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Climate Change and the American City  

Andrew Hurley

American cities developed under relatively quiescent climatic conditions. A gradual rise in average global temperatures during the 19th and 20th centuries had a negligible impact on how urban Americans experienced the weather. Much more significant were the dramatic changes in urban form and social organization that meditated the relationship between routine weather fluctuations and the lives of city dwellers. Overcoming weather-related impediments to profit, comfort, and good health contributed to many aspects of urbanization, including population migration to Sunbelt locations, increased reliance on fossil fuels, and comprehensive re-engineering of urban hydrological systems. Other structural shifts such as sprawling development, intensification of the built environment, socioeconomic segregation, and the tight coupling of infrastructural networks were less directly responsive to weather conditions but nonetheless profoundly affected the magnitude and social distribution of weather-related risks. Although fatalities resulting from extreme meteorological events declined in the 20th century, the scale of urban disruption and property damage increased. In addition, social impacts became more concentrated among poorer Americans, including many people of color, as Hurricane Katrina tragically demonstrated in 2005. Through the 20th century, cities responded to weather hazards through improved forecasting and systematic planning for relief and recovery rather than alterations in metropolitan design. In recent decades, however, growing awareness and concern about climate change impacts have made volatile weather more central to urban planning.


Communicating About Climate Change with Urban Populations and Decision-Makers  

Eric Chu and Todd Schenk

Cities are important venues for climate change communication, where global rhetoric, national directives, local priorities, and media discourses interact to advance mitigation, adaptation, and resilience outcomes on the ground. Urban decision makers are often directly accountable to their electorates, responsible for the tasks most relevant to advancing concrete action on climate change, and flexible in pursuing various public engagement programs. However, many cities are designing climate policies without robust downscaled climate projections or clear capacity and support mechanisms. They are often constrained by fragmented governance arrangements, limited resources, and jurisdictional boundaries. Furthermore, policies often fall short in responding to the disparate needs of heterogeneous urban populations. Despite these constraints, cities across the global North and South are innovating with various communication tools to facilitate public awareness, political engagement, context-specific understanding, and action around climate change. These tools range from traditional popular media to innovative participatory processes that acknowledge the interests of different stakeholders, facilitate engagement across institutional boundaries, and address persistent scientific uncertainty through information coproduction and knowledge reflexivity. By selectively employing these tools, local governments and their partners are able to translate climate science into actionable mitigation, adaptation, and resilience plans; prioritize decision making while taking into account the multiscaled nature of urban infrastructures and service provisions; and design adaptable and flexible communication processes that are socially equitable and inclusive over the long term.


Urban Heat Islands and Their Associated Impacts on Health  

Clare Heaviside

Towns and cities generally exhibit higher temperatures than rural areas for a number of reasons, including the effect that urban materials have on the natural balance of incoming and outgoing energy at the surface level, the shape and geometry of buildings, and the impact of anthropogenic heating. This localized heating means that towns and cities are often described as urban heat islands (UHIs). Urbanized areas modify local temperatures, but also other meteorological variables such as wind speed and direction and rainfall patterns. The magnitude of the UHI for a given town or city tends to scale with the size of population, although smaller towns of just thousands of inhabitants can have an appreciable UHI effect. The UHI “intensity” (the difference in temperature between a city center and a rural reference point outside the city) is on the order of a few degrees Celsius on average, but can peak at as much as 10°C in larger cities, given the right conditions. UHIs tend to be enhanced during heatwaves, when there is lots of sunshine and a lack of wind to provide ventilation and disperse the warm air. The UHI is most pronounced at night, when rural areas tend to be cooler than cities and urban materials radiate the energy they have stored during the day into the local atmosphere. As well as affecting local weather patterns and interacting with local air pollution, the UHI can directly affect health through heat exposure, which can exacerbate minor illnesses, affect occupational performance, or increase the risk of hospitalization and even death. Urban populations can face serious risks to health during heatwaves whereby the heat associated with the UHI contributes additional warming. Heat-related health risks are likely to increase in future against a background of climate change and increasing urbanization throughout much of the world. However, there are ways to reduce urban temperatures and avoid some of the health impacts of the UHI through behavioral changes, modification of buildings, or by urban scale interventions. It is important to understand the physical properties of the UHI and its impact on health to evaluate the potential for interventions to reduce heat-related impacts.


Climate Change Impacts on Cities in the Baltic Sea Region  

Sonja Deppisch

While not all projected climate change impacts are affecting especially and directly at all the cities of the Baltic Sea region (bsr), including its basin, those cities expect very different direct as well as indirect impacts of climate change. The impacts are also a matter of location, if the city with its built structures and concentration of population is located in the northern or southern part of this basin, or more inland or directly at the coast. As there are many different definitions in use trying to determine what a city is, also in the different national contexts of the bsr, here it is cities in the sense of being human-dominated densely populated areas, which are also characterized by higher concentrations of built-up areas, infrastructure, and soil-sealing as well as socioeconomic roles than rural settlements are. Those characteristics render cities also especially vulnerable to climate change impacts while there are some opportunities arising too. There are many studies on climate change impacts on the Baltic Sea itself as well as on the various ecosystems, but the studies on the observed as well as potential future impacts of climate change on cities are disperse, many are also of a national character or concentrating on a small number of cases, leaving some cities not well studied at all. This renders an all-encompassing picture on the cities within the bsr difficult and even more complicated as every city provides a mix of built-up and open structures, of socioeconomic structure and role in a region, nation-state, or even on an international level, and further characteristics. Their urban development is dependent on manifold various interdependencies as well as climatic and nonclimatic drivers, such as, to name just a few diverse examples, urban to international governance processes, or topography and location, or also different socioeconomic vulnerabilities within the Baltic Sea basin. Accordingly every urban society and structure provides specific exposure, vulnerabilities, and adaptive capacity. Generally, the cities of the bsr have to deal with the impacts of temperature rise, natural hazards, and extreme events, and, depending on location and topography, with sea-level rise. With reference to temperature rise and the increase of heat waves, it is important to consider that cities of a certain size within the Baltic Sea basin contribute to their own urban climatic conditions and provide already urban heat islands. Also, urban planning and building facilitated by local political decisions contribute to the extent of urban floods as well as their damage, as these are regulating, for example, the sealing of soils or new built-up areas in flood-prone zones.


Ecosystem Services and Human Health  

Elisabet Lindgren and Thomas Elmqvist

Ecosystem services refer to benefits for human societies and well-being obtained from ecosystems. Research on health effects of ecosystem services have until recently mostly focused on beneficial effects on physical and mental health from spending time in nature or having access to urban green space. However, nearly all of the different ecosystem services may have impacts on health, either directly or indirectly. Ecosystem services can be divided into provisioning services that provide food and water; regulating services that provide, for example, clean air, moderate extreme events, and regulate the local climate; supporting services that help maintain biodiversity and infectious disease control; and cultural services. With a rapidly growing global population, the demand for food and water will increase. Knowledge about ecosystems will provide opportunities for sustainable agriculture production in both terrestrial and marine environments. Diarrheal diseases and associated childhood deaths are strongly linked to poor water quality, sanitation, and hygiene. Even though improvements are being made, nearly 750 million people still lack access to reliable water sources. Ecosystems such as forests, wetlands, and lakes capture, filter, and store water used for drinking, irrigation, and other human purposes. Wetlands also store and treat solid waste and wastewater, and such ecosystem services could become of increasing use for sustainable development. Ecosystems contribute to local climate regulation and are of importance for climate change mitigation and adaptation. Coastal ecosystems, such as mangrove and coral reefs, act as natural barriers against storm surges and flooding. Flooding is associated with increased risk of deaths, epidemic outbreaks, and negative health impacts from destroyed infrastructure. Vegetation reduces the risk of flooding, also in cities, by increasing permeability and reducing surface runoff following precipitation events. The urban heat island effect will increase city-center temperatures during heatwaves. The elderly, people with chronic cardiovascular and respiratory diseases, and outdoor workers in cities where temperatures soar during heatwaves are in particular vulnerable to heat. Vegetation and especially trees help in different ways to reduce temperatures by shading and evapotranspiration. Air pollution increases the mortality and morbidity risks during heatwaves. Vegetation has been shown also to contribute to improved air quality by, depending on plant species, filtering out gases and airborne particulates. Greenery also has a noise-reducing effect, thereby decreasing noise-related illnesses and annoyances. Biological control uses the knowledge of ecosystems and biodiversity to help control human and animal diseases. Natural surroundings and urban parks and gardens have direct beneficial effects on people’s physical and mental health and well-being. Increased physical activities have well-known health benefits. Spending time in natural environments has also been linked to aesthetic benefits, life enrichments, social cohesion, and spiritual experience. Even living close to or with a view of nature has been shown to reduce stress and increase a sense of well-being.


The Emerging Environmental Economic Implications of the Urban Water–Energy–Food (WEF) Nexus: Water Reclamation with Resource Recovery in China, India, and Europe  

Daphne Gondhalekar, Hong-Ying Hu, Zhuo Chen, Shresth Tayal, Maksud Bekchanov, Johannes Sauer, Maria Vrachioli, Mohammed Al-Azzawi, Hannah Patalong, Hans-Dietrich Uhl, Martin Grambow, and Jörg E. Drewes

With economic and population growth, industrialization, urbanization, and globalization, demand for natural resources such as water, energy, and food continues to increase, particularly in cities. Overconsumption of resources has led to degradation of the environment, a process that is interacting with and is further accelerated by a dangerous alteration to the climate. Fast growing cities worldwide already face severe technical difficulties in providing adequate infrastructure and basic services in terms of water and energy. This situation is set to become increasingly difficult with climate change impacts. The latter are increasingly affecting economically developing as well as developed countries. However, cities often have limited capacities to take comprehensive climate action. Hence, practicable, scalable, and adaptable solutions that can systematically target key entry points in cities are needed. The Water-Energy-Food (WEF) Nexus concept is one potential integrated urban planning approach offering cities a more sustainable development pathway. Within this concept, urban water reclamation with resource recovery offers a key potential: reclaimed products such as water, bioenergy, nutrients, and others are valuable resources for which markets are emerging. Reclaiming water can also reduce stress on natural resources and support the prevention of environmental pollution. Thus, it can support water, energy, and food security and the achievement of the United Nations Sustainable Development Goals. However, so far there are few implemented examples of urban water reclamation with resource recovery at urban scales. Examples of good practice in cities in China, India, and Europe highlight key enablers and barriers to the operationalization of water reclamation with resource recovery and implications in terms of environmental economics relevant for cities worldwide. These findings can support a systemic sociotechnical transition to a circular economy.


Early African Pasts: Sources, Interpretations, and Meanings  

David Schoenbrun

Writing Africa’s history before the 10th century almost always means relying on sources other than written documents, which increase in number especially from the 16th century onward. Archaeology (including the study of art objects), the comparative study of historically related languages, paleo-environmental studies, and oral traditions provide the bulk of information. Writing Africa’s early history ideally involves collaboration among experts in using each kind of source, an increasingly common practice. Despite the challenges of analysis and interpretation posed by this base of sources, early African history has a depth and breadth akin to the histories made from the written sources in archives. Even so, whereas written documents provide details about individuals and precise dates, the sources for writing early African histories more often provide detail about conceptualization, for example, of time, hospitality, and individualism and about larger, environmental contexts shaping those concepts and shaped by the actions of the people who held them. Translating such concepts and scales of action into accounts accessible to those—including many historians—not steeped in the methodological conventions underlying the analysis of each source is a major challenge facing historians of Africa’s earlier past.


Ecological Water Management in Cities  

Timothy Beatley

Managing water in cities presents a series of intersecting challenges. Rapid urbanization, wasteful consumption, minimal efforts at urban or ecological planning, and especially climate change have made management of urban water more difficult. Urban water management is multifaceted and interconnected: cities must at once address problems of too much water (i.e., more frequent and extreme weather events, increased riverine and coastal flooding, and rising sea levels), but also not enough water (e.g., drought and water scarcity), as well as the need to protect the quality of water and water bodies. This article presents a comprehensive and holistic picture of water planning challenges facing cities, and the historical approaches and newer methods embraced by cities with special attention to the need to consider the special effects of climate change on these multiple aspects of water and the role of ecological planning and design in responding to them. Ecological planning represents the best and most effective approach to urban water management, and ecological planning approaches hold the most promise for achieving the best overall outcomes in cities when taking into account multiple benefits (e.g., minimizing natural hazards, securing a sustainable water supply) as well as the need to protect and restore the natural environment. There are many opportunities to build on to the history of ecological planning, and ecological planning for water is growing in importance and momentum. Ecological planning for water provides the chance to profoundly rethink and readjust mankind’s relationship to water and provides the chance also to reimagine and reshape cities of the 21st century.


Water and Economy-Wide Modeling: An Overview  

William D. A. Bryant

General equilibrium theory thinks of the economy as a collection of interconnected markets, each of which, in isolation and in combination, is driven toward some sort of equilibrium. Computable general equilibrium (CGE) models add to this abstract point of view by calibrating models of the economy using actual economic data. The aim is to empirically solve for equilibrium demand, supply, and price levels across the markets in the economy. Many areas of economic analysis, reform, and policymaking have benefitted from scrutiny in a CGE context. This is particularly true of issues to do with tax and tariff reform, where CGE models first gained prominence. More recently, the areas of environmental economics and regulation has attracted the attention of CGE modelers. Considerations of environment and environmental regulation, inevitably involve a consideration of issues to do with water. Such issues range from aquaculture through pricing of water to virtual water—and many points in between. In the analysis of each of these issues—and the role water plays in the overall economy, CGE models have made an important contribution to understanding and informed policymaking.