Britain's landscape is highly fragmented by roads, with researchers from Cardiff University finding that more than 70% of the UK's roadless areas are smaller than 1 km2.
The researchers say that more than 60% of roadless patches in the UK are smaller than the typical area many common UK mammals needs to survive, meaning species such as badgers and red foxes likely face a high risk of wildlife-vehicle collisions.
Dr Sarah Raymond, who completed the work during her PhD at Cardiff University School of Biosciences, said: "Roads cover 20% of land globally, fragmenting land into almost 600,000 patches.
"Because of this, roads have a wide range of impacts on wildlife, including reduced habitat connectivity and wildlife-vehicle collisions. Wildlife-vehicle collisions are estimated to cause millions of animal mortalities on roads every year and are a leading cause of population decline and biodiversity loss."
Analysing roadless areas is important for identifying areas of ecological value and intensifying conservation efforts.
The researchers extracted and mapped roads across Great Britain from OpenStreetMap, an open-access geographic database, to calculate roadless areas in Great Britain. Both areas covered by roads and 'road effect zones' - the areas around roads that experience ecological effects - were mapped. The roadless areas were defined as patches of land unaffected by roads, beyond the road effect zones.
The researchers found that the total number of roadless patches across Great Britain was 6,138 with a 1km road effect zone, 29,164 with a 500m road effect zone, and 93,561 with a 100m road effect zone. The majority (71-74%) of roadless patches were smaller than 1km² in size, and a small minority (0.002-0.014%) were greater than 100km2.
Roadless patches were significantly larger in Scotland than England and Wales, with Scotland having the greatest percentage of roadless area and larger individual patches, primarily coinciding with the Scottish Highlands and Cairngorms National Park. England had the largest number of individual patches, but the lowest overall percentage of land that is roadless.
The researchers found that 53% of all roadless areas were not covered by existing protected habitat designations, highlighting a need to increase protection of roadless areas and connectivity between them.
Dr Perkins, who runs Road Lab at Cardiff University, added: "Nearly half (47%) of roadless areas overlap with existing protected sites, but often only partially. Protecting and connecting roadless areas offers a practical route to expanding our protected area network while reducing wildlife‑vehicle collisions."
This work provides the first step to help us see where improvements in connectivity could be made for the benefit of biodiversity.
The findings of the study emphasise the extent to which Great Britain is fragmented by roads and the extent of their effects.
"The European badger has a home range greater than the majority - 73% - of roadless patches, putting them at high risk of wildlife-vehicle collisions compared to other species with smaller home ranges," added Dr Raymond.
Future research could focus on identifying priority areas for practical interventions, and on improving our understanding of the long-term and future effects of roads on wildlife populations.
The research, Quantifying roadless areas and fragmentation in the context of wildlife-vehicle collision risk in Great Britain, was published in Scientific Reports.
