Susceptibility assessment of urban tree species in Cambridge, MA, from future climatic extremes

The City of Cambridge, Massachusetts, recognizes the value of the city’s urban forest in terms of air quality, lower wind speeds, esthetics, energy conservation, reduced noise pollution, habitat value, decreased runoff, and bolstering of local businesses and property values. The density, composition, and location of street and city park trees comprising the urban forest will be influenced by future climate-driven extreme weather events. In this study, we have developed an approach for assessing impacts of multiple extreme weather scenarios likely to become more frequent under climate change and subsequently influence the composition of street and park trees. This potential for loss of trees as a result of one (or more) of these climate-related extreme weather events is considered to be one indicator of the susceptibility of Cambridge’s urban forest to climate-related weather events. The scenarios considered were a hurricane/tropical storm similar to tropical storm Sandy in 2012, heat stress, snow or ice loading (e.g., loss of tree limbs), Asian longhorn beetle or emerald ash borer infestations, and the cumulative effect from the addition of all these scenarios. The literature was used to assess the sensitivity of tree species to each threat and determine the anticipated loss of individuals from each species. The results are a reasonable indication of the more tolerant tree species in Cambridge and their locations. This assessment of susceptibility can inform proactive management of the urban forest.