3.1. Accelerate urban sustainability transformations

Proximity of actors and resources in the urban context makes cities ideal loci for testing and realizing accelerated transitions (Frantzeskaki et al., Reference Frantzeskaki, McPhearson and Kabisch2021). Despite the many innovative practices and experiments at city level, transitions toward sustainability are at best slow and not at the scale that is required. Traditional scientific approaches to knowledge generation typically operate over long timeframes that are not geared to the urgent responses needed to address current global urban challenges. An acceleration of policy and planning responses to global sustainability challenges is thus needed, with due consideration not to leave already marginalized populations behind, exacerbating existing inequalities or creating new ones (Gupta et al., Reference Gupta, Bai, Liverman, Rockström, Qin, Stewart-Koster, Rocha, Jacobson, Abrams, Andersen, McKay, Bala, Bunn, Ciobanu, DeClerck, Ebi, Gifford, Gordon, Hasan and Gentile2024).

There is ample evidence that natural systems change in a non-linear manner with tipping points (Armstrong Mckay et al., Reference Armstrong Mckay, Staal, Abrams, Winkelmann, Sakschewski, Loriani, Fetzer, Cornell, Rockström and Lenton2022), but the level and pace of actions are lagging. Delaying actions fuel the urgency to act as the window of opportunity starts to close. In climate, for example, an increased urgency to take climate action is represented in cities’ agendas, with many cities declaring a climate emergency (Salvia et al., Reference Salvia, Reckien, Geneletti, Pietrapertosa, D'Alonzo, De Gregorio Hurtado, Chatterjee, Bai and Ürge-Vorsatz2023). These cities prepare daring plans and proposals to be put in action such as implementing nature-based solutions and mobilizing social movements (e.g., coastal retreat from at risk coastal settlements in Staten Island, New York as part of a wider planned relocation effort or transforming historic urban parks in Copenhagen into stormwater capture to reduce risks from urban flooding). These seeds of transformation in cities are signs of hope (Loorbach et al., Reference Loorbach, Wittmayer, Avelino, von Wirth and Frantzeskaki2020) but their emergence and resulting implementation remain regionally uneven: While those cities with sufficient governance, resources, and knowledge capacities take advantage of these seeds of transformation to trigger and scale transformative agendas (Pereira et al., Reference Pereira, Frantzeskaki, Hebinck, Charli-Joseph, Drimie, Dyer, Eakin, Galafassi, Karpouzoglou, Marshall, Moore, Olsson, Siqueiros-García, van Zwanenberg and Vervoort2020), the rest of the cities worldwide lag behind.

Research shows many solutions (e.g., increasing self-sufficiency or choosing building materials with lower net emissions) are already available and that they have already proven to be effective in dealing with climate change (Lin et al., Reference Lin, Ossola, Alberti, Andersson, Bai, Dobbs, Elmqvist, Evans, Frantzeskaki, Fuller, Gaston, Haase, Jim, Konijnendijk, Nagendra, Niemelä, McPhearson, Moomaw, Parnell and Tan2021). Therefore, the challenge is how to accelerate their uptake and eventual mainstreaming. While several frontrunner cities and businesses are taking actions to address climate, biodiversity, and resource challenges by setting science-based targets, many more need to follow urgently (Bai et al., Reference Bai, Bjørn, Kılkış, Sabag Muñoz, Whiteman, Hoff, Seaby Andersen and Rockström2022). Yet, often existing policy and planning efforts are not capable of supporting immediate and fast-paced actions. In addition, even if strong sustainability goal-driven governance is possible, many challenges remain in identifying and navigating tradeoffs between different goals and targets. A proactive approach to accelerating transitions is also essential to reduce the need for reactive quick fixes that are less effective and often result in maladaptation.

Historical research on socio-technological systems and how they transform revealed that novelty—in the form of new practices, technologies, or institutions—is key to achieving transition (Loorbach et al., Reference Loorbach, Frantzeskaki and Avelino2017). Many of our infrastructure systems have undergone such pathways of transformation, e.g., shifting from decentralized wastewater systems to centralized ones, or more recently, transitions toward renewable energy systems that become more prominent in the energy mix and facilitate the creation of self-organized energy communities (Wittmayer et al., Reference Wittmayer, de Geus, Pel, Avelino, Hielscher, Hoppe, Mühlemeier, Stasik, Oxenaar, Rogge, Visser, Marín-González, Ooms, Buitelaar, Foulds, Petrick, Klarwein, Krupnik, de Vries and Härtwig2020). Contemporary transformations however seem to be more complex. Multiple forms of innovations reconfigure current ways of organizing and practicing: governance and financial innovations such as crowdfunding, participatory budgeting, and citizen councils, innovations in knowledge production and sharing such as citizen science and digital platforms, societal innovations such as time banking and slow food movements, and technological advances in, for example, artificial intelligence. These innovations and advances across a diversity of arenas—bio-regional, socio-economic, and governance contexts—offer opportunities for transformative changes to tackle multiple sustainability issues while also presenting new regulatory challenges. In addition, the vastly different trajectories of urbanization being experienced in the rapidly urbanizing global South opened the space for innovations in technical solutions, partnership models, financing mechanisms, and service delivery strategies that may be applicable at different levels in different contexts (Nagendra et al., Reference Nagendra, Bai, Brondizio and Lwasa2018). Shared visions and goals for a desirable future, while recognizing various underlying values and world views is a critical step in identifying implementation pathways and transformative solutions (Bai, van der Leeuw, et al., Reference Bai, van der Leeuw, O'Brien, Berkhout, Biermann, Brondizio, Cudennec, Dearing, Duraiappah, Glaser, Revkin, Steffen and Syvitski2016; McPhearson, Iwaniec, et al., Reference McPhearson, Iwaniec and Bai2016).

In this context, there are four promising new concepts or recent developments that can inform an accelerated transformation to more sustainable futures:

1. i) Social tipping: Social tipping research focuses on the potential of certain social changes to bring about large scale system change through self-reinforcing processes. Theoretical frameworks are proposed to understand how various actors, enabling factors and mechanisms can trigger such cascading effects (Farmer et al., Reference Farmer, Hepburn, Ives, Hale, Wetzer, Mealy, Rafaty, Srivastav and Way2019; Otto et al., Reference Otto, Donges, Cremades, Bhowmik, Hewitt, Lucht, Rockström, Allerberger, McCaffrey, Doe, Lenferna, Morán, van Vuuren and Schellnhuber2020; Winkelmann et al., Reference Winkelmann, Donges, Smith, Milkoreit, Eder, Heitzig, Katsanidou, Wiedermann, Wunderling and Lenton2022). Bai (Reference Bai2024) proposed a method to identify anticipated tipping points via peer effect, using EV adoption in Shanghai as a case study. Still, while identifying a tipping point retrospectively is relatively easy, doing so before the tipping occurs remains a challenge.

2. ii) Nexus approach across domains: By focusing on multiple domains, a nexus approach aims to harness synergies and avoid tradeoffs, thereby has the potential to accelerate transformation. The water-energy-food nexus is perhaps the most studied nexus (Chan, Reference Chan2015; Newell, Reference Newell2020). More recently, a climate change-biodiversity-society nexus proposed by the IPBES and IPCC Joint Workshop in 2020 (Pascual et al., Reference Pascual, McElwee, Diamond, Ngo, Bai, Cheung, Lim, Steiner, Agard, Donatti, Duarte, Leemans, Managi, Pires, Reyes-García, Trisos, Scholes and Pörtner2022; Pörtner et al., Reference Pörtner, Scholes, Agard, Archer, Arneth, Bai, Barnes, Burrows, Chan, Cheung, Diamond, Donatti, Duarte, Eisenhauer, Foden, Gasalla, Handa, Hickler, Hoegh-Guldberg and Ngo2021), the IPBES report on Transformative Change Assessment (O'Brien et al., Reference O'Brien, Garibaldi and Agrawal2024), and IPBES NEXUS Assessment across biodiversity, water, food and health (McElwee et al., Reference McElwee, Harrison, van Huysen, Alonso Roldán, Barrios, Dasgupta, DeClerck, Harmáčková, Hayman, Herrero, Kumar, Ley, Mangalagiu, McFarlane, Paukert, Pengue, Prist, Ricketts, Rounsevell and Obura2024), started to receive much attention.

3. iii) Collaboration across cities and actors: There is a strong case for cities to be altruistic, as doing so not only benefits recipients but also themselves (Bai, Reference Bai2024). In addition, more and stronger collaborations across actors must be explored to achieve rapid and large scale transformation (Oke et al., Reference Oke, Bekessy, Frantzeskaki, Bush, Fitzsimons, Garrard, Grenfell, Harrison, Hartigan, Callow, Cotter and Gawler2021). For example, as two key subnational actors in sustainability, a stronger collaboration across cities and businesses is essential for living within the safe and just Earth system boundaries. There is untapped climate mitigation potential in stronger city–business collaborations, especially when ambitious targets can be aligned among co-located cities and companies such as for electrification of transportation and district heating/cooling (Kılkış, Bjørn, et al., Reference Kılkış, Bjørn, Bai, Liu, Whiteman, Crona, Andersen, Hasan, Vijay and Sabag2024).

4. iv) Linking cities to planetary targets: Mobilizing cities and businesses to set ambitious targets is essential to achieve global level goals, such as staying within the planetary or safe and just Earth system boundaries (Bai et al., Reference Bai, Bjørn, Kılkış, Sabag Muñoz, Whiteman, Hoff, Seaby Andersen and Rockström2022; Rockström et al., Reference Rockström, Gupta, Qin, Lade, Abrams, Andersen, Armstrong Mckay, Bai, Bala, Bunn, Ciobanu, DeClerck, Ebi, Gifford, Gordon, Hasan, Kanie, Lenton, Loriani and Zhang2023). Cross-scale translation of planetary or Earth system boundaries and subsequent science-based target setting can ensure the grand sum of targets and actions conducted by all actors remain within the designated boundaries (Bai, Reference Bai2024; Bai et al., Reference Bai, Bjørn, Kılkış, Sabag Muñoz, Whiteman, Hoff, Seaby Andersen and Rockström2022; Bjørn et al., Reference Bjørn, Lloyd and Matthews2021; SBTN, 2020).

To advance research to accelerate urban sustainability transformations, we identify six guiding research questions as in Table 1. See Supplementary Material S2 for the full list of 29 research questions.

Table 1.

Guiding research questions and ranking for “accelerate urban sustainability transformations”

3.2. Ensure equity and inclusivity

Ensuring equity while enhancing sustainability are intertwined dual challenges for cities, both in response to existing issues and for future planning. Cities concentrate socio-economic opportunities but also often generate pronounced inequalities that can reduce human wellbeing. In the context of rapid urban population growth, ensuring equity and inclusivity while achieving greater resource efficiency and lower ecological footprint is a critical task for political leaders, policy makers, practitioners and communities. There have been strong calls globally for justice to be a core dimension of urban sustainability transitions. The first five Sustainable Development Goals (UNGA, 2015), poverty reduction, food security, health, education, and gender equality are all primary equity outcomes from sustainable urbanization, supported by further SDGs, such as water, energy, work, infrastructure, climate action, and sustainable cities. Beyond the SDGs an array of policy frameworks, such as the IPCC AR6 climate report, the UN New Urban Agenda or the World Bank Sustainable Cities Framework Program 4, articulate clear ambitions for greater urban inclusion. Such frameworks are complemented by civil society movements emphasizing “the right to the city” (Harvey, Reference Harvey2003), or notions of justice such as environmental justice, the “just city” (Fainstein, Reference Fainstein2014), “housing justice” (Roy et al., Reference Roy, Rolnik, Graziani and Malson2020) or decolonial “dwelling justice” (Porter & Kelly, Reference Porter and Kelly2022), and more recently climate justice (Bustamante et al., Reference Bustamante, Roy, Ospina, Achakulwisut, Aggarwal, Bastos, Broadgate, Canadell, Carr, Chen, Cleugh, Ebi, Edwards, Farbotko, Fernández-Martínez, Frölicher, Fuss, Geden, Gruber and Zscheischler2023). However, many critical research questions await answers.

The Sustainable Development Goals aim to “end poverty in all its forms everywhere” as the number one global challenge by 2030. Cities typically offer more economic opportunities than rural areas (Young, Reference Young2013), due to broader and deeper labor markets with complex exchange networks, including greater gender inclusivity (Evans, Reference Evans2019). However, cities are also sites of labor exploitation that often exhibit inequalities in the distribution of income and wealth disparities influenced by social stratification. Because cities concentrate wealth, urban inequality tends to increase with city size (Castells-Quintana et al., Reference Castells-Quintana, Royuela and Veneri2020). Given ongoing urbanization, urgent research is needed on urban economic inequality (e.g., poverty and class inequalities), its drivers, and solutions. This includes direct urban poverty alleviation through employment as well as indirect channels such as access to education (Nasir et al., Reference Nasir, Alam and Fatima2020), mobility services (Farré et al., Reference Farré, Jofre-Monseney and Torrecillas2020), commuting structures (T. Li et al., Reference Li, Dodson and Goldie2021), infrastructure (including digital infrastructure (Macaya et al., Reference Macaya, Ben Dhaou and Cunha2021), and inclusive urban governance. Further research is needed on gender disparities in entrepreneurship and participation (Tripathi, Reference Tripathi2023). Emerging programs that focus on cities through a degrowth perspective (Kaika et al., Reference Kaika, Varvarousis, Demaria and March2023) must attend to the implications of urban inequality. Likewise, urban strategies to reduce environmental demand and mitigate climate change must address class-based inequities (Huber, Reference Huber2023).

Equality in available urban services, such as housing, health, education, transportation and amenity has long been part of the discourse and practice in urban planning. Environmental justice is becoming central to urban sustainability and is central to equity incorporating also accessibility concerns of available infrastructure services and benefits. It recognizes the adverse distributional consequences of urban environmental externalities, such as toxic wastes, pollutants, and environmental hazards, within the context of wider movements for social justice (Collins, Reference Collins, Manfredo, Vaske, Rechkemmer and Duke2014). New iterations of this research program in the US have deployed racial and decolonial perspectives on climate justice (Fitz-Henry, Reference Fitz-Henry2022). Subsequent analysis has broadened the environmental justice frame to address climate impact disparities (Mitchell & Chakraborty, Reference Mitchell and Chakraborty2018), within adaptation justice, and within wider systemic approaches to human-environment systems (Henrique & Tschakert, Reference Henrique and Tschakert2021).

Recent decades have seen growing recognition of urban social justice gaps across various demographic groups. An array of novel theoretical and conceptual approaches has been developed to understand distributive justice, procedural justice, and the need to recognize systemic and structural vulnerabilities, incorporating local, traditional, and indigenous knowledge. Such perspectives examine how socio-demographics, land-markets and institutions shape residents’ experiences of urban land use, service access, and climate vulnerability. Distributional inequality can result from formal planning or unintended gentrification. Historically, land use in some cities has segregated minorities, exposed poorer communities to flooding, and sited toxic or offensive land-uses in disadvantaged areas. The latter is related to the accumulation of the wealthy in areas where the availability and the delivery of urban services, such as green spaces, education, health, and transportation, are improved, whilst leading to soaring land prices and the displacement of the poor. The lack of participation, or policy co-design, from impacted communities and/or ineffective participation exacerbates urban inequality.

Inequities in access to environmental resources, such as water and energy, as well as to various ecosystem services in cities, have already been considered at length in the literature (Shih, Reference Shih2022). More recently, such inequities are increasingly studied in the context of climate change. Importantly, In the context of climate justice, in addition to pre-existing injustices (Collins, Reference Collins, Manfredo, Vaske, Rechkemmer and Duke2014), new inequalities may emerge from lack of adaptation justice (Bustamante et al., Reference Bustamante, Roy, Ospina, Achakulwisut, Aggarwal, Bastos, Broadgate, Canadell, Carr, Chen, Cleugh, Ebi, Edwards, Farbotko, Fernández-Martínez, Frölicher, Fuss, Geden, Gruber and Zscheischler2023). For example, cities increasingly use nature-based solutions as low-cost investments or insurance to build resilience to climate change (Frantzeskaki et al., Reference Frantzeskaki, McPhearson, Collier, Kendal, Bulkeley, Dumitru, Walsh, Noble, van Wyk, Ordóñez, Oke and Pintér2019; Hahn et al., Reference Hahn, Sioen, Gasparatos, Elmqvist, Brondizio, Gómez-baggethun, Folke, Setiawati, Atmaja, Arini, Jarzebski, Fukushi and Takeuchi2023; McPhearson et al., Reference McPhearson, Frantzeskaki, Ossola, Diep, Anderson, Blatch, Collier, Cook, Culwick Fatti, Grabowski, Grimm, Haase, Herreros-Cantis, Kavonic, Lin, Lopez Meneses, Matsler, Moglia, Morató and Zhou2025, Reference McPhearson, Kabisch and Frantzeskaki2023), e.g., runoff abatement and heat mitigation in cities. However, implementation of these often prioritizes the protection/benefits of affluent areas and leads to displacement of the poor. This phenomenon is called “green climate gentrification” (Anguelovski et al., Reference Anguelovski, Connolly, Pearsall, Shokry, Checker, Maantay, Gould, Lewis, Maroko and Roberts2019) and should be regarded as a form of maladaptation. Given the manifold transformations occurring through global environmental change, including via climate change vectors but also resource degradation and exhaustion there is a critical necessity to better understand factors behind urban inequalities and the mechanisms to alleviate them, whether conventional or radical (T., M. McPhearson et al., Reference McPhearson, Raymond, Gulsrud, Albert, Coles, Fagerholm, Nagatsu, Olafsson, Soininen and Vierikko2021).

Ensuring access to water and sanitation for all is linked to multiple dimensions of equity; however, progress remains limited with 2 billion people still expected to live without access to safely managed drinking water in 2030 (UN, 2024), especially in rapidly growing cities where growth exceeds infrastructure development. These disparities in service delivery hinder inclusive water, sanitation, and hygiene planning (Luwe et al., Reference Luwe, Sindall, Garcia-Becerra, Chinyama, Lohiya, Hope, Paczkowski, Komakech and Morse2022; Robinson et al., Reference Robinson, Barrington, Evans, Hutchings and Narayanaswamy2024). These services are also plagued by chronic inequities, particularly in historically colonized areas (Lue et al., Reference Lue, Bah, Grant, Lee, Nzekele and Tidwell2023), leading to public and political disengagement, worsening procedural inequities (Rodina et al., Reference Rodina, Harris, Ziervogel and Wilson2024). Inadequate low-quality, unsafe, and poorly maintained public facilities in poorer communities heighten health risks, especially during floods, heavy rain, and heat waves (Anthonj et al., Reference Anthonj, Mingoti Poague, Fleming and Stanglow2024). Women and girls are disproportionately impacted (Anthonj et al., Reference Anthonj, Mingoti Poague, Fleming and Stanglow2024) with cascading socio-economic effects (Robinson et al., Reference Robinson, Barrington, Evans, Hutchings and Narayanaswamy2024).

Housing is a key driver of urban inequality (Berry, Reference Berry2023) both through its direct impact on social reproduction and as a vehicle for financialized asset accumulation (Rolnik, Reference Rolnik2017). Spatial residential segregation can also restrict access to jobs, education, and services while increasing exposure to climate risks like floods, fires, and cyclones. Some examples provide lessons to mitigate NIMBY when implementing environmental infrastructure, such as the Hiroshima Naka Incineration Plant where parts of the plant are made public domain and noise is mitigated so that appreciation for and understanding of the infrastructure is increased (Asokan et al., Reference Asokan, Sioen and Kawazu2024). Socio-economically disadvantaged populations are often concentrated in areas with environmental degradation and inadequate infrastructure. Informal settlements often face heightened risks due to poor infrastructure, weak structural integrity, and proximity to hazards (French et al., Reference French, Trundle, Korte, Koto and de Graaf-van Dinther2021). Research must examine the processes driving informal housing and the governance and institutional pathways to achieve equitable policy solutions. Research is also required on viable institutional mechanisms for large-scale, regulated and sustainable social and affordable housing solutions. Processes of housing financialization and rentierism must be addressed through regulatory and governance reforms to protect both homeowners and tenants, especially from predatory financial instruments and actors. Finally, further research is needed on the environmental impact of housing, exploring degrowth (Kaika et al., Reference Kaika, Varvarousis, Demaria and March2023; Nelson et al., Reference Nelson, Schneider and Gauquelin2019) and circular economy (Horne et al., Reference Horne, Dorignon, Lawson, Easthope, Dühr, Moore, Baker, Dalton, Pawson, Fairbrother and Xiong2023), as well as the financial and carbon costs of new construction and rebuild versus reuse and retrofit (Ding & Ying, Reference Ding and Ying2019).

More recent post-human environmental justice perspectives highlight cities as habitats for diverse ecologies. Notions of ecological justice now include multi-species justice (Celermajer et al., Reference Celermajer, Schlosberg, Rickards, Stewart-Harawira, Thaler, Tschakert, Verlie and Winter2021; Pineda-Pinto et al., Reference Pineda-Pinto, Herreros-Cantis, McPhearson, Frantzeskaki, Wang and Zhou2021) and allied notions of “stewardship” (Mumaw & Mata, Reference Mumaw and Mata2022). These justice frameworks call for greater recognition of diverse values (Pascual et al., Reference Pascual, Balvanera, Anderson, Chaplin-Kramer, Christie, González-Jiménez, Martin, Raymond, Termansen, Vatn, Athayde, Baptiste, Barton, Jacobs, Kelemen, Kumar, Lazos, Mwampamba, Nakangu and Zent2023), including indigenous and non-conventional perspectives. Policy research is needed to address urban inequality and promote future justice.

To advance research to ensure equity and inclusivity, four guiding research questions emerge as given in Table 2. See Supplementary Material S2 for the full list of 26 research questions.

Table 2.

Guiding research questions and ranking for “ensure equity and inclusivity”

3.3. Amplify innovation from low and lower-middle income countries

Much of the future urbanization and associated challenges, opportunities, and innovation will occur in low and lower-middle income countries (LLMIC). This challenge should be placed at the core of urban scientific efforts. Centralized governance structures often hinder local transformations. Transitions in the urban North are facilitated in part by greater power and capacity by civil society. In contrast, many cities in the urban South are dependent on state capacity. Urban South already has rich urban knowledge, often derived from local experience and practice, in terms of empirical knowledge and frameworks on how to achieve sustainable growth along with social justice. LLMIC urban innovations offer valuable learning opportunities. However, the influential well-cited literature on urban sustainability still predominantly emanates from the urban North, for example on topics related to adaptation and mitigation in cities (Sharifi et al., Reference Sharifi, Jin and Aboagye2025), limiting the integration of LLMIC grassroots innovations into policy. Knowledge transfer should move beyond North-South linkages to include interactions between South-South and South-North, indigenous, and community-based approaches (Nagendra et al., Reference Nagendra, Bai, Brondizio and Lwasa2018). Recentering global urban sustainability science in LLMICs requires collaboration, capacity-building, and multi-directional knowledge exchange that recognizes, enhances, supports, and shares LLMICs scientific capacity.

Overall, research on innovation in urban regions of LLMICs has received less support and funding, yet their urban sustainability innovations span ecology, governance, and technology—often self-driven by active citizens (e.g., Sierra Leone's Freetown smartphone app that incentivizes tree planting and monitoring by urban residents to increase biodiversity and resilience and sustain livelihoods that depend on these green areas). Given the high population densities and deep inequities in cities of the global South, urban ecological restoration projects often fail to get off the ground, or remain top-down with little grassroots support (Wantzen et al., Reference Wantzen, Alves, Badiane, Bala, Blettler, Callisto, Cao, Kolb, Kondolf, Leite, Macedo, Mahdi, Neves, Peralta, Rotgé, Rueda-Delgado, Scharager, Serra-Llobet, Yengué and Zingraff-Hamed2019). Connecting ecological projects with culture and poverty alleviation improves community acceptance, as seen in restoration projects in riverine urban regions of Brazil (Hordones et al., Reference Hordones, Boëchat, Cunha, Brauns and Gücker2025) and communities contemplating relocation due to climate change in Fiji (Yoshida et al., Reference Yoshida, Sioen, Metuisela and Crichton2025). In cities where migration from rural regions to cities is high, participatory management and quality resettlement is important to be combined with conservation efforts. Integrating ecology and social justice supports lasting sustainability in LLMIC cities (Wantzen et al., Reference Wantzen, Alves, Badiane, Bala, Blettler, Callisto, Cao, Kolb, Kondolf, Leite, Macedo, Mahdi, Neves, Peralta, Rotgé, Rueda-Delgado, Scharager, Serra-Llobet, Yengué and Zingraff-Hamed2019). Formal institutional mechanisms for community engagement can result in innovative partnerships for the governance and management of urban blue-green infrastructure, creating enabling conditions that foster citizen stewardship of urban nature as found in the rejuvenation of urban lakes in Bangalore and in the urban forest restoration in Gurugram in India (Lele & Sengupta, Reference Lele and Sengupta2018; Pant, Reference Pant2018).

Innovative financing is crucial for urban revitalization. Often, governments can raise initial project funds through loans, grants, and co-financing but struggle with long-term funding. Latin America, China, and India use joint development and property taxes to sustain transit investments (Venter et al., Reference Venter, Mahendra and Hidalgo2019). Cities in LMMICs can innovate transit more freely, avoiding car-centric urban lock-in. For instance, in cities in Chile, where walking remains the predominant approach of transport especially for low-income communities, there has been an increase in community innovation in public design of streets to improve walking infrastructure (Herrmann-Lunecke et al., Reference Herrmann-Lunecke, Mora and Sagaris2020). Such innovations as those described above can be built on top of an infrastructure that already incorporates a high degree of walkability, without first reversing urban design intended for private automobiles.

Technological innovations have the capacity to enhance urban sustainability and wellbeing, but require local adaptation. Examples from COVID response in Kochi city in Kerala, India indicate that Smart Cities could leverage technology to achieve last mile connectivity only when they harnessed “people to people relationships” through Civil Society Organizations at ground level (Chakravarty & Mathew, Reference Chakravarty and Mathew2025). India's technology focused Smart City Mission (SMC) with its reliance on centralized Special Purpose Vehicles (SPVs) for management has been criticized for reducing public participation and exclusion of the poor, bypassing municipal processes and creating digital divides (Das, Reference Das2024). High density, youth demographics, and frugal innovation drive LLMIC urban sustainability, as seen in pandemic vaccine production (Reddy, Reference Reddy2022). As a result, Global South cities use technology innovatively but there is a need to supplement with local insights (e.g., related to safety and equity that may otherwise not be captured). In such cases, pairing databases with local perceptions helps to provide three-dimensional views of urban challenges. In Cape Town, NGOs combined GIS and community assessments to map sanitation safety issues for women. Such information could then be integrated, coded and provided to city officials to help them plan, as well as to community members to enable them to challenge ill-designed city plans with a sound foundation of good data (Borie et al., Reference Borie, Pelling, Ziervogel and Hyams2019).

A combination of innovations in approaches to LLMIC cities need tailored innovations in ecology, governance, and technology. Such challenges include aspects like high population densities, high migration, demographic distributions skewed to the young, and low overall incomes—however, these challenges can also become opportunities for innovation because of the creative mixing brought in by migrants, demographic dividend with high densities of young people, informal community organization and inexpensive resources—along with the opportunities provided by mobile internet and banking systems, and an informal environment that encourages local entrepreneurship (Andres et al., Reference Andres, Bakare, Bryson, Khaemba, Melgaço and Mwaniki2021; UN-Habitat, 2024). Unlike global North cities, cities in LMMIC countries are often not yet locked-in to unsustainable pathways of private car-oriented transport, or inefficient urban and building design, making it easier to design sustainable transit systems and green housing, for instance (UN-Habitat, 2024). Keeping local context, culture and principles of social justice in mind seem to be important for innovations to succeed in these regions over the long term.

In addition, in the realm of climate change, renewable energy is considered one of the strong mitigation measures, and at the same time, an area where technological innovation occurs. In the literature on renewable energy technologies and associated infrastructures (RET), not only the technological aspect but the social aspect has also been studied recently (Batel, Reference Batel2020; Ukoba et al., Reference Ukoba, Yoro, Eterigho-Ikelegbe, Ibegbulam and Jen2024). Researchers emphasize that social science has been very prolific in the last decades in publishing research that attempts to better understand the social acceptance of RET. It is highly possible that alongside cities in the global North, cities in LLMIC also face opposition to RET, not only in cities from the global North. It is equally important to carefully understand the social aspects such as the perceptions and beliefs of citizens and local communities in LLMICs while amplifying technological innovation.

To advance research to amplify innovation from LLMIC, six guiding research questions emerge as given in Table 3. See Supplementary Material S2 for the full list of 20 research questions.

Table 3.

Guiding research questions and ranking for “amplify innovation from LLMIC”

3.4. Negotiate complexity and systemic risks

Cities are human dominant, dynamic and evolving systems, demonstrating a high level of complexity and interdependencies (Bai, Surveyer, et al., Reference Bai, Surveyer, Elmqvist, Gatzweiler, Güneralp, Parnell, Prieur-Richard, Shrivastava, Siri, Stafford-Smith, Toussaint and Webb2016; Batty, Reference Batty2013; Chester et al., Reference Chester, Miller, Muñoz-Erickson, Helmrich, Iwaniec, McPhearson, Cook, Grimm and Markolf2023)). Complex systems also have emergent properties that can create additional sources of uncertainties (Liu et al., Reference Liu, Dietz, Carpenter, Alberti, Folke, Moran, Pell, Deadman, Kratz, Lubchenco, Ostrom, Ouyang, Provencher, Redman, Schneider and Taylor2007), making it difficult not only to understand how and why cities struggle to fix persistent and long standing problems, but also to innovate solutions that can be flexible enough to change over time as the complex nature of urban systems shift, morph, and evolve (Alberti et al., Reference Alberti, McPhearson, Gonzalez, Elmqvist, Bai, Frantzeskaki, Griffith, Maddox, McPhearson, Parnell, Romero-Lankao, Simon and Watkins2018). Such uncertainty can challenge planning, design, and management (Chester et al., Reference Chester, Miller, Muñoz-Erickson, Helmrich, Iwaniec, McPhearson, Cook, Grimm and Markolf2023; Güneralp & Seto, Reference Güneralp and Seto2008).

This complexity challenges current urban governance, planning, and management structures that, despite global diversity, tend to have similar traits suited for less complex systems. These approaches often address only subsystems such as transportation, energy supply, or climate resilience, when disturbances and extreme events (e.g., climate-driven) can impact multiple systems simultaneously or cascade between subsystems (Dodman et al., Reference Dodman, Hayward, Pelling, Castan Broto, Chow, Chu, Dawson, Khirfan, McPhearson, Prakash, Zheng and Ziervogel2022; Revi et al., Reference Revi, Roberts, Klaus, Bazaz, Krishnaswamy, Singh, Eichel, Poonacha Kodira, Schultz, Adelekan, Babiker, Bertoldi, Cartwright, Chow, Colenbrander, Creutzig, Dawson, De Coninck, De Kleijne and Ürge-Vorsatz2022). For example, when Hurricane Sandy hit the eastern seaboard of the United States in 2012, cities including New York City saw disruptions in communications, transportation, and energy systems, cascading to impact fuel, food, and water availability. When Hurricane Maria struck the island of Puerto Rico in 2017, multiple subsystem failures devastated residents, ecosystems, and infrastructure (Eakin et al., Reference Eakin, Muñoz-Erickson and Lemos2018).

Cities not only face internal uncertainties (Bai, van der Leeuw, et al., Reference Bai, van der Leeuw, O'Brien, Berkhout, Biermann, Brondizio, Cudennec, Dearing, Duraiappah, Glaser, Revkin, Steffen and Syvitski2016; McHale et al., Reference McHale, Pickett, Barbosa, Bunn, Cadenasso, Childers, Gartin, Hess, Iwaniec, McPhearson, Peterson, Poole, Rivers, Shutters and Zhou2015). Teleconnections and telecouplings across systems further challenge even the notion of cities as bounded systems because of how they expand the concept of urbanity (McHale et al., Reference McHale, Pickett, Barbosa, Bunn, Cadenasso, Childers, Gartin, Hess, Iwaniec, McPhearson, Peterson, Poole, Rivers, Shutters and Zhou2015) demonstrating increasingly tight connections across linked urban-rural systems (as seen during COVID-19, city dynamics are interconnected both globally and locally (McPhearson, Reference McPhearson, Hölscher and Frantzeskaki2020).

Making sense of urban system entanglements requires governance institutions to understand the nature of complex urban systems, but also their own role within it (Chester et al., Reference Chester, Miller, Muñoz-Erickson, Helmrich, Iwaniec, McPhearson, Cook, Grimm and Markolf2023). It also forces a rethinking of urban planning to embrace flexibility, uncertainty, and non-stationarity as fundamental to urban life, and the future of urban life (Alberti et al., Reference Alberti, McPhearson, Gonzalez, Elmqvist, Bai, Frantzeskaki, Griffith, Maddox, McPhearson, Parnell, Romero-Lankao, Simon and Watkins2018; Chester et al., Reference Chester, Miller, Muñoz-Erickson, Helmrich, Iwaniec, McPhearson, Cook, Grimm and Markolf2023). Fundamentally, urban systems, because of their inherent complexity, require new approaches that are not focused solely on efficiency as a means to sustainability (Elmqvist et al., Reference Elmqvist, Andersson, Frantzeskaki, McPhearson, Olsson, Gaffney, Takeuchi and Folke2019), but rather require modularity and redundancy and allow adaptive response to allow for flexibility, experimentation, and system innovation (Chester et al., Reference Chester, Miller, Muñoz-Erickson, Helmrich, Iwaniec, McPhearson, Cook, Grimm and Markolf2023; T. M. McPhearson et al., Reference McPhearson, Raymond, Gulsrud, Albert, Coles, Fagerholm, Nagatsu, Olafsson, Soininen and Vierikko2021). Resilience efforts in one area must not undermine others (Elmqvist et al., Reference Elmqvist, Andersson, Frantzeskaki, McPhearson, Olsson, Gaffney, Takeuchi and Folke2019).

Disruptions, extreme events, and disturbances of all kinds, including economic, social, political, climatological, and more, challenge not only planning, but everyday urban life (Dodman et al., Reference Dodman, Hayward, Pelling, Castan Broto, Chow, Chu, Dawson, Khirfan, McPhearson, Prakash, Zheng and Ziervogel2022). Understanding the complex relationships between urban development patterns and the processes that maintain ecosystem function and resilience in urban areas requires new frameworks and a new urban science (McPhearson, Iwaniec, et al., Reference McPhearson, Iwaniec and Bai2016).

Urban ecology in the late 1990s brought forward some of the first attempts to integrate a diversity of approaches from a broad set of disciplines to advance understanding of cities as complex, coupled human-natural systems (Alberti et al., Reference Alberti, Marzluff, Shulenberger, Bradley, Ryan and Zumbrunnen2003; Bai, Surveyer, et al., Reference Bai, Surveyer, Elmqvist, Gatzweiler, Güneralp, Parnell, Prieur-Richard, Shrivastava, Siri, Stafford-Smith, Toussaint and Webb2016; Grimm et al., Reference Grimm, Morgan Grove, Pickett and Redman2000; McPhearson, Pickett, et al., Reference McPhearson, Pickett, Grimm, Niemelä, Alberti, Elmqvist, Weber, Haase, Breuste and Qureshi2016). Urban scientists introduced mathematical rigor to the exploration of common urban properties across the world's cities and as high-resolution data have become increasingly available (Creutzig et al., Reference Creutzig, Niamir, Bai, Callaghan, Cullen, Díaz-José, Figueroa, Grubler, Lamb, Leip, Masanet, Mata, Mattauch, Minx, Mirasgedis, Mulugetta, Nugroho, Pathak, Perkins and Ürge-Vorsatz2022), urban science is delivering new insights for planning and policy-making. Yet the application of complexity to a budding transdisciplinary urban science remains at early stages, especially in the context of urban practices, policy, and planning.

Recognizing complexity requires a shift from viewing cities only as social-technological systems or social-ecological systems but rather as fully dynamic interacting social-ecological-technological systems, or SETS (Grimm et al., Reference Grimm, Cook, Hale and Iwaniec2015; McPhearson, Iwaniec, et al., Reference McPhearson, Iwaniec and Bai2016; McPhearson, Pickett, et al., Reference McPhearson, Pickett, Grimm, Niemelä, Alberti, Elmqvist, Weber, Haase, Breuste and Qureshi2016) involving the interactions and coevolution of social systems, living systems, and built and digital systems.

Complex adaptive systems hold the potential for emergent learning behaviors that support innovation (Folke et al., Reference Folke, Hahn, Olsson and Norberg2005; Lindsay, Reference Lindsay2018). Social and organizational learning (Mcleod, Reference Mcleod2020) can foster social cohesion and local stakeholder agency (Johannessen, Reference Johannessen2017). These processes include active participation for social change, consciously designed co-creation processes, learning by doing, and nurturing communities of knowledge and practice (Mendoza, Reference Mendoza2016). Especially in rapid change situations, such learning can enable adaptive capacities and system resilience (Berkes, Reference Berkes2017; Folke et al., Reference Folke, Hahn, Olsson and Norberg2005). Diversity in knowledge systems and stakeholders coupled with iterative learning and action cycles can enable “doing the knowing” (Collins, Reference Collins, Manfredo, Vaske, Rechkemmer and Duke2014). Bridging institutions and policy entrepreneurs are important as science-policy-practice interfaces (de Kraker, Reference de Kraker2017). Robust and inclusive monitoring, tracking and feed-back systems are a precondition for looped learning processes to build adaptive capacities and urban system resilience (Azouz & Salem, Reference Azouz and Salem2023). These understandings are vital for foreseeing participatory processes that result in positive shifts (van der Wal et al., Reference van der Wal, De Kraker, Offermans, Kroeze, Kirschner and van Ittersum2014).

We bring forward five aspects to be considered in tackling urban complexity:

1. 1. Polycentric governance structures are needed that not only break down domain siloes but engage the public sector in codesign that leverages multiple forms of knowledge and innovation (Ostrom, Reference Ostrom2010). Governance structures and practices thus need to recognize the interdependency across multiple domains of urban systems and create institutional arrangements fit to tackle these challenges.

2. 2. Moving beyond traditional “fail-safe” approaches (Kim et al., Reference Kim, Carvalhaes, Helmrich, Markolf, Hoff, Chester, Li and Ahmad2022) is needed to deliver “safe-to-fail” solutions in the Anthropocene. Infrastructure investments and design are plagued by a 20th century paradigm that still builds to specified challenges, for example levees and storm barriers that are built to deal with storm surges of a specific magnitude, but when design specs are exceeded, fail catastrophically. Green infrastructure as nature-based solutions is an example of more safe-to-fail systems that can be built with uncertainty in mind (McPhearson et al., Reference McPhearson, Kabisch and Frantzeskaki2023), and that are envisioned and designed from the beginning as approaches that recognize the role of infrastructure in transforming cities for resilience (Gilbert & Shi, Reference Gilbert and Shi2023), but situate urban nature as central to innovating solutions to address diverse, and growing challenges.

3. 3. Climate change and weather-related extreme events, financial disturbances, disease outbreaks and more can manifest and operate across and between multiple spatial and temporal scales requiring solutions to consider how to deploy and prepare for effective response at multiple scales.

4. 4. Big data, computation and AI create opportunities for understanding complexity in ways never before possible (Ilieva & McPhearson, Reference Ilieva and McPhearson2018). AI, for example, offers ways to use machine learning, deep learning, and generative approaches together with massive new and emerging data streams to learn patterns that can improve understanding and decision-making of urban processes (Creutzig et al., Reference Creutzig, Niamir, Bai, Callaghan, Cullen, Díaz-José, Figueroa, Grubler, Lamb, Leip, Masanet, Mata, Mattauch, Minx, Mirasgedis, Mulugetta, Nugroho, Pathak, Perkins and Ürge-Vorsatz2022). On the other hand, AI algorithms are very sensitive to initial data conditions, and as is now increasingly understood, can often exacerbate gender and other inequity or biases because of poor initial sampling, model building, or bias in the original coding (Galaz et al., Reference Galaz, Centeno, Callahan, Causevic, Patterson, Brass, Baum, Farber, Fischer, Garcia, McPhearson, Jimenez, King, Larcey and Levy2021), which can create bias in urban policy making turning actions even more maladaptive.

5. 5. Urban tinkering can be an approach for experimentation and learning and evolution over time (Elmqvist et al., Reference Elmqvist, Siri, Andersson, Anderson, Bai, Das, Gatere, Gonzalez, Goodness, Handel, Hermansson Török, Kavonic, Kronenberg, Lindgren, Maddox, Maher, Mbow, McPhearson, Mulligan and Vogel2018), bringing in the evolutionary context of living organisms as a strategy to dealing with complexity over time.

To advance research on complexity and governance of urban systems five guiding research questions emerge as given in Table 4. See Supplementary Material S2 for the full list of 24 research questions.

Table 4.

Guiding research questions and ranking for “negotiate complexity and systemic risks”

3.5. Navigate environmental change

The process of rapid urbanization and the way cities are currently designed and built creates environmental impacts within and beyond their boundaries—climate change, land use change, biogeochemical cycles, loss of biodiversity and ecosystem decline, waste production, and pollution of air, water and soil, waste—many of which have human health and wellbeing impacts within and beyond cities (N. B. Grimm et al., Reference Grimm, Faeth, Golubiewski, Redman, Wu, Bai and Briggs2008). Recent decades have seen further exacerbation of existing problems and emergence of new challenges, driven by the complex interactions across environmental domains and with socioeconomic factors. For example, in addition to the effect of global warming, urban land use and air pollution cause heavy rainfall, resulting in unprecedented flooding in cities (Shi et al., Reference Shi, Bai, Kong, Fang, Gong, Zhou, Guo, Liu, Dong, Wei, He, Yu, Wang, Ye, Yu and Chen2017). Thus, while environmental problems are long standing and have attracted numerous research, understanding, managing and navigating through environmental change remains one of the top priority research themes.

In the context of a changing climate, local policies for mitigation and adaptation, their estimated emissions and risk reductions (Franco et al., Reference Franco, Melica, Treville, Baldi, Palermo, Bertoldi, Pisoni, Monforti-Ferrario and Crippa2024), and co-benefits are critical, including for air quality (Ulpiani et al., Reference Ulpiani, Pisoni, Bastos, Monforti-Ferrario and Vetters2025) and SDG linkages (Pradhan et al., Reference Pradhan, Joshi, Dahal, Hu, Subedi, Putra, Vaidya, Pant, Dhakal, Hubacek, Rupakheti, Roberts and van den Hurk2025). Cities often require addressing environmental changes jointly and co-designing visions together with their citizens and stakeholders in collaboration, including for climate neutrality (Kılkış, Ulpiani, et al., Reference Kılkış, Ulpiani and Vetters2024). Priorities in the process of navigating environmental change can also vary given the diversity of urban areas and diversity of vulnerabilities across neighborhoods, encompassing those with the largest carbon footprints (Sun et al., Reference Sun, Mi, Sudmant, Coffman, Yang and Wood2022) and lower emitters where vulnerabilities may be greatest. Cities can be holders of opportunities to navigate through global and local environmental changes by providing solutions and actions.

Recent decades have seen significant growth in the literature linking urbanization and cities to local, regional and global environmental change (Bai et al., Reference Bai, McPhearson, Cleugh, Nagendra, Tong, Zhu and Zhu2017). Starting from biodiversity, patches of urban areas were seen even in 12.6% of global protected areas in 2015 (G. Li et al., Reference Li, Fang, Li, Wang, Sun, He, Qi, Bao, Ma, Fan, Feng and Liu2022). In the future, about 13.2% to 19.8% of global protected and 93% of the Global 200 ecoregions may be affected by urban expansion (G. Li et al., Reference Li, Fang, Li, Wang, Sun, He, Qi, Bao, Ma, Fan, Feng and Liu2022). The total biodiversity footprint depends on those impacts that occur either directly in urban areas or due to activities that take place in urban areas with research gaps remaining (Mcdonald et al., Reference Mcdonald, Colbert, Hamann, Simkin, Walsh, Ascensão, Barton, Crossman, Edgecomb, Elmqvist, Gonzalez, Güneralp, Haase, Hillel, Huang, Maddox, Mansur, Paque, Pereira and Sharp2018). Biodiversity richness, including terrestrial and marine biodiversity (Jenkins & Van Houtan, Reference Jenkins and Van Houtan2016) depends closely on the interactions of urban areas with the local, regional and global environment. Marine litter, including plastic debris from coastal cities (Baudena et al., Reference Baudena, Ser-Giacomi, Jalón-Rojas, Galgani and Pedrotti2022), further extends the bounds of urban impacts on biodiversity. Better protecting the intactness of biodiversity (Schipper et al., Reference Schipper, Hilbers, Meijer, Antão, Benítez López, De Jonge, Leemans, Scheper, Alkemade, Doelman, Mylius, Stehfest, Van Vuuren, Van Zeist and Huijbregts2020) and bending the curve of biodiversity loss (Leclere et al., Reference Leclere, Obersteiner, Alkemade, Almond, Barrett, Bunting, Burgess, Butchart, Chaudhary, Cornell, De Palma, DeClerck, Di Fulvio, Di Marco, Doelman, Durauer, Ferrier, Freeman, Fritz and Young2018) requires concerted effort, including through compact urban form, ecological corridors, and environmentally conscious consumption patterns.

Over the 20^th and early 21^st centuries, almost 90% of urban source watersheds servicing 309 large cities experienced water quality degradation (McDonald et al., Reference McDonald, Weber, Padowski, Boucher and Shemie2016). In addition, around 44% of these large cities had a moderate or severe decline in their source watershed. Overall, the median population density in urban source watersheds increased by 5.4 times (McDonald et al., Reference McDonald, Weber, Padowski, Boucher and Shemie2016), further driving changes in water quality. Another study spanning over 2,000 watersheds for 317 cities found that average pollutant yields have increased by 40% for sediment pollution, 47% for phosphorus, and 119% for nitrogen (Chung et al., Reference Chung, Frank, Pokhrel, Dietz and Liu2021). By 2050, more than 1.7 billion people and up to 2.4 billion urban inhabitants are expected to face perennial or seasonal water scarcity, up from 933 million in 2016 (He et al., Reference He, Liu, Wu, Pan, Fang, Li and Bryan2021). Most of the water-scarce urban population resides and will reside in the Global South, particularly India and China (He et al., Reference He, Liu, Wu, Pan, Fang, Li and Bryan2021). Large cities are also involved in moving about 504 billion liters of water daily from source watersheds across 41% of the land surface (McDonald et al., Reference McDonald, Weber, Padowski, Flörke, Schneider, Green, Gleeson, Eckman, Lehner, Balk, Boucher, Grill and Montgomery2014).

The land on which urban areas are situated represents precious natural capital, biomes, and carbon sinks. While about 0.6 million km² in 2000, the total urban land area can range from 1.1 million to 3.6 million km² under different scenarios by the end of the 21^st century (Gao & O'Neill, Reference Gao and O'Neill2020), primarily driven by economic growth in some countries like China (Bai et al., Reference Bai, Chen and Shi2012), and population growth in others (Mahtta et al., Reference Mahtta, Fragkias, Güneralp, Mahendra, Reba, Wentz and Seto2022). Better urban policy, planning and design will continue to be critical in shaping spatial urban land patterns (Gao & O'Neill, Reference Gao and O'Neill2020). These decisions, in turn, have implications for climate action. Globally, however, land consumption is slightly faster than population growth (Schiavina et al., Reference Schiavina, Melchiorri, Freire, Florio, Ehrlich, Tommasi, Pesaresi and Kemper2022). Efficient development trajectories were more prevalent in the “Global South” than the “Global North” (Schiavina et al., Reference Schiavina, Melchiorri, Freire, Florio, Ehrlich, Tommasi, Pesaresi and Kemper2022), while requiring more improvements in all regions. Moreover, the places where new urban inhabitants will reside can exacerbate exposure to climate impacts. Currently 193 large cities with 1 million plus inhabitants are located in water-scarce regions (He et al., Reference He, Liu, Wu, Pan, Fang, Li and Bryan2021). In contrast, up to 1.1 billion urban inhabitants resided in low elevation coastal zones globally in 2015 with 300 million residing in the higher risk zone of less than 5 meters above sea level (MacManus et al., Reference MacManus, Balk, Engin, McGranahan and Inman2021).

Breathable clean air is a desperate need in polluted cities and a valuable asset in greener ones. A potential trade-off of better spatial connectedness and exposure to high PM_2.5 concentrations if additional measures are not taken can be observed (Liang & Gong, Reference Liang and Gong2020). Based on the most recent air quality database of the World Health Organization, less than 10% of the 6,743 settlements assessed had annual mean levels of particulate matter PM₁₀ or PM_2.5 concentrations within global air quality guidelines (WHO, 2024). While annual mean PM₁₀ or PM_2.5 concentrations were relatively constant across mega-cities in the last years, trends differed widely in cities with various sizes, developmental levels and different geographic regions (WHO, 2024). For a 10% increase in PM_2.5 concentrations, years of life lost can increase by about a factor of 1.6 or more (Juginović et al., Reference Juginović, Vuković, Aranza and Biloš2021). Beyond human health, environmental change, including air pollution, impacts urban plant phenology (Zhou, Reference Zhou2022). Collective flourishing of living beings within urban ecology requires a planetary health outlook while minimizing all environmental pollution types, including air pollution (Gabrys, Reference Gabrys2020).

Urban areas are pivotal for climate action based on both climate mitigation and adaptation (Dodman et al., Reference Dodman, Hayward, Pelling, Castan Broto, Chow, Chu, Dawson, Khirfan, McPhearson, Prakash, Zheng and Ziervogel2022; Revi et al., Reference Revi, Roberts, Klaus, Bazaz, Krishnaswamy, Singh, Eichel, Poonacha Kodira, Schultz, Adelekan, Babiker, Bertoldi, Cartwright, Chow, Colenbrander, Creutzig, Dawson, De Coninck, De Kleijne and Ürge-Vorsatz2022). Greenhouse gas emissions attributed to urban areas continue to increase based on existing trends of urbanization. Urban emissions from a consumption-based emissions perspective were 25 GtCO₂-eq in 2015 and 29 GtCO₂-eq in 2020 (IPCC, 2021). With insufficient action based on moderate to low mitigation efforts to change these trends, global consumption-based urban CO₂ and CH₄ emissions can rise to 34 GtCO₂-eq and above by 2050. Only with ambitious and immediate mitigation effort will urban areas be able to have near net-zero CO₂ and CH₄ emissions with about 3 GtCO₂-eq of consumption-based emissions in 2050 (Gurney et al., Reference Gurney, Kılkış, Seto, Lwasa, Moran, Riahi, Keller, Rayner and Luqman2022; IPCC, 2021). Shifting to renewable energy, active and shared mobility, reducing food waste, and dematerialization (Swilling et al., Reference Swilling, Hajer, Baynes, Bergesen, Labbé, Musango, Ramaswami, Robinson, Salat, Suh, Currie, Fang, Hanson, Kruit, Reiner, Smit and Tabory2018) take place among numerous demand side measures, including technology adoption and use of more efficient infrastructure (Creutzig et al., Reference Creutzig, Niamir, Bai, Callaghan, Cullen, Díaz-José, Figueroa, Grubler, Lamb, Leip, Masanet, Mata, Mattauch, Minx, Mirasgedis, Mulugetta, Nugroho, Pathak, Perkins and Ürge-Vorsatz2022). Climate change impacts in urban areas already affect health, livelihoods and infrastructure (IPCC, 2021). Transport, water, sanitation and energy systems in urban areas are and will continue to be impacted by extreme and slow-onset events, the increasing severity of which will depend on climate action (IPCC, 2021).

To advance research to enable cities to navigate environmental change, five research questions emerge as given in Table 5. See Supplementary Material S2 for the full list of 21 research questions.

Table 5.

Guiding research questions and ranking for “navigate environmental change”