Risks and opportunities for wildlife living in road dominated environments. What pieces are missing to complete the puzzle?

Abstract

A Living on the roadside involves serious risks including restrictions to movements, disturbance of resting and feeding places, and roadkill menace. However, when crossing highly human modified areas such as simplified intensive agricultural landscapes or highly grazed areas, remnant natural habitats associated to roads (verges, roundabouts, bypasses, etc.) may be the only leftover natural areas acting as a last refuge for rare plants and small fauna. In these circumstances, there may be a positive contribution of roads and associated vegetated areas for biodiversity conservation may be considered. In Europe, remnants of natural habits on roadsides may be particularly relevant for the implementation of the “European Green Infrastructure” (EGI), defined as “… an interconnected network of green spaces in urban and infrastructure dominated environments that preserves the natural value and functions of the ecosystems and provide humans with the benefits associated with them”.However, to enhance the role of road vegetated marginal areas in the EGI there is still a long way to go and many fundamental questions need to be more deeply addressed:i) are road verges refuges or ecological traps for fauna?; (ii) what species traits makes them more suited to persist in road natural habitats remnants?; (iii) what is the relevance of verges as corridors?; (v) what surrounding landscape features are key to define the ecological role of road natural habitats remnants? What are the effects of roads on demographic parameters of populations living on the roadside? We have accessed the role of verges as providing foraging opportunities for bats, refuges and corridors for small mammals, and ecological traps for small mammal predators. We found that when roads cross lower suitable habitat, roads verges can be an important last remnant feeding habitat for bats. In highly grazed areas we have shown that verges are a critical refuge for small mammals, as important as riparian galleries, considered one of the most relevant habitats for fauna in the Mediterranean landscape. Using graph-theory-based connectivity metrics we demonstrated that verges contributed significantly more to the overall landscape connectivity than surrounding areas. This shows the high importance of verges as small mammal corridors, even in well preserved landscapes. We also show a strong positive association between locations of snakes, owls and mammal carnivores road casualties and the abundance on verges of wood mice and rabbits, the two main prey in the studied area. These results support the hypothesis that prey abundance on road verges may be a major driver explaining predator roadkills. In Portugal, road verges and other road remnants of natural habitats are estimated to cover more than 140 thousand hectares, an area larger than any terrestrial A Living on the roadside involves serious risks including restrictions to movements, disturbance of resting and feeding places, and roadkill menace. However, when crossing highly human-modified areas such as simplified intensive agricultural landscapes or highly grazed areas, remnant natural habitats associated to roads (verges, roundabouts, bypasses, etc.) may be the only leftover natural areas acting as a last refuge for rare plants and small fauna. In these circumstances, there may be a positive contribution of roads and associated vegetated areas for biodiversity conservation may be considered. In Europe, remnants of natural habits on roadsidesmay be particularly relevant for the implementation of the “European Green Infrastructure” (EGI) , defined as “… an interconnected network of green spaces in urban and infrastructure dominated environments that preserves the natural value and functions of the ecosystems and provide humans with the benefits associated with them”.However, to enhancethe role of road vegetated marginal areas in the EGI there is still a long way to go and many fundamental questions need to be more deeply addressed:i) are road verges refuges or ecological traps for fauna?; (ii) what species traits makes them more suited to persist in road natural habitats remnants?; (iii) what is the relevance of verges as corridors?; (v) what surrounding landscape features are key to define the ecological role of road natural habitats remnants? What are the effects of roads on demographic parameters of populations living on the roadside? We have accessed the role of verges as providing foraging opportunities for bats, refuges and corridors for small mammals, and ecological traps for small mammal predators. We found that when roads cross lower suitable habitat, roads verges canbe an important last remnant feeding habitat for bats.In highly grazed areas we have shown that verges are a critical refuge for small mammals, as important as riparian galleries, considered one of the most relevant habitats for fauna in the Mediterranean landscape. Using graph-theory-based connectivity metrics we demonstrated that verges contributed significantly more to the overall landscape connectivity than surrounding areas. This shows the high importance of verges as small mammal corridors, even in well preserved landscapes. We also show a strong positive association between locations of snakes, owls and mammal carnivores road casualties and the abundance on verges of wood mice and rabbits, the two main prey in the studied area. These results support the hypothesis that prey abundance on road verges may be a major driver explaining predator roadkills. In Portugal, road verges and other road remnants of natural habitats are estimated to cover more than 140 thousand hectares, an area larger than any terrestrial protected area in the country. Similar or larger areas of remnant habitats along roads occur in many other countries. Thus, gathering further knowledge aiming to quantify and identify their role in biodiversity conservation is key to properly offset road impacts on wildlife.