Alison Riggs’s scientific contributions

In recent years, scientists and the media have drawn attention to global declines in insect abundance, the consequences of which are potentially catastrophic. Invertebrates are critical to ecosystem functions and services, and without them, life on earth would collapse. However, there has been insufficient data to make robust conclusions about trends in insect abundance in the UK, because standardised insect sampling approaches are not widely applied to all insect groups or at a national scale. Here, we demonstrate the use of an innovative and scalable invertebrate sampling technique conducted by citizen scientists, to examine the difference in invertebrate abundance in the UK over a 17-year timeframe. The 'windscreen phenomenon' is a term given to the anecdotal observation that people tend to find fewer insects squashed on the windscreens of their cars now, compared to in the past. This observation has been ascribed to major declines in insect abundance. In this study, citizen scientists were asked to record the numbers of squashed insects and other invertebrates on their vehicle number plates following a journey, having first removed any residual insects sampled on previous journeys. We compared the number of insects sampled by vehicles in 2019 (n = 599 journeys in Kent) and 2021 (n = 3,348 journeys nationwide) with the results of a nationwide survey using this methodology led by the RSPB ('Big Bug Count') in 2004 (n = 14,466 journeys). The results show that the number of insects sampled on vehicle number plates in the UK decreased by 58.5% between 2004 and 2021, and that these differences were statistically significant. A comparison of the 2004 national data with the 2019 data from Kent showed a 53.7% decrease. The greatest decreases in splat rate between 2004 and 2021 occurred in England (65%) whilst journeys in Scotland recorded a comparably smaller decrease (27.9%), with intermediate decreases in Wales (55%). These results are consistent with the declining trends in insect populations widely reported by others, and informs a growing requirement for conservation research, policy and practice targeted at invertebrates in the UK. However, our results are based on data with low temporal resolution and consequently we interpret this change between two points in time with caution. Furthermore, inter-annual variation in a range of unmeasured factors, such as wind speed, predation or land-use change, could significantly influence the observed pattern. To draw robust conclusions about long-term trends in insect populations in the UK, scientists require data from multiple years, over long time periods, and over large spatial scales-the Bugs Matter citizen science survey has demonstrated that it has the potential to generate such data.

Landscape-scale conservation is the combined contribution of multiple actions, on multiple sites, and by multiple stakeholders, to the resilience of ecological networks. This results in a complex matrix of interventions and policies in space and time. Monitoring the outcomes of landscape-scale conservation therefore presents significant challenges to the individuals and organisations involved in its delivery. Monitoring of site-scale outcomes is well-established and best practice available and adopted. Landscape-scale monitoring is in its infancy by comparison. The absence of common standards and approaches reflects both the infancy of landscape-scale conservation and the scale and complexity of the challenge. The project sought to address these challenges by consulting widely with a community of conservation practitioners to gather expertise and information on their needs from landscape-scale monitoring. It reviewed and analysed existing landscape-scale monitoring approaches, generated consensus on priorities and principles, and developed partnerships to design and test sustainable monitoring approaches. This informed the development and testing of a monitoring framework and practical approaches to landscape-scale monitoring. The project developed a practical framework structured around a series of logical steps to inform the creation of monitoring objectives and programmes. This framework signposts guidance, outputs and case studies developed by the project. Guidance is offered around defining landscape parameters, key attributes of monitoring programmes, landscape monitoring themes, priority themes and questions for landscape-scale monitoring to address, defining and articulating monitoring objectives, and criteria for selecting landscape indicator species.

A growing body of recent evidence highlights population declines in insects and other invertebrates at global scales, the consequences of which are potentially catastrophic. Invertebrates are a critical component of ecosystem function, and all functional groups (herbivores, detritivores, parasitoids, predators and pollinators) are at risk. Without them life on earth would collapse. Considerable conservation effort is targeted at invertebrates. The focus of delivery of conservation action has shifted from site to landscape-scale, and practitioners seek to evidence landscape-scale outcomes of conservation action. Here we used an innovative invertebrate sampling technique conducted by citizen scientists to assess the difference in invertebrate abundance in the south-east of England over a 15 year timeframe. The windscreen phenomenon is a term given to the anecdotal observation that people tend to find fewer insects squashed on the windscreens of their cars now, compared to a decade or several decades ago. This effect has been ascribed to major global declines in insect abundance. Using a standardised sampling grid termed a ‘splatometer’, members of the public were asked to record the number of insects and other invertebrates squashed on the number plate of their car, having first cleaned the number plate before commencing a journey. A national survey using this methodology led by the RSPB took place in 2004, and by repeating the survey in Kent in 2019 we were able to compare the abundance of invertebrates between these points in time. Between 2004 (n=3838) and 2019 (n=667) there was a statistically significant difference in ‘splat density’ of the order of approximately 50%, from an average of 0.2 splats per mile to 0.1 splats per mile. This difference mirrors the patterns of decline widely reported by others. This observation is based on data from two points in time and consequently we recognise it does not constitute a trend and cannot be interpreted as a decline. Inter-annual variation in variables such as weather cannot be ruled out as factors influencing the observed pattern. More data over a number of years will be required to confirm the direction of any trend, however the observed pattern correlates with examples of decline. We addressed two limitations of the 2004 survey. Firstly, in 2004 participants were not provided guidance on journey length, and a large number of long journeys spanning several counties resulted in the data providing poor spatial resolution of variation. Only variation between regions was resolved in the 2004 data, but by encouraging participants to submit data from both short and long journeys, we were able to map spatial variation in splat density within Kent. The second limitation we addressed concerned a criticism levelled at the methodology in terms of the effect of vehicle design on the rate of invertebrate sampling. Modern cars are more aerodynamically designed than in the past, and changes over time may affect the numbers of insects getting squashed. We actively recruited classic car owners to take part in the survey, allowing us to collect data using cars ranging in age from 1957 to 2018. We found a small but statistically significant positive relationship between vehicle age and splat density, suggesting that modern cars squash more invertebrates that older cars. This suggests that the signal from the difference in insect abundance is strong enough to be apparent in spite of more efficient sampling by newer vehicles. This study has the potential to add to the growing body of evidence for significant invertebrate declines in the UK, highlighting a significant effect in Kent and the south-east of the UK, and supports the case for conservation policy and practice to reverse declines and restore invertebrate populations. Subsequent development of the concept has resulted in the creation of a mobile app. to facilitate wider participation in the survey by citizen scientists nationally.