Planning for the Green, Healthy Cities of the Future

With increased urbanization, urban environmental quality is rapidly deteriorating -- especially air quality from a variety of sources including trash/refuse burning and vehicular emissions -- with most of the rapid urbanization occurring in developing countries. As urban populations increase it is expected that sources of pollutants will do so as well, dramatically impacting air and water quality and community health. The WHO conservatively estimates that air pollution kills seven million people annually and the vast majority of these deaths occur in low-and middle-income countries. But the problem is not confined to the developing world: WHO's new Global Air Quality Guidelines documents the damage air pollution inflicts on human health, at even lower concentrations than previously understood. In 2019, 99% of the world population lived in places that did not meet WHO air quality guideline levels. Without intervention, mortality from outdoor air pollution could double by 2050. Environmental and human health and greenhouse gasses are most closely intertwined in cities. Some 75% of energy is consumed in cities, and 75% of global GHGs are produced in urban areas. How the developing world continues to urbanize without contributing to ever greater levels of pollution, particulate matter, and climate-forcing GHG emissions has yet to be adequately addressed. For example, urban trees in ten of the world’s megacities generate $482 million per year in health cost savings as a result of the reduction in pollutants. Parks, tree-lined streets, green roofs and walls mitigate the urban heat effect, reducing noise, air pollution and energy demand for cooling. Temperature differences of 7-15°C have been measured from tree shade and evapotranspiration. This, in turn, reduces not only the need for energy for mechanical cooling, but also reduces the negative health effects related to urban heat islands and air-borne pollutants. In the aftermath of disaster - human-made or natural - urban environmental quality is many times worse. Cancer-causing toxic building debris, noxious gases, and impaired water resources are just some of the challenges faced in reconstruction efforts. Even without counting post- disaster rebuilding, it is estimated that roughly 60 % of the area expected to be urban by 2050 has yet to be built. This presents a challenge and an opportunity. How can we build or rebuild cities so that we use fewer natural resources, provide basic urban services and a cleaner environment with limited financial resources? Laws and regulations requiring green spaces, low-carbon “well” buildings, material reuse and recycling, and cleaner forms of energy for transportation and power generation will help, but solutions need to be localized and cost-efficient to help the most vulnerable populations. We will need fast, innovative ways to design or redesign urban spaces, especially in growing peri-urban areas, that integrate a wide range of solutions for greener futures.

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