Habitat fragmentation: Impacts of road and trails

Habitat fragmentation: Impacts of road and trails Roads, trails, fences, and other barriers can isolate habitat and populations of reptiles and amphibians, and this fragmentation can lead to inbreeding, increased mortality, and isolated population extinctions (Williams et al. 2017). Roads can contribute pollutants to adjacent streams and wetlands, and roads and trails may provide corridors for invasive species (Kingsbury and Gibson 2012). Eastern box turtles and most amphibians are particularly susceptible to road mortality. One 17-month study in Celery Bog near West Lafayette, Indiana recorded nearly 8,000 amphibian road mortalities along a 1.5 mi (km) stretch of road (Glitsa et al. 2007).

There are two main, paved roads that bisect and border the Preserve, N. Headley Rd. and N. Dunn St. Habitat is located adjacent to these roads, including Griffy Lake, seasonal mudflats, and emergent marsh near Headley Rd., and the wet old field near Dunn St. We observed a dead eastern milk snake and a dead broad-headed skink on N. Headley Rd that appeared to be hit by vehicles. We also observed Cope’s gray tree frogs breeding in the puddles and pools of the parking area north of the dam. These frogs likely cross Dunn St from nearby woodland to reach these pools.

In order to mitigate risk of road mortality in the Preserve, temporary measures such as reduced speed limits and cautionary signage alerting motorists to reptile and amphibian migration during the breeding season may result in decreased mortality and encourage motorists to avoid hitting wildlife (Kingsbury and Gibson 2012). More permanent measures such as installing speed bumps or a combination of fencing and underpasses can be used to funnel wildlife safely across roads. There is one culvert under N Headley Rd that likely allows aquatic species like turtles to cross under the road, but this conduit is dependent on water levels and debris within the pipe that could block passage. Monitoring of the pipe and its ability to allow unobstructed passage may be useful in gauging the effectiveness of an existing underpass.

The Preserve is proposing construction of 5.7 mi (9.2 km) of a new loop trail around the Preserve, which may pose some risk to reptiles and amphibians. Risks include increased erosion, sedimentation, and habitat fragmentation. Erosion and sedimentation can result from trail construction on ridges, and may damage or fill in vital habitat for amphibians downhill. Ephemeral pools are particularly vital for salamander populations most as larvae cannot survive in wetlands with established fish populations.

In order to mitigate this risk we recommend that the new trail is located away from sensitive habitats. Additionally, care should be taken when deciding the path of trails to avoid habitat fragmentation. We recommend trail construction happen in small phases, silt fencing or filter socks are used during the construction process, and exposed soil is seeded as soon as construction is complete. Using best management practices and adequate buffers to prevent sediment or pollution from flowing downhill will protect sensitive sites. Planting native forbs and grasses, and mulching can minimize soil erosion and invasive species encroachment as well. Wildlife friendly soil stabilization measures, rather than traditional mesh, is safer for reptiles and amphibians because larger holes can allow passage instead of entrapment and death (Kingsbury and Gibson 2012).