Utilizing Existing Data to Measure Ecological Connectivity for Planning Southern Ontario’s Urban Growth: A Case Study of the Waterloo Region

Abstract

Urbanization is an increasing threat to global biodiversity. Urban areas are often thought to preclude native plants and animals but are capable of supporting some species if properly managed. Urban planning tends to focus on maximizing human benefits of the urban landscape; however, urban greenspaces can enhance ecological services for humans and promote natural species diversity. Habitat quantity and quality should be the top priorities when managing urban greenspaces. In urban areas, quantity and quality may be limited by the area available, so other tools are needed to make advancements. Connectivity represents a metric that could help plan urban greenspaces. To explore the utility of connectivity tools for cities in Southern Ontario, resistance maps were developed for Kitchener, Ontario based on four animals (bats, deer, shrews and snakes) using 2019 aerial data. Scenarios were developed based on potential changes to the city by increasing either the number of habitat cells by 5% or 10% (showing potential backyard and small greenspace restorations) or the number of buildings cells to meet projected growth targets. These were created by selecting cells randomly and reassigning values based on desired fragmentation of the land type. The resulting resistance maps were analyzed using an “omnidirectional” method developed for Circuitscape that enabled landscape level analysis of connectivity. Urban connectivity differed for the four species based on the dispersal capability of each species with bats and deer having the most connectivity with maximum resistance values of 0.53 and 0.76 respectively and shrews and snakes the least connectivity with maximum resistance values of 1.07 and 1.33. Connectivity decreased with increasing urbanization, showing a gradient of increasing current as building density increased and urban green spaces decreased. All urban greenspaces, from yards to natural areas, were important for landscape connectivity and need to be maintained if not enhanced. Buildings represented the primary barrier for all species other than bats (due to their ability to fly over them). Roads and paved areas also posed barriers to all species and represented the strongest barrier for bats. Mitigation methods should be considered for these areas, with greenspaces planned through highly built areas. Of the three models, increased building density had the largest effect on habitat connectivity, changing the resistance values by 25-33% for deer, shrew, and snakes. Bats species only had a 5-6% increase in resistance because buildings are less of a barrier to bats. The models with increasing habitat amounts were difficult to visually differentiate from the 2019 baseline, and changes in resistance value were less than 1%. These maps did show some benefits for urban species. This was expected due to the larger number of cells changed in the increased building density scenario. Planning mitigation efforts around densification should be the top priority for maintaining connectivity, but creating and maintaining greenspaces should not be forgotten as increasing habitat provides benefits beyond connectivity. Overall, these results were expected, but this analysis did show the utility of connectivity mapping for Kitchener. Connectivity analysis is potentially a valuable tool for urban planners in Southern Ontario cities if habitat quantity and quality are already being maximized and with the caveat that connectivity planning should not justify the removal of existing habitat patches and care should be taken to avoid undervaluing small patches.