PS 48-241 - The heat is on: Thermal dynamics as a model for quantifying the complex linkages among urban ecosystem structure, function, and services in semi-arid cities.

Abstract: After massive heat waves across North America and Europe the past two years, scientists are receiving urgent calls to advise cities on how to mitigate climate change, the urban heat island effect, and increasing temperatures across urban ecosystems; however, more research is needed on heat, thermal exposure, and thermal perceptions at human-relevant scales. Urban ecosystem service assessments are limited by a similar problem with scale. They are dominated by predictive modeling of tree canopy benefits, and lack the quantifiable hyper-local evidence needed to inform planning, policy, and management. To address these two simultaneous challenges, we are studying thermal dynamics across semi-arid cities in the United States and Canada, as a model for quantifying urban ecosystem structure, function, and services at multiple scales and resolutions. Specifically, our goals are to: (1) Advance the quantification of ecosystem structure (e.g., land cover composition, configuration, and vertical heterogeneity) within strategic classes of management and ownership relevant to how cities are planned and maintained; (2) evaluate how ecosystem structure impacts biophysical outcomes using a variety of different measurements that represent thermal dynamics in cities at both large and hyper-local scales; (3) assess how these different measures of thermal dynamics translate into potential ecosystem service provisioning at hyper-local scales using indices of thermal comfort including Mean Radiant Temperature (MRT), Universal Thermal Climate Index (UTCI), and Physiological Equivalent Temperature (PET). Our results show that studying land cover composition and configuration in relationship to quantifiable biophysical outcomes, and specifically within localized strategic management units, leads to more applicable, impactful, and achievable management recommendations for transportation corridors and residential landscapes, than overarching tree canopy goals for entire cities. At hyper-local scales, moreover, metrics of urban landscape structure that capture land cover configuration and urban vertical complexity are more indicative of ecosystem functions and services than land cover composition alone. More focused quantitative research on urban structure and function linkages is needed to gain a comprehensive understanding of urban ecosystem services, their spatial distribution, and how we can maximize benefits provided by nature in cities. Urbanization is happening extensively in semi-arid cities globally. Without understanding how these ecosystems function at hyper-local scales, we will not be able to maximize ecosystem service provisioning in the face of climate change.