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Recent advances in data science and urban environmental health research utilise large-scale databases (100s–1000s of cities) to explore the complex interplay of urban characteristics such as city form and size, climate, mobility, exposure, and environmental health impacts. Cities are still hotspots of air pollution and noise, suffer urban heat island effects and lack of green space, which leads to disease and mortality burdens preventable with better knowledge. Better understanding through harmonising and analysing data in large numbers of cities is essential to identifying the most effective means of disease prevention and understanding context dependencies important for policy.

As the world becomes increasingly urbanised, there is recognition that public and planetary health relies upon a ubiquitous transition to sustainable cities. Disentanglement of the complex pathways of urban design, environmental exposures, and health, and the magnitude of these associations, remains a challenge. A state-of-the-art account of large-scale urban health studies is required to shape future research priorities and equity- and evidence-informed policies. The purpose of this review was to synthesise evidence from large-scale urban studies focused on the interaction between urban form, transport, environmental exposures, and health. This review sought to determine common methodologies applied, limitations, and future opportunities for improved research practice. Based on a literature search, 2958 articles were reviewed that covered three themes of: urban form; urban environmental health; and urban indicators. Studies were prioritised for inclusion that analysed at least 90 cities to ensure broad geographic representation and generalisability. Of the initially identified studies, following expert consultation and exclusion criteria, 66 were included. The complexity of the urban ecosystem on health was evidenced from the context dependent effects of urban form variables on environmental exposures and health. Compact city designs were generally advantageous for reducing harmful environmental exposure and promoting health, with some exceptions. Methodological heterogeneity was indicative of key urban research challenges; notable limitations included exposure and health data at varied spatial scales and resolutions, limited availability of local-level sociodemographic data, and the lack of consensus on robust methodologies that encompass best research practice. Future urban environmental health research for evidence-informed urban planning and policies requires a multi-faceted approach. Advances in geospatial and AI-driven techniques and urban indicators offer promising developments; however, there remains a wider call for increased data availability at local-levels, transparent and robust methodologies of large-scale urban studies, and greater exploration of urban health vulnerabilities and inequities.

Nature-based solutions (NBS) can deliver many benefits to human wellbeing, including some crucial to climate adaptation. We quantitatively assess the global potential of NBS strategies of protection, restoration, and agroforestry by modeling global climate change mitigation and local ecosystem services (water availability, sediment retention, runoff, pollination, nitrogen retention, green water storage, and coastal protection). The strategies with the most potential to help people do not necessarily deliver the most climate change mitigation: per area of conservation action, agroforestry provides substantial benefits (>20% increase in at least one local ecosystem service) to three times more people on average than reforestation while providing less than one tenth the carbon sequestration per unit area. Each strategy delivers a different suite of ecosystem service benefits; for instance, avoided forest conversion provides a strong increase in nitrogen retention (100% increase to 72 million people if fully implemented globally) while agroforestry increases pollination services (100% increase to 3.0 billion people if fully implemented globally). One common disservice shared by all the NBS strategies modeled here is that increased woody biomass increases transpiration, reducing annual runoff and in some watersheds negatively impacting local water availability. In addition, the places with the greatest potential for climate change mitigation are not necessarily the ones with the most people. For instance, reforestation in Latin America has the greatest climate change mitigation potential, but the greatest ecosystem service benefits are in Africa. Focusing on nations with high climate mitigation potential as well as high local ecosystem service potential, such as Nigeria in the case of reforestation, India for agroforestry, and the Republic of Congo for avoided forest conversion, can help identify win-win sites for implementation. We find that concentrating implementation of these three conservation strategies in critical places, covering 5.8 million km2, could benefit 2.0 billion people with increased local ecosystem services provision. These critical places cover only 35% of the possible area of implementation but would provide 80% of the benefits that are possible globally for the selected set of ecosystem services under the NBS scenarios examined here. We conclude that targeting these critical places for protection, restoration, and agroforestry interventions will be key to achieving adaptation and human wellbeing goals while also increasing nature-based carbon mitigation. [ABSTRACT FROM AUTHOR]

An extensive area of frequently mowed open grassy roadsides is designed for highway safety, yet paradoxically, in many locations woody vegetation of various types may make safer highways, and additionally provide diverse valuable benefits for society. Therefore our objective is to identify the goals of greatly increasing woody vegetation, consider the pros and cons, and identify the especially desirable and undesirable locations for it. Today, frequent costly roadside mowing favors many non-native species including invasives. Rare species also live on roadsides, including nearly a quarter of the U.S. federally listed threatened-and-endangered plant species with at least one roadside population. The prime goals of greatly increasing woody roadside vegetation are to: (1) increase wildlife habitat, biodiversity, and landscape connectivity; (2) increase highway safety and driver experience; and (3) decrease pollut¬ant and peak-water-flow inputs to nearby water-bodies. The first goal has few disadvantages and also accomplishes diverse societal benefits. The second goal emerges from a modest decrease in vehicle speed in appropriate areas, plus the use of visually diverse types of roadside woody vegetation. An entrée into the travel-behavior and wildlife literature indicates that drivers drive more slowly on narrow than wide two-lane highways, and suggests that a sharp drop in wildlife/vehicle crashes appears between a posted speed limit of 90 and 70 km/hr (55 and 45 mph). The third goal enhances nearby streams, ponds, and other water bodies, mainly by significantly improving conditions in roadside ditches. Tall shrubs or natural forest/woodland are especially desirable vegetation types for >50% of the 35 situations common along road networks. Mowed grass is especially desirable on 17% of the situations, essentially the most risky driving locations. Meadow/low shrubs and small trees with herbaceous layer are intermediate in overall roadside value. We conclude that a massive increase in woody roadside vegetation offers numerous transportation, environmental, and societal benefits with minor disadvantages. Evaluation by a blue-ribbon panel of diverse experts and widespread pilot projects with research and monitoring are valuable next steps.