Climate change is imposing complex, interacting effects on every ecosystem around the world, and of course, there is more change to come. Problems associated with heat stress, food availability, energy security, air quality, water quality and availability, flooding, and sea level rise affect even the most remote areas, but these issues are amplified in urban areas [Grimm et al., 2008], where many people already disproportionately experience disparities in health and economic and political equity [Tessum et al., 2019].
Continuing rapid urban development will only intensify these disparities unless measures are taken to ameliorate them. At the same time, cities face additional stresses from ongoing and projected climate change [U.S. Global Change Research Program, 2017]. Under a high-emissions scenario called RCP 8.5 (Representative Concentration Pathway 8.5), a combination of sea level rise and the increasing intensity and frequency of extreme weather may make many cities nearly uninhabitable by the end of this century.
Recent unprecedented losses in equity, health, and life have exposed gaps in our readiness to cope with climate-related extremes today and our unpreparedness to face them in the future. Thus, there is a pressing need for convergent research that investigates paths toward urban sustainability. Many cities, including Barcelona, Chicago, New York, Paris, and Seattle, are attempting to increase sustainability through climate action plans that map out steps to reduce emissions.
However, there is a need for research that feeds into these plans to further connect sustainability science more fully with efforts to address equity and justice issues and with the many sectors—such as infrastructure, energy, and transportation—comprising the urban environs. Such efforts should aim to design multidisciplinary and multistakeholder networks that can collectively coproduce knowledge and information to deliver actionable research-based solutions and informed decision-making to the problems that communities of many sizes face (Figure 1). We now have a time-sensitive opportunity to achieve such a vision for the coproduction of knowledge, forming public-private-community partnerships with the purpose of attaining the United Nations 2030 Agenda for Sustainable Development.
Interacting Systems, Unintended Consequences
Considerable efforts have been invested in devising infrastructure-based schemes for climate adaptation and advancing urban sustainability [Rosenzweig et al., 2009; Sharma et al., 2016; Zhao, 2018]. However, sustainability-related strategies and actions must be carefully orchestrated because their effectiveness depends on combinations of social, economic, health, and climate conditions.
Strategies can also have complex socioecological trade-offs [Cao et al., 2016; Sharma et al., 2018] and may trigger unintended climatic and socioeconomic consequences [Zhao et al., 2017]. For example, models indicate that large-scale implementation of cool roofs designed to reflect more sunlight than conventional roofs may reduce precipitation in urban areas [Georgescu et al., 2014], potentially exacerbating water stress. Green infrastructure, which relies on plants to manage water runoff and filter and cool the air, may require irrigation and should be sited carefully. In dry-climate cities where water is already scarce—and becomes scarcer in the projected future under climate change [Zhao et al., 2017]—green infrastructure’s interaction with and effects on climate change are poorly understood.
Traditionally, urban planning concentrated on top-down interventions by agencies within municipal governments. However, in recent decades, there has been a push to create more interdisciplinary knowledge that considers a broader range of potential impacts. As part of this push, a recent influx of “smart city” approaches views cities as mechanistic systems composed of discrete components to be optimized individually. However, cities cannot achieve sustainability without a holistic view of the interdependencies among essential human needs (food, energy, and water); constructed urban infrastructure; associated natural systems (air, water, land, ecosystems); and social, political, and legal decisions spanning all relevant scales (individuals, neighborhoods, municipalities, regions, nations). For example, national policy can limit or enhance what is doable within a city. At the local scale, residents of a single neighborhood can delay projects by tying them up in litigation. Inadequate consideration of these interdependencies can thus result in unintended social stresses, especially for the poor.
Urban metabolisms, which consider the flows of materials and energy within a city and which comprise subsystems related to food, energy, and water, are a concept that takes such a holistic view. These subsystems and their associated climate challenges have been studied for several decades, but relationships among subsystems are often obscured by the discipline-bound approach of past research. We see the urban metabolism framework as being an essential conceptual and quantitative model for studying the complex interactions among people, constructed infrastructure, and surrounding natural systems in cities of all sizes.
Generally, urban sustainability research is focused on very large urban systems. However, billions of people live in smaller communities, and although cities of varying sizes face many of the same problems amid climate change, a single solution for a given problem is unlikely to fit for all. Instead, cities require sustainability solutions involving infrastructure, technology, policy, and management that are tailored to their own vulnerable systems. This inclusiveness in research and planning will help improve the lives of people in less densely populated areas that are often neglected in conversations about sustainability.
Understanding the impacts of urban systems on the environment at local to global scales also requires considering complex and interdependent social and physical factors, which can be studied using increasingly sophisticated models. Despite advances in computing, however, many knowledge gaps still exist. These gaps involve both spatial and temporal scales, the need for improved data sets about urban land use, and the need for better and more detailed measurements of complex urban flows (e.g., meteorology, air quality, combined sewage outflows, mobility). These gaps prevent adequate estimates of the flows of energy and matter in urban systems [Sharma et al., 2020]. More investments in focused scientific and engineering research could provide needed perspective on urban woes and potential solutions across scales.
Needed: Multidisciplinary, Multistakeholder Research
Contemporary urban sustainability research requires a broad multidisciplinary methodology. Yet such research is challenging and therefore understandably uncommon. Engineers, social scientists, ecologists, and experts in the arts and humanities speak different disciplinary languages and approach the analysis of data from urban environments in different ways [Jacobs, 2014]. Their models, data sets, and findings are not easily coupled and integrated, meaning potentially valuable urban tools and insights remain undeveloped.
However, system-level solutions can be better designed and produce fewer unintended consequences if we explore issues that lie at the intersections and boundaries of the natural sciences, engineering, humanities, social sciences, arts, and other disciplines. Such a holistic approach might have, for example, alerted Los Angeles city planners to the distressingly high costs to building owners associated with a 2013 law requiring that all buildings install cool roofs.
More specifically, the arts, humanities, and social sciences offer important pathways to and lessons for understanding urban sustainability that complement those typically followed by the natural science and engineering fields [Pykett et al., 2020]. For example, community-based and participatory research methods can identify climate-related infrastructure, equity, and health risks associated with food, energy, and water needs. These methods can also help project future problems for residents of small and poor communities that are generally not represented in municipal decision-making.
Making science more relatable to the public may lead to more community involvement in planning for futures that consider local histories. In many cities, public history, heritage studies, and museum studies contribute to sustainability research through their connections with local people, past and present.
Communicating in ways that can overcome science and engineering language barriers and that use culturally meaningful framing is useful in relating traditions and lifestyles to current and future sustainability challenges in communities. Such approaches can focus on community priorities and concerns shared through cultural traditions in art, poetry, storytelling, music, or culinary arts and on using history to teach lessons about how people cause or adapt to environmental changes.
Each of these pathways can be vital in engaging policy makers, voters, and other community members in responding to environmental threats and participating in urban sustainability solutions. They can also lead to important insights into urban systems over a wide range of geographical and temporal scales (daily, seasonal, and long term), from the neighborhood to the metropolis and beyond.
Multidisciplinary approaches also support deep, bidirectional engagement with community stakeholders that leads to improved understanding of stakeholder concerns and priorities and to collaborations with players critical to delivering solutions. Communities of different sizes require different solutions depending on their resources, capabilities, and priorities.
Community groups and municipal leaders have direct understanding of pressing local problems and of the municipal settings in which solutions must be implemented. Individuals and enterprises in business, especially those that combine social, cultural, and environmental issues, referred to as social entrepreneurship, are also key to the success of sustainability solutions. Beyond providing insight into finance and feasibility issues, they can help drive the design, development, and delivery of scalable solutions. Moreover, nongovernmental organizations often have extensive experience working with multiple stakeholders to effect environmental change, albeit sometimes with a limited focus on urban sustainability that lacks a convergent multidimensional approach.
Toward Convergent Urban Sustainability Sciences
Knowledge gaps in convergent urban sustainability research can be narrowed by focusing on cities as complex, multiscale, interdependent, and adaptive systems with active interactions among social, natural, and engineered systems. Such an approach should include local stakeholders, businesses, and communities. Toward this end, we propose a strategy for constructing urban research networks for convergent urban sustainability science that are equally relevant for cities of all sizes (Figure 2).
Now is the time for collaborations and partnerships spanning research disciplines, the private and nonprofit sectors, and representatives from municipalities to define holistic pathways forward to tackle critical urban sustainability challenges facing cities of all sizes. Interactive planning and decision-making processes already exist, but they require additional multidiscipline and cross-discipline interactions to be fully successful.
Investments in multidisciplinary and multistakeholder convergent research can guide urban innovations and advance sustainability on multiple fronts, both locally and globally. Together we can close the gaps between the diagnosis of climate-related urban challenges and the identification and implementation of appropriate solutions and partnerships that account for community concerns about health and equity and that are needed to ensure more sustainable food, energy, and water futures for our cities.
This article is an outcome of the 2019 CURES Connections Workshop: New Voices and Paths to Urban Sustainability, supported by National Science Foundation grant 1929856 to explore the concepts for advancing sustainable urban systems research networks. We thank 125+ diverse workshop participants. We especially acknowledge the contributions of Anne-Marie Hanson of the University of Illinois at Springfield and Elizabeth Kocs, Cynthia Klein-Banai, Dean Massey, and Moira Zellner of the University of Illinois at Chicago.