Climate adaptation is being embraced by many municipalities worldwide. An element of this is the planting and protection of urban trees. However, the fact that climate change will also have an impact on urban trees has been largely overlooked. We argue that climate vulnerability assessments are necessary for addressing climate adaptation in urban forests and contribute to successful climate adaptation in cities. We review and integrate the literature on climate vulnerability and urban forests to explore how the general notion of urban forest vulnerability to climate change can be developed into an operational framework for undertaking a vulnerability assessment. The framework characterizes climate exposure, impact, sensitivity, and adaptive capacity, as well as nonclimatic drivers and factors, in urban forests. The most important themes in this discussion include urban tree species selection and diversity, naturalization, resource access, social awareness and engagement, budget and economic valuation, liability issues, and governance structures. Climate change vulnerability assessments help us understand how and why urban forests are vulnerable to climate change, identify future areas for research, and determine what adaptation measures could be included in urban forest management. These assessments help bring climate change to the forefront of the decision-making process and contribute to successful urban adaptation to climate change.

We argue that a healthy urban forest contributes immensely to the sustainability of cities. The argument is based on a comprehensive array of values elicited from Canadians in several cities. To begin, we define the urban forest as inclusive of all the trees in the city and thus representing the predominant contributor to a city’s green infrastructure. Then we enumerate and explain the broad diversity of ways in which urban people value trees in the city. We, thus, show the myriad pathways by which trees contribute positively to any city’s social, economic, and ecological sustainability. Following a short summary of the ways in which trees may detract from people’s quality of life, we present promising management directions for urban-forest improvement, as we understand the situation in Canada. We conclude that all cities can enhance their sustainability by improving the urban forest.