Open Collections

Abstract

Land development is a significant source of urban tree canopy decline despite requirements to protect and replant trees after project completion. Using remote sensing data, as well as public records, we studied tree retention and protection choices during land development in Surrey B.C. between 2009 and 2017. We found that canopy sharply declined during development but rebounded slightly in following years. Forested lands experienced the most pronounced canopy loss, while agricultural lands had few trees to begin with. Additionally, post-development urban forests were more diverse, but had more non-native species. Previously forested lands offered the most opportunity for protecting large, culturally significant trees. However, current policy focuses on individual trees, resulting in missed opportunities for conservation, including conservation of soils on agricultural land. In addition, we highlight the role tree protection zone shape and size contributes to potential success of tree preservation especially on previously forested land. Land use affected the size and shape of protection zones, which can affect tree survival. Larger tree protection zones and those with a rounded shape reduced the edge effect, likely resulting in less stress on retained trees. These were common on forested lands, but tree protection zones often deviated from a round shape, exposing protected trees to greater stress from root severance and light exposure. Overall, our analysis revealed land development had a homogenizing effect on urban forest composition and structure reducing resilience to future disturbances. Post-development urban forests had greater species diversity, greater fragmentation, and more small stature trees. Furthermore, our findings suggest legislation may contribute to this homogenization, by limiting the scope of resources assessed for preservation. Finally, we suggest that holistic site assessments that occur before building footprints are finalized will likely lead to more sustainable development practices.