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Abstract: The Pittsburgh Metropolitan Region in Western Pennsylvania, U.S., like many cities glob-ally, historically has an inequitably distributed urban forest and faced street tree biodiversity challenges. Additionally, Pittsburgh faces several barriers and threats to maintaining and expanding its urban tree cover, including pests, diseases, social acceptance, built environment obstacles, and climate change. To address these concerns, in 2012, Pittsburgh created an Urban Forest Master Plan setting equitable forest cover and biodiversity benchmarks. This paper documents the status of achieving these benchmarks and uses microclimate simulations to assess the capacity of these benchmarks in mitigating future mean radiant temperatures. Results demonstrate that the story of Pittsburgh’s urban forest cover, street tree biodiversity, and age diversity is complex, but inequities are primarily driven by income. However, if Pittsburgh can achieve its forest cover benchmarks, it can reduce its neighbourhoods’ 2050 mean radiant temperature below 2010 temperatures, even under climate change-fuelled extreme heat events. The process and results reported in this paper allow designers and decision-makers to calibrate localized urban forest benchmarks more effectively based on various future scenarios while ensuring the equitable distribution of heat mitigation. 

The evolutionary shift from a single-element ear, multi-element jaw to a multi-element ear, single-element jaw during the transition to crown mammals marks one of the most dramatic structural transformations in vertebrates. Research on this transformation has focused on mammalian middle-ear evolution, but a mandible comprising only the dentary is equally emblematic of this evolutionary radiation. Here, we show that the remarkably diverse jaw shapes of crown mammals are coupled with surprisingly stereotyped jaw stiffness. This strength-based morphofunctional regime has a genetic basis and allowed mammalian jaws to effectively resist deformation as they radiated into highly disparate forms with markedly distinct diets. The main functional consequences for the mandible of decoupling hearing and mastication were a trade-off between higher jaw stiffness versus decreased mechanical efficiency and speed compared with non-mammals. This fundamental and consequential shift in jaw form–function underpins the ecological and taxonomic diversification of crown mammals. This article is part of the theme issue ‘The mammalian skull: development, structure and function’.