Background information and definitions
Habitat destruction and fragmentation are important factors in the decline of amphibian populations. Small patches of habitat support smaller populations and if individuals are unable to move to other suitable areas, populations become isolated. This can make them more vulnerable to extinction. Restoring corridors of native vegetation between patches of suitable habitat may help to maintain amphibian populations.
Studies investigating the effects of restoring habitat connectivity with wildlife tunnels are discussed in ‘Threat: Transportation and service corridors – Install culverts or tunnels as road crossings’.
Supporting evidence from individual studies
A before-and-after study in 1994–2004 of a brackish and freshwater wetland in southern Tuscany, Italy (Scoccianti 2006) found that restoring connectivity between wetlands, by raising a road on a viaduct, significantly decreased deaths of migrating amphibians. Post-construction, many species were found migrating between wetlands under the viaduct. No remains of amphibians were found on the road post-construction, compared to thousands during some periods pre-construction. For example, after a night rainstorm in July 1997, over 6,500 newly emerged Italian edible frog Rana hispanica juveniles were counted on a 100 m stretch of road. A viaduct 215 m long was constructed in 2003 to raise the road. The supports of the viaduct (1.6 m high) were built on a bank 1 m higher than potential flood waters to prevent mixing of wetlands. Drift-fencing was installed for 300 m from each end of the viaduct along both sides of the road. Amphibian road kills were monitored before and after construction.Study and other actions tested