Terrestrial transport infrastructures are known to have major negative impacts on species and ecosystem dynamics, leading to the alteration and fragmentation of habitats and landscape networks. Yet, they can also grow into new environments, thanks especially to the measures set up to mitigate their impacts. Originally built to prevent flooding, the stormwater ponds aim to limit the release into the natural environment of pollutants from the infrastructure, thus functioning as buffer zones. Nevertheless, scientists and practitioners are now observing the spontaneous use of these ponds by several species of amphibians. These species, which depend on both terrestrial and aquatic environments, are particularly sensitive to the quality and connectivity of their habitats.
This presentation, which follows a lightning talk held at ICOET 2017, offers to present the results of a thesis on the role that highway stormwater ponds can play for amphibians, as breeding habitat, but also as elements that can promote ecological continuities beneficial to these species.
The first part of the presentation will lay out the results of an analysis of the specific richness of 33 stormwater ponds located along a French highway and the factors that can influence this richness. This study, using a protocol based on environmental DNA, specifically focuses on the effects of the management practices (cleaning) implemented in highway ponds on their specific richness. It shows that highway ponds can host a great diversity of amphibian species and that cleaning practices have little impact on this specific richness when they are well adapted to the ecology of these species.
The second part will present the results of a modeling of amphibian ecological networks inspired by graph theory and designed to learn more about the role of stormwater ponds in these ecological networks. This study shows that some highway ponds, due to their locations, can provide alternative pathways for the dispersal of amphibians. Some can be used as « connecting sites » helping amphibians to cross the barrier that transport infrastructure stands as.
The outcome of this study supports the hypothesis put forth by several researchers stating that stormwater ponds are colonized by amphibians as a last resort, only when there are few natural aquatic sites available in the surrounding area.
This presentation will end with recommendations for highway infrastructure managers on how to deal with these species in and nearby the stormwater ponds they are in charge of.