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As urbanization claims more of the planet, road networks usually expand, and traffic usually increases along with them. Wildlife is not always given full consideration when roads and highways are constructed, especially within city limits.

U of T News asked Namrata Shrestha, adjunct professor at the School of the Environment, about her research on roads and ecology in urban landscapes, and how it can guide policy, planning and the design stages of a road network.

Why is your work important?

Green space (or natural areas as some prefer to call it) is critical to maintaining a healthy landscape both for human and non-human species. It provides habitat for critters and diverse plants, and provides us with clean air and water among other things. As urbanization continues, green spaces are often compromised either in terms of area or quality. This has negative consequences on the natural processes that are important for all life. Science has provided us with ways to identify these consequences, and methods to avoid or mitigate them where it matters for long-term resiliency of the landscape. As we continue to build more cities and change land for human use, it is critical to apply these understandings if we are to ensure a sustainable and resilient future for the planet. 

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What happens when roads and bridges start crisscrossing urban wildlife habitats?

Maintaining a healthy and functioning wildlife habitat in urban areas such as Toronto is challenging. Directly and indirectly, urbanization may compromise the ability of a green space to function as a habitat for wildlife. Road network, as well as any linear infrastructure, can have multiple impacts on the otherwise intact and functional habitat. Building roads results in habitat loss and disturbance throughout the construction phase and beyond. After construction, they fragment the habitat into smaller pieces structurally and also pose a functional barrier to wildlife movement, especially when traffic is high, so that animals cannot get to their resources to complete their life cycle needs, such as food and breeding.

Also, when roads cross the habitat this often leads to wildlife-vehicle collisions resulting in road kills. Lastly, road salt and noise levels also compromise the habitat function in urban greenspaces. All of the above cumulatively affect the wildlife population negatively and may result in extirpation of the sensitive ones from the landscape unless appropriate measures are taken to avoid, minimize, and mitigate these impacts.

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How do you ensure safe animal mobility in urban areas?

Animal mobility in urban areas is important not just for the sake of animals themselves but for human safety as well. We don’t want wildlife-vehicle collisions that may be fatal for human beings in addition to widespread road mortality of animals. That’s why it is important to plan and design our infrastructure, especially linear ones like roads and rails, in ways that can minimize, if not avoid posing barriers for safe wildlife passage. We can do so through proper understanding of our landscape and knowing where animal movements are most likely and then taking appropriate measures to facilitate animal movement in strategic locations. 

What sorts of measures?

They can include a wide variety of options depending on the location. If there are areas that are more sensitive than others, such areas should remain roadless and alternative alignments should be explored. In other areas roads can be designed in such a way that barriers to wildlife and road kills are minimized using well-designed eco passages (culverts, as well as bridges). Also, if animal movement is more likely in a certain time of year then seasonal road closures can be considered. Likewise, road salt and noise barriers also need to be rethought if we intend to maintain the functionality of green space as the wildlife habitat.

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