Sarah Raymond gives us information on her paper, “COVID-19 lockdowns and citizen science data reveal novel insights into species’ vulnerability to mortality on roads“, which was shortlisted for this year’s Elton Prize. We also hear a little about her story.

About the paper:

Roads are an integral and much-valued part of modern human society, but ecologically they represent a novel ecosystem, i.e. human-built, modified or engineered. Whilst roads can provide valuable movement corridors for both people and wildlife, they also pose a significant mortality risk to wildlife through collisions with vehicles. Wildlife-vehicle collisions (WVCs) occur in the many millions every single year, to the extent that they are one of the leading causes of anthropogenic mortality and population declines across wild species. WVC risk is however not equal for all species; previous observational studies have found that ecological traits can influence the likelihood of species being involved in WVCs, such as diet, body size and home range. Testing these observations is difficult because ideally a perturbation-style experiment would be needed that requires removing or reducing the number of vehicles on roads. That opportunity, however, was afforded by COVID-19 lockdown restrictions.

The COVID-19 pandemic saw strict lockdown restrictions imposed, including two major UK-wide lockdowns from March-May 2020 and December 2020-March 2021 (Fig. 1). This led to unprecedented, dramatic reductions in road traffic (by up to 50%) during these time periods (Fig. 1). The subsequent reduction in human activity was so pronounced that it caused a global quietening and has been coined the “anthropause”. These restrictions also limited some research activities, with many scientists unable to continue their typical fieldwork; however, a number of citizen science research projects, which rely on members of the public to submit data or carry out surveys, were still able to run. We therefore used citizen science WVC records from ‘The Road Lab’ project to carry out a perturbation-style study, exploring changes in WVC-risk as a result of the anthropause-induced reductions in traffic. We investigated which ecological traits received a reprieve during lockdowns and, therefore, identified the species at a higher risk of being involved in WVCs under normal traffic conditions.

On average, WVCs were 80% lower than would have been expected in a normal year; however, this was not surprising given the reduction in traffic and that citizen scientists were spending most of their time at home. Instead, we were most interested in whether there was a change in the relative frequency of WVCs involving species with certain traits during lockdowns compared to previous years (2014-2019). The inherent bias in comparing the absolute number of animals reported in and out of lockdowns therefore had to first be addressed, to avoid erroneous conclusions. For this, we used compositional data analysis to compare the relative proportions (i.e. the composition) of WVC occurrences in the different time periods.

During lockdowns we found proportionally fewer nocturnal mammals, animals that visit urban environments, mammals with high brain mass, and birds with long flight initiation distances (i.e. the distance at which they flee an oncoming threat – in this case, a vehicle) compared to the same time periods in previous years (Fig. 2). This suggests that species with these traits experienced a reprieve during lockdowns. The contrast, however, is that animals with these traits are likely to experience high levels of mortality under normal traffic conditions. Species with these traits include badgers, foxes and pheasants.

This study enabled us to understand which traits make species vulnerable on roads by seizing the opportunity of COVID-19 lockdowns, and associated reductions in vehicle use. The UK has ~39 million car owners, and 78% of all land is within just 1km of the 400,000km of roads that intersect the landscape. Given the extensive infrastructure that roads create, a natural next question to ask is ‘could anthropogenic infrastructure be acting as an evolutionary driver for certain species and traits?’ Identifying those ecological traits that lead to high WVC-risk is the first step to answering this question, and could help to identify more focused conservation efforts to reduce the impact of infrastructure on wildlife.

About the author:

Sarah Raymond is a final-year PhD student at Cardiff University with Dr. Sarah Perkins at ‘The Road Lab’. She is now in the final few months of her PhD, continuing to research the impacts of roads on wildlife, including through identifying roadkill hotspots and mapping the UK’s remaining ‘roadless areas’. She is looking to pursue postdoctoral research on wildlife interactions within linear infrastructure/novel ecosystems. Her broader research interests include spatial ecology, habitat connectivity/fragmentation, urban ecology and citizen science. In her spare time, Sarah particularly enjoys spending time in nature, hiking and surfing.