Road ecology blog: wildlife fencing and wet and dry culverts, Rio de Janeiro, Brazil
Road ecology blog: wildlife fencing and wet and dry culverts, Culvert under -park road- (estrada-parque) Capelinha-Mauá (RJ-163), near Resende, Rio de Janeiro, Brazil.
The wildlife fencing only covers a few hundred meters with a wet and a dry culvert in the middle. For large ungulates, specifically Cervidae, wildlife fencing is most effective in reducing collisions if at least 5 km of road length is fenced. While the minimum recommended length may be shorter for South American mammals, a few hundred meters appears really short and it is unlikely to result in a substantial reduction of large mammal-vehicle collisions.
The wet and dry culvert indicate that hydrology, aquatic wildlife and terrestrial wildlife may all have been considered during the design stage. However, rather than having one structure for wet habitat and a second structure for dry habitat, it is better to provide one larger structure that is not only designed for hydrology and aquatic wildlife, but also for semi-aquatic and terrestrial wildlife. A larger structure can allow for extreme precipitation events, reduce the probability that the culvert will be blocked by debris, and it can provide aquatic, riparian and terrestrial habitat for a wide range of species. It is best to have a bottomless culvert or bridge that allows for natural stream dynamics and natural habitat inside the culvert or under a bridge. In addition, it is important to specify the target species and design the dimensions of the crossing structures accordingly. For example, should tapir (Tapirus terrestris) have been among the target species, the size of the structures below is completely inadequate; tapirs would not even remotely fit in the culverts.
Click here for images of wildlife fencing.
Click here for images of multifunctional underpasses.
Click here for images of wildlife underpasses.
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Image below: dry culvert on upper left, wet culvert on lower right.
