Unexploited opportunities in understanding liveable and biodiverse cities. A review on urban biodiversity perception and valuation

Many researchers and policymakers from various disciplines highlight the role of urban biodiversity in delivering ecosystem services to enhance human wellbeing in a rapidly urbanising world. This suggests powerful synergies between approaches that are often disciplinarily separated, aiming either at human wellbeing or biodiversity conservation. Strategies towards liveable and biodiverse cities would gain support from insights into the people-biodiversity interface in cities. Yet, the question of which scale of biodiversity (from ecosystems to genes) benefits urban people in general and different socio-cultural groups in particular, remains largely open. To assess the current scientific knowledge as well as potential for further research, we systematically reviewed literature on people’s perception and valuation of urban biodiversity (200 studies). We also quantified the outcomes of studies in terms of the effects of biodiversity on valuation for studies that addressed biodiversity valuation below the ecosystem scale. We found that the current literature is critically biased in four ways. (1) Most studies cover temperate climates, while regions with the most pronounced urban growth are underrepresented. (2) Studies focus on urban forests and parks while important informal greenspaces are largely neglected. (3) Biodiversity is mostly addressed at the ecosystem scale (habitat or land-use types) while diversity at the species community or gene scale—key issues in biodiversity conservation—is covered to a much lesser extent. Most studies below the ecosystem scale show positive biodiversity effects, but universal patterns are not apparent due to the scarcity and low comparability of research. (4) Almost no studies consider the cultural diversity of urban residents by systematically targeting people from different socio-economic and cultural backgrounds or specific age groups. Our review reveals critical knowledge gaps about the people-biodiversity interface in cities, both in approaching cultural and biological diversity (‘biocultural diversity’). This shows unexploited opportunities and future directions in linking usually separated strategies on enhancing human wellbeing and biodiversity conservation in sustainable cities.     

Socio-economic and climatic changes lead to contrasting global urban vegetation trends

Urban greening can enhance quality of life by generating ecosystem services and has been proposed as a way of mitigating adverse consequences of global warming for human health. However, there is limited knowledge on global trends in urban vegetation and their relation to economic development and climate change. Here we studied 1,688 major cities worldwide and show that 70% (1,181) show an increase in vegetation derived from satellite observations (2000–2018). For 68% (1,138) of the cities studied, the increase in the urban vegetation is less strong as compared to the vegetation increase found in the surroundings of these cities. Overall, positive vegetation trends are widely observed in cities in Europe and North America, whereas negative vegetation trends in cities occur primarily in Africa, South America and Asia. Gross Domestic Product growth, population growth as well as temperature are found to be the main underlying drivers of the observed contrasts in changes in urban vegetation as compared to surrounding areas across continents. From a global synthesis of urban vegetation change, we quantify the role of social-economic development and climate change in regulating urban vegetation growth, and the contrasting imprint on cities of developed and developing countries.     

Urban green commons: Insights on urban common property systems

The aim of this paper is to shed new light on urban common property systems. We deal with urban commons in relation to urban green-space management, referring to them as urban green commons. Applying a property-rights analytic perspective, we synthesize information on urban green commons from three case-study regions in Sweden, Germany, and South Africa, and elaborate on their role for biodiversity conservation in urban settings, with a focus on business sites. Cases cover both formally established types of urban green commons and bottom-up emerged community-managed habitats. As our review demonstrates, the right to actively manage urban green space is a key characteristic of urban green commons whether ownership to land is in the private, public, the club realm domain, or constitutes a hybrid of these. We discuss the important linkages among urban common property systems, social–ecological learning, and management of ecosystem services and biodiversity. Several benefits can be associated with urban green commons, such as a reduction of costs for ecosystem management and as designs for reconnecting city-inhabitants to the biosphere. The emergence of urban green commons appears closely linked to dealing with societal crises and for reorganizing cities; hence, they play a key role in transforming cities toward more socially and ecologically benign environments. While a range of political questions circumscribe the feasibility of urban green commons, we discuss their usefulness in management of different types of urban habitats, their political justification and limitation, their potential for improved biodiversity conservation, and conditions for their emergence. We conclude by postulating some general policy advice.     

Quantifying urban water supply security under global change

Urban water supply security is commonly measured in terms of per capita water availability at the city level. However, the actual services that citizens receive are influenced by several components, including (1) a city's access to water, (2) infrastructure for its treatment, storage and distribution, (3) financial capital for building and maintaining infrastructure, and (4) management efficacy for regulating and operating the water system. These four types of "capital" are required for the provision of public water supply services. A fifth capital “community adaptation” is needed when public services are insufficient. Here, we develop and test an integrated framework for the quantification of urban water supply security based on these five capitals. “Security” involves three dimensions: 1) the level of system function (i.e., supply services); 2) risks to these services; and 3) robustness of system functioning. We apply this Capital Portfolio Approach (CPA) to seven urban case studies selected from a wide range of hydro-climatic and socio-economic regions on four continents. Detailed data on urban water infrastructure and services were collected in two cities, and key stakeholder interviews and household surveys were conducted in one city. Additional cities were assessed based on publicly available utility and globally available datasets. We find that in cities with high levels of public services, adaptive capacity remains inactive, while cities with high levels of water insecurity rely on community adaptation for self-provision of services. Inequality in the capacity to adapt leads to variable levels of urban water security and the vulnerability of the urban poor. Results demonstrate the applicability of the presented framework for the assessment of individual urban water systems, as well as for cross-city comparison of any type of cities. We discuss implications for policy and decision-making.     

Outstanding challenges for urban conservation research and action

Researchers, advocates and policymakers have proposed urban conservation as an emerging, integrative discipline that can contribute to sustainable cities by delivering co-benefits to human and non-human components of biodiversity. Given the recent growth in biodiversity-friendly designs and management schemes, there is an urgent need for a synthesis of this fragmented research base to inform planners and decision-makers. We conducted a systematic multidisciplinary literature review (787 papers) and found that the importance of urban areas for general conservation is not convincingly supported by empirical research. Only few studies demonstrated that cities can directly contribute to conservation efforts, by hosting viable populations of rare or endangered species, or by providing green corridors for the passage of natural populations. From a social perspective, while several studies demonstrated that green infrastructure could provide services for people (notably cultural services), only few studies explored the role of species diversity per se. Our review also shows strong geographical, location and taxonomic biases in urban biodiversity conservation research that make generalisations difficult. It is a disturbing paradox that while research in urban biodiversity conservation is rising exponentially, the main motivations for conserving urban biodiversity remain largely untested and unproven. We thus propose a framework for promoting integrative urban conservation research to bridge those gaps. Together, these findings warn against expanding cities under green planning and call for enhancing biodiversity experience by improving the quality of existing green spaces throughout the entire urban matrix. We provide a set of recommendations for practitioners and decision-makers to continue action.     

Strengthening conceptual foundations: Analysing frameworks for ecosystem services and poverty alleviation research

A research agenda is currently developing around the linkages between ecosystem services and poverty alleviation. It is therefore timely to consider which conceptual frameworks can best support research at this nexus. Our review of frameworks synthesises existing research on poverty/environment linkages that should not be overlooked with the adoption of the topical language of ecosystem services. A total of nine conceptual frameworks were selected on the basis of relevance. These were reviewed and compared to assess their ability to illuminate the provision of ecosystem services, the condition, determinants and dynamics of poverty, and political economy factors that mediate the relationship between poverty and ecosystem services. The paper synthesises the key contributions of each of these frameworks, and the gaps they expose in one another, drawing out lessons that can inform emerging research. Research on poverty alleviation must recognize social differentiation, and be able to distinguish between constraints of access and constraints of aggregate availability of ecosystem services. Different frameworks also highlight important differences between categories of services, their pathways of production, and their contribution to poverty alleviation. Furthermore, we highlight that it is important to acknowledge the limits of ecosystem services for poverty alleviation, given evidence that ecosystem services tend to be more associated with poverty prevention than reduction. We conclude by reflecting on the relative merits of dynamic Social–Ecological Systems frameworks versus more static checklists, and suggest that research on ecosystem services and poverty alleviation would be well served by a new framework distilling insights from the frameworks we review.     

More than planning: Diversity and drivers of institutional adaptation under climate change in 96 major cities

A key challenge for effective, ongoing urban climate adaptation is to adapt institutions within urban governance. While an extensive foundation of empirical knowledge on urban climate adaptation has accumulated over the last decade, our image of institutional adaptation continues to be dominated by a focus on planning. Whilst understandable, this can obscure a fuller range of areas in which institutional adaptation to climate change is being pursued. Furthermore, methodological path dependency in large-N analysis via a common focus on analyzing formal planning documents risks a skewed perspective as such documents may only offer a partial view. Building on the rich range of work to date assessing climate adaptation in cities, and notwithstanding continued major gaps such as in small-medium cities, we now need to find ways to examine the diversity of institutional adaptation occurring in practice, and to comparatively draw on the situated interpretive knowledge of case experts within individual cities to do so. With this aim in mind, this paper explores institutional adaptation in a specific domain (urban water) in a sample of 96 major cities across six continents through a survey of 319 case experts, examining the diversity of institutional adaptation across contexts and exploratively probing its drivers. Findings show that multiple forms of institutional adaptation are being jointly pursued in cities across all continents, leaning towards ‘softer’ rather than ‘harder’ forms, but nonetheless revealing a wide range of activity. Patterns in drivers suggest a political explanation for institutional adaptation (e.g. involving change agents and political pressure) rather than a rational one (e.g. involving response to climate-related risks and/or extreme events). Overall, there is a need to combine parsimony with expanded interpretive sensibility in advancing large-N research on institutional adaptation diversity in comparative perspective.     

Biodiversity mediates relationships between anthropogenic drivers and ecosystem services across global mountain,island and delta systems

Global change increasingly threatens nature, endangering the ecosystem services human wellbeing depends upon. Biodiversity potentially mediates these impacts by providing resilience to ecosystems. While biodiversity has been linked to resilience and ecosystem service supply on smaller scales, we lack understanding of whether mediating interactions between biodiversity and anthropogenic drivers are global and ubiquitous, and how they might differ between systems. Here, we examine the potential for biodiversity to mediate anthropogenic driver-ecosystem service relationships using global datasets across three distinct systems: mountains, islands and deltas. We found that driver-ecosystem service relationships were stronger where biodiversity was more intact, and weaker at higher species richness, reflecting the negative correlation between intactness and richness. Mediation was most common in mountains, then islands, then deltas; reducing with anthropogenic impact. Such patterns were found across provisioning and regulating ecosystem services, and occurred most commonly with climate change and built infrastructure. Further, we investigated the contribution of biodiversity and abiotic and anthropogenic drivers to ecosystem services. Ecosystem service supply was associated with abiotic and anthropogenic drivers alongside biodiversity, but all drivers were important to different ecosystem services. Our results empirically show the importance of accounting for the different roles that biodiversity plays in mediating human relationships with nature, and reinforce the importance of maintaining intact biodiversity in ecosystem functioning.     

On the Derivation of Input Parameters for Urban Canopy Models from Urban Morphological Datasets

Two techniques are analysed to derive mean street width and mean building width from morphological data of real cities: one based on a two-dimensional simplified morphology, and the other based on a three-dimensional regular simplified morphology. For each simplified morphology (two-dimensional and three-dimensional), the sky-view factors (street-to-sky) are computed and compared with the sky-view factors derived from the real morphology for selected districts of three European and two North American cities. The two-dimensional simplified morphology reproduces the real sky-view factors better than the three-dimensional morphology. Since many urban canopy parameterizations represent the city using simplified morphologies, this can be useful information for the derivation of input parameters for urban canopy parameterizations from real morphological data.     

Catalyzing sustainability pathways: Navigating urban nature based solutions in Europe

The notion that pathways can be identified and followed towards more sustainable futures has become an increasingly prevalent idea across the science and policy of global environmental change. Focusing on the debate within literatures on socio-technical systems, we find that pathways are often tied to the concept of scaling up such that they are dependent on trajectories which extend from the geographically small to large scale or from singular incidences to widespread adoption. Building on relational approaches to scaling, in this paper we argue that sustainability pathways need to be conceived as emerging from the catalytic interaction of multiple and overlapping efforts to change the status quo. We suggest that pathways can be conceptualized as being composed of ‘stepping stones’: bundles of related interventions that seize or create opportunities to build momentum for the implementation of innovations, the form of which is not predetermined. Drawing on 243 interviews, participant observation, and document analysis examining urban nature-based solutions across six European countries and the EU, we identify 20 stepping stones that can be used to accelerate the uptake of urban NBS in European cities. In the case of urban NBS in Europe, we find that the capacity of stepping stones to generate catalytic change strongly depends on how they interact with one another. We illustrate that pathways are not given but rather assembled through key interventions that collectively generate the capacities and momentum needed to overcome inertia and generate new socio-material orders in which such interventions are normalized as mainstream responses to sustainability challenges.     

Protected areas as a double edge sword: An analysis of factors driving urbanisation in their surroundings

Protected areas (PAs) are the most effective tools to protect biodiversity and ecosystem services. They have proven to be effective in stopping extensive land use conversion in well-conserved terrestrial ecosystems. However, land cover changes around PAs threaten biodiversity and ecosystem services within their limits and reduce ecological connectivity. In this study, we analysed the urban sprawls on the boundaries of 159 PAs (national, regional, and natural parks) in Spain, using 2.5 and 5 km non-protected buffer zones from 1990 to 2018. We clustered PAs based on biophysical and socio-economic characteristics and modelled urban sprawl in different buffers and periods. Hierarchical clustering revealed three groups of PAs: (a) proximate urban parks, (b) mountainous parks, and (c) parks in the Madrid autonomous region. We found that urbanisation in the surroundings of PAs in Spain has nearly doubled since 1990. General linear models explained a significant proportion of the urbanisation trends observed, with the number of municipalities in the boundary of the PA, the distance to a main road, and the distance to a big city acting as the most important drivers of urban sprawl. Our results also show that some PAs exert significant effects on urbanisation trends in their surroundings through the park-view effect. Finally, we highlight three coexisting phenomena that might explain the observed urban sprawl processes: (a) PAs attracting urbanisation in their surroundings due to the park-view effect, (b) PAs as a deterrent for urban sprawl within their limits, and (c) PAs occupying residual areas among previously urbanised lands.     

Urban greenspace as a climate change adaptation strategy for subtropical Asian cities: A comparative study across cities in three countries

Interest in nature-based approaches for climate change adaptation in cities is growing. Whilst there is a growing field of scholarship in a European and North America setting, research on the policy and governance of urban greenspace for climate adaptation in subtropical Asia is limited. Given the different development patterns, environmental characteristics and governance arrangements in subtropical cities, plus their comparatively large population and high climate risk, this is a significant knowledge gap. In response, this paper evaluates competences – skill sets, capabilities, and supporting policy and legislation – to enact adaptation through greenspace across different governance contexts; and assesses how international rhetoric on nature-based adaptation becomes localised to subtropical Asian city settings. We conduct interviews with stakeholders, plus review of relevant policy and city-specific research, for three cities with different governance and development contexts: Hanoi (Vietnam); Taipei (Taiwan); and Fukuoka (Japan). Across all three cases, we find that institutional structures and processes for connecting different remits and knowledge systems are a bigger challenge than a lack of appropriate policy or individuals with the required technical knowledge. However, opportunities for civil society participation and consideration of justice issues vary between the cities according to the socio-political context. These findings illustrate the value of individuals and organisations able to work across institutional boundaries in linking greenspace and adaptation agendas for subtropical Asian cities; and the importance of competence in collaboration with developers and civil society so that the rapid development or regeneration seen in subtropical Asian contexts does not tend towards green climate gentrification. More broadly, our findings show that the diverse nature of subtropical Asian cities means the role of greenspace in climate adaptation is likely to be context-specific, and thus that caution must be exercised against uncritically importing best practices from exemplar cases elsewhere.     

Cultural ecosystem services caught in a ‘coastal squeeze’ between sea level rise and urban expansion

Sea level rise and urbanization exert complex synergistic pressures on the provision of ecosystem services (ES) in coastal regions. Anticipating when and where both biophysical and cultural ES will be affected by these two types of coastal environmental change is critical for sustainable land-use planning and management. Biophysical (provisioning and regulating) services can be mapped using secondary data. We demonstrate an approach to mapping cultural ES by engaging stakeholders in iterative participatory mapping of personally and communally valuable cultural ES. We identify hotspots where highly valued cultural ES and high values for biophysical ES co-occur and generate spatially-explicit projections of sea level rise and urban expansion through 2060 to quantify impacts of the ‘coastal squeeze’ on ES. We study Johns Island, South Carolina, USA as an example of a vulnerable community in a low-lying region experiencing both rising water levels and a rapid influx of new residents and development. Our projections of environmental change through 2060 indicate that on Johns Island, cultural ES face disproportionately greater risk of decline than biophysical ES, with almost three quarters of the island’s cultural ES affected. We find that hotspots for cultural ES, such as community heritage sites and scenic vistas of oak-lined roads and marshes, rarely co-occur (only 3% area) with biophysical ES such as high values of carbon sequestration and agricultural production. This confirms the importance of engaging with local stakeholders to map cultural ES and puts them on a more level playing field with biophysical ES in decision-making contexts. Projected declines and limited overlap between biophysical and cultural ES highlight the need for tighter coordination between conservation and community planning, and for including locally valued cultural ES in assessments of threats posed by the ‘coastal squeeze’ of sea level rise and urban expansion.     

Global social and environmental change drives the management and delivery of ecosystem services from urban gardens: A case study from Central Coast,California

Urban community gardens are vital green spaces threatened by global social and environmental change factors. Population growth has reduced the amount of space available in cities, and climate change challenges plant growth thresholds. Urban community gardens provide dynamic socio-ecological systems to study how such social and environmental change factors affect the management and delivery of ecosystem services. They provide spaces where urban citizens purposefully interact with nature and receive multiple benefits. In this paper, we synthesize the results of three years of research in a case study of urban community gardens across the Central Coast of California and present a framework showing how both social and environmental change factors at the regional scale affect the ecological make-up of urban community gardens, which in turn affect the ecosystem services coming from such systems. Our study reveals that global environmental change felt at the regional level (e.g., increased built environment, climate change) interact with social change and policy (e.g., population growth, urbanization, water use policy), thus affecting regulations over garden resources (e.g., water availability) and management decisions by gardeners (e.g., soil management, crop planting decisions). These management decisions at the plot-scale, determine the ecological complexity and quality of the gardens and affect the resulting ecosystem services that come from these systems, such as food provision for both humans and urban animals. A greater understanding of how environmental and social change factors drive the management processes of urban community gardens is necessary to design policy support systems that encourage the continued use and benefits arising from such green spaces. Policies that can support urban community gardens to maintain ecological complexity and increase biodiversity through active management of soil quality and plant diversity have the potential to increase social and environmental outcomes that feedback to the larger environmental and social system.     

Rivers as municipal infrastructure: Demand for environmental services in informal settlements along an Indonesian river

In many developing world cities, where municipal infrastructure lags urban growth, lower-income communities may compensate by relying on local waterways to meet basic needs for water, sanitation, and recreational space. Access to these environmental services is possible because residents settle in floodplains, but thus entails elevated exposure to several water-related hazards, especially flooding. We examine this complex relationship in the neighborhoods of Bukit Duri and Kampung Melayu on the Ciliwung River in Jakarta, Indonesia. Based on a spatially referenced household survey, we analyze and map the patterns of use of six environmental services provided by the river: direct sanitary use, recreation, harvesting plants, groundwater use, solid waste disposal, and sewage disposal. Using spatial interpolation and regression methods, we identify the most probable areas where services are being used and analyze possible influences on this behavior. We find that proximity to the river significantly influences households’ behavior toward the river, as do infrastructure-related variables and neighborhing households’ behavior, while household demographic factors appear less significant. These results indicate that many households rely on multiple environmental services, and that residents most reliant on these services are also at greater risk of water-related hazards, service disruption (e.g., a decline in water quality), and potentially, eviction. This pattern of floodplain development is prevalent in many low-income countries, and a better understanding of how informal settlements rely on environmental services can be used to assess their vulnerabilities and inform more sustainable courses of development.     

Historical influences on the current provision of multiple ecosystem services

Ecosystem service provision varies temporally in response to natural and human-induced factors, yet research in this field is dominated by analyses that ignore the time-lags and feedbacks that occur within socio-ecological systems. The implications of this have been unstudied, but are central to understanding how service delivery will alter due to future land-use/cover change. Urban areas are expanding faster than any other land-use, making cities ideal study systems for examining such legacy effects. We assess the extent to which present-day provision of a suite of eight ecosystem services, quantified using field-gathered data, is explained by current and historical (stretching back 150 years) landcover. Five services (above-ground carbon density, recreational use, bird species richness, bird density, and a metric of recreation experience quality (continuity with the past) were more strongly determined by past landcover. Time-lags ranged from 20 (bird species richness and density) to over 100 years (above-ground carbon density). Historical landcover, therefore, can have a strong influence on current service provision. By ignoring such time-lags, we risk drawing incorrect conclusions regarding how the distribution and quality of some ecosystem services may alter in response to land-use/cover change. Although such a finding adds to the complexity of predicting future scenarios, ecologists may find that they can link the biodiversity conservation agenda to the preservation of cultural heritage, and that certain courses of action provide win-win outcomes across multiple environmental and cultural goods.     

Assessment of the management of organizations supplying ecosystem services from tropical forests

Global environmental change leads to degradation of tropical forests in many countries. In response to this pressure, programs for payments for ecosystem services (PES) are developing and organizations are emerging which manage forests in order to supply ecosystem services, rather than only harvest timber. Typically such services are carbon sequestration, biodiversity conservation, pollination, and watershed protection. Public or private actors interested to invest in or donate money for the provisioning of such services are faced with the problem of choosing the appropriate organization supplying ecosystem services. The goal of this paper was to develop an assessment framework based on the balanced scorecard concept including drivers, impact, performance and context variables. Results of a survey of international market actors were used to determine assessment criteria and their weights. Putting the focus of this paper on drivers and impacts, we assessed Latin American organizations that “sell” ecosystem services from tropical forests in terms of their general management, marketing, forest management, client and stakeholder satisfaction, and forest ecosystem status. We found that supplying organizations vary widely with respect to their achievements in these areas. However, the variance of assessment results is influenced even more by the variance in weights the international market actors allocate to the assessment criteria. The insights of this study can contribute to the continuous improvement of management processes in supplying organizations and can support investors and donors in their decision-making with respect to organization supplying ecosystem services.     

Negotiating Indigenous benefits from payment for ecosystem service (PES) schemes

This paper draws on research conducted with Aboriginal land managers across Northern Australia to show how and why payments for ecosystem service (PES) schemes should be framed around Indigenous rights to and relationships with their traditional estates. PES schemes offer opportunities to recognize and support Aboriginal communities' land and sea management knowledge and practices, and there is strong evidence that Indigenous communities are seeking to engage with such schemes. We focus on Aboriginal savanna landscape management, particularly traditional burning practices, to extend the ecosystem services framework to recognize Indigenous values and interactions with their lands as a critical service for Indigenous well-being. Drawing on case-study analysis of PES projects negotiated to support Aboriginal fire management programs across Northern Australia, we show how cultural ecosystem services can be applied to represent the active, dynamic and often interdependent relationships inherent in Indigenous human-environment relationships.     

The challenge of valuing ecosystem services that have no material benefits

Since the Millennium Ecosystem Assessment, ecosystem service science has made much progress in framing core concepts and approaches, but there is still debate around the notion of cultural services, and a growing consensus that ecosystem use and ecosystem service use should be clearly differentiated. Part of the debate resides in the fact that the most significant sources of conflict around natural resource management arise from the multiple managements (uses) of ecosystems, rather than from the multiple uses of ecosystem services.If the ecosystem approach or the ecosystem service paradigm are to be implemented at national levels, there is an urgent need to disentangle what are often semantic issues, revise the notion of cultural services, and more broadly, practically define the less tangible ecosystem services on which we depend. This is a critical step to identifying suitable ways to manage trade-offs and promote adaptive management.Here we briefly review the problems associated with defining and quantifying cultural ecosystem services and suggest there could be merit in discarding this term for the simpler non-material ecosystem services. We also discuss the challenges in valuing the invaluable, and suggest that if we are to keep ecosystem service definition focused on the beneficiary, we need to further classify these challenging services, for example by differentiating services to individuals from services to communities. Also, we suggest that focussing on ecosystem service change rather than simply service delivery, and identifying common boundaries relevant for both people and ecosystems, would help meet some of these challenges.     

Cascades of green: A review of ecosystem-based adaptation in urban areas

Climate change impacts increase pressure on challenges to sustainability and the developmental needs of cities. Conventional, “hard” adaptation measures are often associated with high costs, inflexibility and conflicting interests related to the dense urban fabric, and ecosystem-based adaptation (EbA) has emerged as a potentially cost-efficient, comprehensive, and multifunctional approach. This paper reviews and systematises research on urban EbA. We propose an analytical framework that draws on theory from ecosystem services, climate change adaptation and sustainability science. It conceptualises EbA in terms of five linked components: ecological structures, ecological functions, adaptation benefits, valuation, and ecosystem management practices.Our review identified 110 articles, reporting on 112 cities, and analysed them using both quantitative statistical and qualitative content analysis. We found that EbA research in an urban context is fragmented due to different disciplinary approaches and concepts. Most articles focus on heat or flooding, and the most studied ecological structures for reducing the risk of such hazards are green space, wetlands, trees and parks. EbA is usually evaluated in bio-geophysical terms and the use of economic or social valuations are rare. While most articles do not mention specific practices for managing ecological structures, those that do imply that urban EbA strategies are increasingly being integrated into institutional structures. Few articles considered issues of equity or stakeholder participation in EbA.We identified the following challenges for future EbA research. First, while the large amount of data generated by isolated case studies contributes to systems knowledge, there is a lack of systems perspectives that position EbA in relation to the wider socio-economic and bio-geophysical context. Second, normative and ethical aspects of EbA require more thought, such as who are the winners and losers, especially in relation to processes that put people at risk from climate-related hazards. Third, there is room for more forward-looking EbA research, including consideration of future scenarios, experimentation in the creation of new ecological structures and the role of EbA in transformative adaptation.