Urban planners are designing future cities with new levels of integration between land-use, travel network infrastructure, and green infrastructure. However, standard ecological models currently only inform the land-use part of that design process and so species that must forage, move, or disperse throughout the city along a green network are left unaccounted for in most network infrastructure plans. Because of this historical isolation between the grey and green aspects of urban design, they have been modeled, planned and implemented separately, and without much consideration for their interactions. We have developed an integrated platform that models the link between green and grey land-use according to the transport networks that connect them and uses that model to test several possible network configurations of green and grey integration. We believe that ideal network configurations will maintain the movement and dispersal of individuals both locally and across the entire network, and by maintaining this flow, they can make urban ecosystems more adaptive and resilient to global environmental change. We test this assertion by comparing the performance of dendritic fractal networks against nearest-neighbor reticulated web networks using both ecological (e.g. extinction, diversity, ecosystem function) and social (e.g. land price, job creation, commuter congestion) response metrics and focusing on Montreal, QC, Canada as our primary test case.
Results/Conclusions
Our results suggest that many of the long-debated tradeoffs between dendritic and reticulated networks also apply to designing green corridors in constrained urban landscapes. Reticulated networks can connect habitat patches using shorter direct routes and they are more resilient to perturbations, while dendritic networks maintain higher movement throughout the entire network and preserve structural complexity across more spatial scales. Reticulated networks frequently conflict with human transport networks and require specialized infrastructure to cross human transport, while the fractal topology of dendritic networks allows them to more-easily morph to existing built spaces to increase green infrastructure without impeding human transport networks. We conclude that dendritic corridor configurations may be best for most urban environments that are intrinsically dendritic but choosing growth over resilience will come at the cost of higher stochasticity in species abundance through time. Achieving dendritic corridor configurations will require designing corridors according to scale rather than just distance, with a few highway type corridors that are wide, long, and fast connected to many neighborhood corridors that are narrow, short, and slow.