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Abstract Trees in residential environments are affected by a unique combination of environmental and anthropogenic factors, including occasional insect outbreaks that are increasing in frequency and severity due to climate change. We studied loblolly pine trees infested by bark beetles in a residential backyard in a southeastern US city. We investigated the responses of tree and stand‐level transpiration to environmental factors (solar radiation, atmospheric vapor pressure deficit, and soil moisture), severe weather events (strong winds and heavy storms), bark beetle infestation, and human actions (insecticide treatments and tree removals). We used constant heat dissipation probes to make continuous sap flux measurements (J₀) in tree boles. Over 22 months of the study,J₀of trees with confirmed infestation decreased from ~90 to ~60 g cm⁻² day⁻¹andJ₀of the rest of the trees increased from ~60 to ~80 g cm⁻² day⁻¹. One infested tree died, as itsJ₀steadily declined from 110 g cm⁻² day⁻¹to zero over the course of 2 months, followed by a loss of foliage and visible signs of severe infestation 6 months later.J₀was sensitive to variations in incoming solar radiation and atmospheric vapor pressure deficit. In most trees,J₀linearly responded to soil water content during drought periods. Yet despite complex dynamics ofJ₀variations, plot‐level transpiration at the end of the study was the same as at the beginning due to compensatory increases in tree transpiration rates. This study highlights the intrinsic interplay of environmental, biotic, and anthropogenic factors in residential environments where human actions may directly mediate ecosystem responses to climate. 

Urban forests provide ecosystem services important for regulating climate, conserving biodiversity, and maintaining human well‐being. However, these forests vary in composition and physiological traits due to their unique biophysical and social contexts. This variation complicates assessing the functions and services of different urban forests. To compare the characteristics of the urban forest, we sampled the species composition and two externally sourced traits (drought tolerance and water‐use capacity) of tree and shrub species in residential yards, unmanaged areas, and natural reference ecosystems within six cities across the contiguous US. As compared to natural and unmanaged forests, residential yards had markedly higher tree and shrub species richness, were composed primarily of introduced species, and had more species with low drought tolerance. The divergence between natural and human‐managed areas was most dramatic in arid climates. Our findings suggest that the answer to the question of “what is an urban forest” strongly depends on where you look within and between cities. 

Many of the world’s major cities have implemented tree planting programs based on assumed environmental and social benefits of urban forests. Recent studies have increasingly tested these assumptions and provide empirical evidence for the contributions of tree planting programs, as well as their feasibility and limits, for solving or mitigating urban environmental and social issues. We propose that current evidence supports local cooling, stormwater absorption, and health benefits of urban trees for local residents. However, the potential for urban trees to appreciably mitigate greenhouse gas emissions and air pollution over a wide array of sites and environmental conditions is limited. Consequently, urban trees appear to be more promising for climate and pollution adaptation strategies than mitigation strategies. In large part, this is due to space constraints limiting the extent of urban tree canopies relative to the current magnitude of emissions. The most promising environmental and health impacts of urban trees are those that can be realized with well-stewarded tree planting and localized design interventions at site to municipal scales. Tree planting at these scales has documented benefits on local climate and health, which can be maximized through targeted site design followed by monitoring, adaptive management, and studies of long-term eco-evolutionary dynamics. 

Societal Impact Statement It is increasingly common for plant scientists and urban planning and design professionals to collaborate on interdisciplinary teams that integrate scientific experiments into public and social urban spaces. However, neither the procedural ethics that govern scientific experimentation, nor the professional ethics of urban design and planning practice, fully account for the possible impacts of urban ecological experiments on local residents and communities. Scientists that participate in design and planning teams act as decision‐makers, and must expand their domain of ethical consideration accordingly. Conversely, practitioners who engage in ecological experiments take on the moral responsibilities inherent in generation of knowledge. To avoid potential harm to human and non‐human inhabitants of cities while maintaining scientific and professional integrity in research and practice, an integrated ethical framework is needed for urban ecological planning and design. SummaryWhile there are many ethical and procedural guidelines for scientists who wish to inform decision‐making and public policy, urban ecologists are increasingly embedded in planning and design teams to integrate scientific measurements and experiments into urban landscapes. These scientists are not just informing decision‐making – they are themselves acting as decision‐makers. As such, researchers take on additional moral obligations beyond scientific procedural ethics when designing and conducting ecological design and planning experiments. We describe the growing field of urban ecological design and planning and present a framework for expanding the ethical considerations of socioecological researchers and urban practitioners who collaborate on interdisciplinary teams. Drawing on existing ethical frameworks from a range of disciplines, we outline possible ways in which ecologists, social scientists, and practitioners should expand the traditional ethical considerations of their work to ensure that urban residents, communities, and non‐human entities are not harmed as researchers and practitioners carry out their individual obligations to clients, municipalities, and scientific practice. We present an integrated framework to aid in the development of ethical codes for research, practice, and education in integrated urban ecology, socioenvironmental sciences, and design and planning. 

Abstract Water smart cities are increasing their use of irrigation and misting to cope with extreme heat and drought. This is being enabled by widespread use of rainwater tanks, stormwater capture and storage systems, and recycled sewage wastewater to irrigate street trees as well as private and public green spaces. These alternative water resources provide new options for cities to better withstand and function under extreme summer heatwave conditions with little or no impact on drinking water supplies. Small‐scale approaches to evaporatively cool urban animals, vegetation habitat, and people are showing initial success. However, ongoing testing and modeling are needed to understand the impacts of scaling up these interventions and to evaluate their cost‐effectiveness. We describe current innovations in irrigation of Australian cities to help policy development in other countries and cities experiencing similar climates with episodic summer heatwaves.