Enhancing Habitat Connectivity Through Computer Modeling
Alongside the climate crisis, the world is facing massive biodiversity loss. One of the main causes is the destruction and degradation of habitats. Human infrastructure, such as buildings, lawns, or roads, are barriers to the movement of wild animals and may separate wild habitats. This can reduce ecosystem health and impact wild animal populations.
When making infrastructure decisions, however, ecological factors are usually neglected in favor of cost and land use priorities. This article presents a method to address this problem. The researchers used computer modeling to identify areas separating habitats and suggested solutions to reconnect them.
The study analyzed the possible movement of four-toed salamanders in a 13,000-hectare region called the Oak Ridge Reservation in Tennessee. They focused on this salamander as it is threatened in several locations and is sensitive to habitat changes. The researchers focused on various management strategies, including installing new culverts and replacing or restoring old ones. Culverts are tunnels that animals can use to move between habitats separated by infrastructure.
Their model compared three scenarios of connectivity: (1) removing road barriers, (2) restoring the habitat around the ends of existing culverts, and (3) replacing pipe culverts with open-bottom ones. Four-toed salamanders prefer to move through open-bottom culverts, which have a natural substrate floor instead of plastic, metal, or concrete.
To generate data, the computer model had to be prepared in two steps. First, the researchers counted adult salamanders and larvae in wetlands to locate the breeding sites, which they identified as important habitats that should be connected. Next, they generated a map called a resistance surface. Each map location gets a resistance value, depending on how difficult it is for animals to move across the landscape. The more impassable, the higher the resistance value.
Once the resistance surface was set up, the authors found that 80% of the strongest infrastructure barriers affecting salamanders were non-road barriers, such as power lines and large mowed areas. After simulating the different scenarios (1-3), the authors demonstrated that if 5% of road barriers with the most negative impact on salamanders were removed, the habitats would be 31% more connected. However, this means removing over 400 roads, which is likely infeasible.
The authors suggested other, more feasible ways to increase salamander habitat connectivity. For example, connectivity could increase by 38% if the area around the ends of 23 culverts in the Oak Ridge Reservation were restored to a natural habitat (modeled in scenario 2). A drawback of this scenario is that it would require a lot of resources in terms of restoration work.
Finally, scenario 3 involved replacing existing pipe culverts with open-bottom culverts. The authors found that upgrading the 10 most important pipe culverts would increase salamander habitat connectivity by 35%.
Computer modeling is a powerful tool to inform decision-making when it comes to protecting wild animals and reducing costs and labor. Although this was a case study of four-toed salamanders in one region, computer monitoring tools may be applied to other species and other contexts. Furthermore, it’s possible that connecting salamander habitats can also benefit other species. A key lesson for animal advocates is that it’s possible to include wild animal interests when making infrastructure decisions. New and emerging technology may make this easier.