Figure 1. Study area for this work, which is part of the Greening Research in Tacoma (GRIT) project, is located in South Tacoma, Washington, USA, shown by the black square on global map, where solar radiation shields (photographed) containing temperature loggers were installed on utility poles. Here we report on temperature data from loggers at 46 locations throughout the neighborhood (blue dots) during summer 2022.
Climate change is exacerbating the need for urban greening and the associated environmental and human well-being benefits. Trees can help mitigate urban heat, but more detailed understanding of cooling effects of green infrastructure are needed to guide management decisions and deploy trees as effective and equitable climate adaptation infrastructure. We investigated how urban trees affect summer air temperature along sidewalks within a neighborhood of Tacoma, Washington, USA, and to what extent urban trees reduce risks of high summer temperatures (i.e., the levels regulated by state outdoor heat exposure rules intended to reduce heat-related illnesses). Air temperature varied by 2.57 °C, on average, across our study area, and the probability of daytime temperatures exceeding regulated high temperature thresholds was up to five times greater in locations with no canopy cover within 10 m compared to those with 100% cover. Air temperatures decreased linearly with increasing cover within 10 m, suggesting that every unit of added tree cover can help cool the air. Our findings highlight the value of trees in mitigating urban heat, especially given expected warming with climate change. Protecting existing urban trees and increasing tree cover (e.g., by planting street trees), are important actions to enhance climate change resilience of urban areas.
Table 1. Example approaches for anticipating and adapting to climate impacts on terrestrial species.
Addressing the impacts of climate change on terrestrial species requires knowledge of how climates will change, how species will respond, and what is the scope of actions that can be taken to help species and systems adapt. There is a rapidly growing understanding of how species will respond to projected climatic changes with changes in their phenologies, distributions, population dynamics, interspecific interactions, and disease dynamics. Many management strategies have been proposed for addressing these changes, including general principles such as fostering resilience, practicing adaptive management, and expanding the scale of management as well as more specific recommendations such as increasing landscape connectivity and increasing the extent of reserve networks.