data published in August showed on-going declines in the abundance of butterflies in England. This underlines the critical importance of effective policy intervention. The results of the study reported here indicate that agri-environment schemes can have a significant role in supporting butterfly abundance across both lowland and upland landscapes in England.
The study contributes to our evidence base, demonstrating that where agri-environment is implemented at the right density and right spatial scales, policy spend can provide tangible benefits for pollinators, and contribute to the government's strategic targets for the environment.
This is important research highlighting the role that agri-environment intervention can play in conserving butterfly populations in the future. The findings provide evidence for policy makers and have potential to help shape agri-environment design and delivery. Notably, our conclusion that butterflies respond strongly at wider landscape scales underlines the benefits of co-ordinated management over large spatial scales.
Our research demonstrates that integrating multiple sources of evidence can provide increased power to detect effects and greater consistency in estimates. The analytical methods explored here optimise the use of existing data as an efficient and cost-effective approach to addressing policy evidence needs. This highlights the benefits partnership working and triangulating data from multiple sources, and this approach can be applied to policy evaluation across a range of sectors.
Looking ahead …
This study forms part of a wider programme evaluating the impact of agri-environment schemes. Looking ahead, Natural England is commissioning a resurvey of the Landscape-scale Species Monitoring study sites. This will test whether agri-environment intervention impacts populations of butterflies and other pollinating insects, birds and bats over time.
We’re grateful to all the landowners who granted access for these surveys, and the professional and volunteer surveyors who collected the field data used in this study.
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