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Strategies for restoring ecological connectivity and establishing wildlife passage for the upgrade of Route 78 in Swanton, Vermont: an overview

  • Author(s): Austin, John M.
  • Ferguson, Mark
  • Gingras, Glenn
  • Bakos, Greg
  • et al.
Abstract

Vermont Route 78 travels through one of the largest and most significant wetland complexes in the State of Vermont. This fact is exemplified by the presence of the Missisquoi National Wildlife Refuge and the Carmens Marsh State Wildlife Management Area as the primary landowners of this large wetland system. This mosaic of wetlands offers outstanding wildlife habitat for a myriad of resident and migratory species ranging from waterfowl (e.g., black ducks, wood ducks, goldeneyes) and wading birds (e.g., great blue herons, American bitterns, Virginia rail – the state’s largest colony of nesting great blue herons occurs in this wetland system), to rare, threatened and endangered species, such as the black tern and spiny softshell turtle. Although black bear and moose are not the common species in this part of the state, vehicle collisions with those species have occurred in the project area. Each year, many white-tailed deer are killed by vehicle collisions in one area of this roadway alone. Numerous other species of mammals, birds, reptiles and amphibians are killed by traffic in this area each year. Route 78 is a relatively narrow, winding road with an increasing volume of traffic, most notably commercial truck traffic coming from and going to Canada. Public safety concerns regarding the high traffic volume and poor road conditions have caused the Vermont Agency of Transportation to pursue upgrade of the road along the Missisquoi River and through the Mississquoi wetland system and Missisquoi National Wildlife Refuge. In order to address safety issues related to the road conditions and the wildlife habitat and associated environmental concerns, a collaborative process was developed to identify issues and solutions. The Vermont Department of Fish and Wildlife in coordination with the Missisquoi National Wildlife Refuge and the Vermont Agency of Transportation identified impacts to wetland habitat, effects of traffic on sensitive wetland-dependent wildlife, and the barrier effect of the existing road conditions as primary concerns related to this project. In order to address those concerns, we evaluated landscape and habitat conditions along the road project corridor, distribution of road-related wildlife mortality, animal movement information based on evidence of animal movements and activity in habitats near the road (e.g., tracks, observations of animals), and local knowledge of animal movements and animal vehicle collision areas from Missisquoi National Wildlife Refuge biologists and Vermont Department of Fish and Wildlife Game Wardens. Landscape analysis of this segment of Route 78 indicates an isolated area of upland habitat surrounded by wetland habitat associated with an S-curve in the road known as Louis Landing. Road-related wildlife mortality information indicates a high proportion of animal-vehicle collisions along the S-curve by Louis Landing suggesting that the upland habitat is serving as a primary travel corridor for many species of wildlife. Species that cross, or are likely to cross, within the wetland/upland complex along Route 78, such as deer, moose, black bear, mink, otter, beaver, muskrat, raccoon, coyotes, red fox, gray fox, other small mammals, amphibians, reptiles, and some birds, would utilize a transition zone between wetland and upland habitat which is provided by this area. As mentioned earlier, this is the only area where black bear and moose have tried to cross Route 78. In Vermont, we have found black bears are selective in their preference for locations to cross roads. This is a primary location where birds are struck by vehicles, including hawks, owls, waterfowl and songbirds. Additionally, we identified several other important wildlife linkage areas that traverse Route 78 as well as an important amphibian breeding area that requires large migrations of frogs to cross the road each year during spring spawning season. Based on this evaluation, we developed a “Route 78 Permeability Plan for Fish, Wildlife, and Ecosystem Functions.” The purpose of this plan is to identify the most significant wildlife habitat linkage areas along the road project corridor and identify measures for resolving road-related conflicts with those areas. The plan proposes the following measures for restoring and mitigating wildlife movement and ecological functions within the Missisquoi wetland system: A. Construction of a 500-foot-long span bridge in an area identified as Louis Landing. This is the primary linkage area. The dimensions of the underpass have been designed to accommodate spanning the entire linkage area to accommodate the needs of a variety of taxa and species. We believe that this strategy will reduce the risk that the structure would fail to serve the needs and interests of some of the species and/or taxanomic groups that require unrestricted movement in this wetland system. B. Shifting of the existing road at least 100 feet away from the edge of the Missisquoi River and restore that area to functional riparian habitat.

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