On the one hand the Special Issue provides a diagnosis of the justice implications embedded in recent efforts to renature cities. Placed in the breadth of existing scholarship, it aims to explore the type of socio-environmental contradictions and contestations emerging through the deployment of nature-based solutions in a range of geographies. On the other hand, this Special Issue works towards shaping a prognosis, or a potential future for the governance of nature-based solutions, that brings social justice, indigenous knowledge and more-than-human thinking into the design and execution of projects on nature-based solutions. More generally, this Special Issue contributes to the growing literature in critical urban geography, planning and ecology on how different types of ‘natures’ are deployed and instrumentalized to defend dominant economic representations. Yet, for nature-based solutions to truly stand up to their promise, the logic and apparatus of urban development need to be decoupled from the ‘growth-at-all-costs’ mental cage by exploring degrowth narratives, for example as only then can environmental justice in its various manifestations be sought, defended and unfolded.
Habitat Type: URB
Urban environment
In water sector, nature-based solutions (NBS) are increasingly recognized as solutions to address societal challenges, while simultaneously providing human well-being and biodiversity benefits. NBS contribute to climate mitigation and adaptation, to increase flooding resilience of cities, reduce pollution, support biodiversity restoration, and enable ecosystems services provision. However, the implementation of nature-based water management solutions remains slow for several reasons. First, NBS are still novel concept, relatively unknown for many water-related stakeholders, necessitating more insight efforts to generalize their adoption. Moreover, concerns exist over their reliability, cost-effectiveness, and their long-term performance. Alongside those concerns, financial and governance barriers to implementing NBS exist, exhibiting additional needs for further research. Least but not last, technical barriers can also represent impediments in NBS implementation. In this communication, we consolidate the NBS definition comparatively to related infrastructures, such as natural, green or hybrid systems and synthesize the knowledge related to research and operational outcomes from fullscale implementation of nature-based water management solutions with the aim to identify delivered benefits but also potential drawbacks and requirements for a successful implementation. At the end, the ways to overcome the identified barriers and research recommendations are presented with the aim to foster the NBS implementation within water governance and urban planning sectors.
The world is warming at an unprecedented pace and humaninduced climate change has already caused widespread adverse impacts on people and nature (IPCC, 2022e). There are already observed increases in frequency and intensity of climate and weather extremes in every inhabited region of the world, including heat waves, heavy precipitation events that cause flooding, drought and fire and this is expected to intensify (IPCC, 2022e). Progress on the Sustainable Development Goals has been inhibited and the most vulnerable people are disproportionately affected (IPCC, 2022e). This is only the beginning as global temperatures will continue to rise until at least the middle of the 21st century in all currently possible emission scenarios. If deep emission cuts do not occur, the temperature will rise at least 2.1°C to 3.5°C or even up to 5.7°C by the end of the century (IPCC, 2021).
Nature-based solutions (NBS) have been central to the European Union’s drive to address climate change, ecological degradation, and promote urban prosperity. Via an examination of the Horizon 2020-funded URBAN GreenUP project in Liverpool, this paper explores mainstreaming NBS in city planning. It uses evidence from pre- and post-intervention surveys with Liverpool residents and interviews with local business, environmental, government, and community sector experts to illustrate how a complex interplay of scale, location, focus, and visibility of NBS influences perceptions of the added value of NBS. This paper highlights the requirement that NBS interventions be bespoke and responsive to the overarching needs of residents and other stakeholders. Moreover, we underscore the importance of expert input into the design, location, and maintenance of NBS and call for these key drivers of successful delivery to be better integrated into work programs. This paper also notes that the type and size of NBS interventions impact perceptions of their value, with smaller projects being viewed as less socially and ecologically valuable compared to larger investments. We conclude that while small-scale NBS can support climatic, health, or ecological improvements in specific instances, strategic, larger-scale, and more visible investments are required to accrue substantive benefits and gain acceptance of NBS as a legitimate and effective planning tool.
Background
High ambient temperatures are associated with many health effects, including premature mortality. The combination of global warming due to climate change and the expansion of the global built environment mean that the intensification of urban heat islands (UHIs) is expected, accompanied by adverse effects on population health. Urban green infrastructure can reduce local temperatures. We aimed to estimate the mortality burden that could be attributed to UHIs and the mortality burden that would be prevented by increasing urban tree coverage in 93 European cities.
Methods
We did a quantitative health impact assessment for summer (June 1–Aug 31), 2015, of the effect of UHIs on all-cause mortality for adults aged 20 years or older in 93 European cities. We also estimated the temperature reductions that would result from increasing tree coverage to 30% for each city and estimated the number of deaths that could be potentially prevented as a result. We did all analyses at a high-resolution grid-cell level (250 × 250 m). We propagated uncertainties in input analyses by using Monte Carlo simulations to obtain point estimates and 95% CIs. We also did sensitivity analyses to test the robustness of our estimates.
Findings
The population-weighted mean city temperature increase due to UHI effects was 1·5°C (SD 0·5; range 0·5–3·0). Overall, 6700 (95% CI 5254–8162) premature deaths could be attributable to the effects of UHIs (corresponding to around 4·33% [95% CI 3·37–5·28] of all summer deaths). We estimated that increasing tree coverage to 30% would cool cities by a mean of 0·4°C (SD 0·2; range 0·0–1·3). We also estimated that 2644 (95% CI 2444–2824) premature deaths could be prevented by increasing city tree coverage to 30%, corresponding to 1·84% (1·69–1·97) of all summer deaths.
Interpretation:
Our results showed the deleterious effects of UHIs on mortality and highlighted the health benefits of increasing tree coverage to cool urban environments, which would also result in more sustainable and climate-resilient cities.
While the amount of research on NBS is growing rapidly, there is a lack of evidence on community experiences of NBS design and implementation, particularly from low-income and informal settlements of African cities. This article adds new empirical evidence in this space through grounded analysis of NBS “niche” projects co-developed by intermediary organizations and communities in five sites across three settlements in Nairobi and Dar es Salaam. Findings are organized around four established NBS knowledge gaps: (1) NBS-society relations; (2) Design; (3) Implementation; (4) Effectiveness. We find that across the five studied sites, residents’ perceptions and valuation of urban nature has changed through processes of co-design and co-implementation, enabling community ownership of projects, and hence playing a crucial role in NBS effectiveness over time. The integration of gray components into green infrastructure to create hybrid systems has proven necessary to meet physical constraints and communities’ urgent needs such as flood mitigation. However, maintenance responsibilities and cost burdens are persisting issues that highlight the complex reality of NBS development in informal settlements. The cases highlight key considerations for actors involved in NBS development to support the replication, scaling up and institutionalization of NBS. These include the need to: (i) develop forms of engagement that align with co-production values; (ii) capture communities’ own valuation of and motivations with NBS development for integration into design; (iii) elaborate technical guidance for hybrid green-gray infrastructure systems that can be constructed with communities; and (iv) help define and establish structures for maintenance responsibilities (especially governmental vs. civil society) that will enhance the environmental stewardship of public spaces.
Many cities around the world are experimenting with nature-based solutions (NbS) to address the interconnected climate-, biodiversity- and society-related challenges they are facing (referred to as the climate–biodiversity–society, or CBS, nexus), by restoring, protecting and more sustainably managing urban ecosystems. Although the application of urban NbS is flourishing, there is little synthesized evidence clarifying the contribution of NbS in addressing the intertwined CBS challenges and their capacity to encourage transformational change in urban systems worldwide. We map and analyse NbS approaches specifically for climate change adaptation across 216 urban interventions and 130 cities worldwide. Results suggest that current NbS practices are limited in how they may comprehensively address CBS challenges, particularly by accounting for multidimensional forms of climate vulnerability, social justice, the potential for collaboration between public and private sectors and diverse cobenefits. Data suggest that knowledge and practice are biased towards the Global North, under-representing key CBS challenges in the Global South, particularly in terms of climate hazards and urban ecosystems involved. Our results also point out that further research and practice are required to leverage the transformative potential of urban NbS. We provide recommendations for each of these areas to advance the practice of NbS for transformative urban adaptation within the CBS nexus.
Justice and fairness have become key considerations in sustainability pathways and nature-based solutions (NBS), following activists and critical scholars who have long argued that the urban environment is an inherently political space that requires an analysis of benefits and burdens associated with its existence, use, and access. However, what justice means and how it is expressed, recognized, or achieved is often implicit in the literature on NBS, even though underlying notions of justice shape the analysis done and actions proposed. This paper starts from the premise that justice knows many different interpretations, therefore warranting scholars and practitioners working on NBS to carefully consider the differences and frictions between competing meanings of justice. Drawing from the history of social and environmental justice theory, we give an account of some key justice dilemmas and discuss their tenets as it relates to the end, means, and participants in the making of justice. From this, we draw out questions and commitments academics and practitioners in the NBS space should grapple with more explicitly. We argue that the emergent tension between pragmatic policy approaches and critical theoretical engagement is hindering a version of NBS that goes beyond a reflection of the justice implications of NBS to ensuring that NBS contributes to the furthering of justice. We advocate for the inclusion of critical social sciences and humanities perspectives and approaches beyond tokenism to instead encourage ontological, epistemological, and political reflection of the work academics and practitioners do in the NBS space.
Globally, the need for railways to adapt to the impacts of climate change is increasing rapidly. Nature-based Solutions (NbS) have been identified as potential climate change adaptation (CCA) options for rail infrastructure; however, the limited number of examples of their application on railways highlights that many factors still need to be considered to enable their wider implementation. This study identifies barriers to NbS uptake by the rail industry through a systematic literature review, categorising them into seven key themes, whilst also considering potential tools to facilitate their uptake. The ongoing development of NbS standards and guidance is confirmed as a means to resolve the barriers likely to be faced. A framework to support the uptake of NbS in the rail industry is presented and discussed in the context of the existing literature, with climate change risk assessments being recognised as the entry point for CCA in rail infrastructure management.
Cities increasingly have to find innovative ways to address challenges arising from climate change and urbanization. Nature-based solutions (NBS) have been gaining attention as multifunctional solutions that may help cities to address these challenges. However, the adoption and implementation of these solutions have been limited due to various barriers. This study aims to identify a taxonomy of dominant barriers to the uptake and implementation of NBS and their relationships. Fifteen barriers are identified from the literature and expert interviews and then ranked through a questionnaire. Interpretive Structural Modeling (ISM) serves to identify the mutual interdependencies among these barriers, which results in a structural model of six levels. Subsequently, Cross-impact matrix multiplication applied to classification (MICMAC analysis) is used to classify the barriers into four categories. The results suggest that political, institutional and knowledge-related barriers are the most dominant barriers to NBS. Cities that intend to apply NBS can draw on these findings, especially by more effectively prioritizing and managing their actions.
Transformative governance is key to addressing the global environmental crisis. We explore how transformative governance of complex biodiversity–climate–society interactions can be achieved, drawing on the first joint report between the Intergovernmental Panel on Climate Change and the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services to reflect on the current opportunities, barriers, and challenges for transformative governance. We identify principles for transformative governance under a biodiversity–climate–society nexus frame using four case studies: forest ecosystems, marine ecosystems, urban environments, and the Arctic. The principles are focused on creating conditions to build multifunctional interventions, integration, and innovation across scales; coalitions of support; equitable approaches; and positive social tipping dynamics. We posit that building on such transformative governance principles is not only possible but essential to effectively keep climate change within the desired 1.5 degrees Celsius global mean temperature increase, halt the ongoing accelerated decline of global biodiversity, and promote human well-being.
Nature-based solutions have emerged as a concept for integrating ecosystem-based approaches whilst addressing multiple sustainable development goals. However, implementing nature-based solutions is inherently complex and requires consideration of a range of environmental and socio-economic conditions that may impact on their effectiveness. This research assesses ecosystem services within the Valletta urban agglomeration, Malta, and evaluates the implications arising from existing distributional patterns. Proxy-based indicators and expert knowledge were used to map and assess a set of 14 ecosystem services. Proximity and correlation analyses were used to assess distributional inequalities arising from differentiated availability of ecosystem types with high ecosystem service capacities for groups with different socio-economic characteristics. Data relating to schooling, employment, sickness, disability, and old age, were combined to identify areas of relative advantage and disadvantage. The highest ecosystem service capacities were in the urban fringes and the lowest in dense urban cores. Private gardens and urban trees had the highest regulating ecosystem service capacities per unit area. Contrastingly, public gardens had low effectiveness for regulating ecosystem services but the highest cultural ecosystem service capacities. Availability of urban green infrastructure and tree cover differ according to socio-economic advantage, and disadvantaged communities generally had reduced proximity to ecosystems with high ecosystem service capacities. Considering these findings, we argue that urban ecosystem service assessments can support greening strategies by identifying the most effective nature-based solutions that can play a redistributive role by addressing existing inequalities in green infrastructure and ecosystem services capacities distribution in cities.
The new frontiers of sustainable cities should focus on urban planning tools and strategies that are able to integrate ecosystem services in urban development. An important step could include the design of nature-based solutions (NbSs) for introducing important ecological functions aiding human well-being and mitigating the loss of soil. In this study, we propose a methodology to analyse, in a spatial way, the effect of land use scenarios generated by urban planning in the provision of ecosystem services. The methodology analyses the variation of ecosystem services, considering the ecosystem services of the study area and their potential roles in changing the functions of planned urban actions as the starting point. One scenario of analysis includes the integration of NbSs into urban planning. The case study is that of a peri-urban area, characterized by an agroecosystem, which is intended for urban development in the municipality of Gallipoli, Southern Italy. The analysis highlights a low provision of ecosystem services by the agroecosystem, which has had the effect of important olive trees being destroyed by Xylella fastidiosa bacteria. Thus, the integration of NbSs and reducing the construction of buildings in the urban neighbourhood plan could improve the quantity of ecosystem services in the area. Moreover, the ecological design of ecosystem services could improve the typology of ecosystem services provision in the area in consideration of the starting points. Therefore, the analysis of the capacity to integrate ecosystem services in urban planning at the neighbourhood scale could be a tool of ecological urban design, useful to support the decision-making processes.
There is increasing global interest in employing nature-based solutions, such as reforestation and wetland restoration, to help reduce water risks to economies and society, including water pollution, floods, droughts and water scarcity, that are likely to become worse under future climates. Africa is exposed to many such water risks. Nature-based solutions for adaptation should be designed to benefit biodiversity and can also provide multiple co-benefits, such as carbon sequestration. A systematic review of over 10 000 publications revealed 150 containing 492 quantitative case studies related to the effectiveness of nature-based solutions for downstream water quantity and water quality (including sediment load) in Africa. The solutions assessed included landscape-scale interventions and patterns (forests and natural wetlands) and site-specific interventions (constructed wetlands and urban interventions e.g. soakaways). Consistent evidence was found that nature-based solutions can improve water quality. In contrast, evidence of their effectiveness for improving downstream water resource quantity was inconsistent, with most case studies showing a decline in water yield where forests (particularly plantations of non-native species) and wetlands are present. The evidence further suggests that restoration of forests and floodplain wetlands can reduce flood risk, and their conservation can prevent future increases in risk; in contrast, this is not the case for headwater wetlands. Potential trade-offs identified include nature-based solutions reducing flood risk and pollution, whilst decreasing downstream water resource quantity. The evidence provides a scientific underpinning for policy and planning for nature-based solutions to water-related risks in Africa, though implementation will require local knowledge.
The concept of NbS bridges between researchers and practitioners who search for innovative solutions to a wide range of societal problems and challenges, mostly related to ecological issues. Our conceptual paper aims at grounding the concept in theorizing NbS as a variant of ‘co-evolutionary technology’ CET, informed by ecological and institutional economics, and contextualized in recent Anthropocene research. This results in a new definition of NbS. NbS mediate between technosphere and biosphere evolution. We formulate four principles of CET, with the pivot of CET meeting both human needs and enhancing biospheric evolutionary potential, which feeds back on CET in co-creative design. The paper introduces core theoretical concepts, such as distributed agency and affordances, and proceeds in detailing CET along the standard tripartite view of technology, that is, design, production and use. We conclude in arguing that CET are inherently ethical since their design requires equal recognition of various human and non-human actors, both in terms of functions and ways of world-making.
Participation and citizen engagement are fundamental elements in urban regeneration and in the deployment of nature-based solutions (NBS) to advance sustainable urban development. Various limitations inherent to participatory processes concerning NBS for inclusive urban regeneration have been addressed, and lessons have been learnt. This paper investigates participation and urban regeneration and focuses on the development of guidelines for citizen engagement and the co-creation of NBS in the H2020 URBiNAT project. The methodology first involves the collection of scientific and practical input on citizen engagement from a variety of stakeholders, such as researchers and practitioners, to constitute a corpus of qualitative data. This input is then systematized into guideline categories and serves as the basis for a deeper analysis with researchers, experts, and practitioners, both inside and outside URBiNAT, and in dialogue with other cases of participatory NBS implementation. The results highlight an ‘ecology of knowledges’ based on a ‘living’ framework, which aims to address the specific needs of various segments of citizens and to match citizen engagement to the participatory cultures of cities. Implications and further research are also discussed, with a special focus on the implementation of NBS. The conclusions broaden the research context to include the refinement of the NBS approach, with participation being seen as both a means and an end.
Nature-based solutions (NBS) enable the ecosystem service benefits associated with natural landscapes to be embedded into the built environment, simultaneously providing environmental, social, and economic benefits. This represents a mechanism for renaturing cities that can address many of the interrelated challenges associated with urbanisation and climate change. If NBS can be delivered effectively on citywide scales, it presents an opportunity for the development of sustainable, resilient, and liveable cities. Examples of innovation in relation to planning and delivering NBS are emerging globally. However, the stewardship plan, an essential element of NBS that typically underpins the long-term success of these high-profile initiatives, is often overlooked or under-planned. Careful consideration of the technical, financing, and governance aspects of NBS stewardship can be critical to determining whether an NBS is able to deliver the multifunctional benefits for which it was designed, adapt to changing needs and environmental conditions, and avoid becoming a liability to those communities it was designed to benefit. Here we present a series of case studies demonstrating how innovation in NBS stewardship can secure and maximise the long-term success of NBS and avoid the legacy of neglected or poorly managed green wash.
Nature-based solutions (NBS) include a wide spectrum of situations: natural and seminatural green spaces, urban forests, designed gardens and parks, green road lines and roundabouts, bio-swales, productive gardens, green roofs and walls. In each site, the challenge is to provide the best solution according to the environmental and cultural context and the citizens’ demand. The urban horticulture in synergy with NBS provides to design, realise and manage green solutions for specific problems in the urban context. NBS supplies actions able to improve urban resilience and many opportunities for improving urban quality, optimising the delivering of a mixed range of ecosystem services (ES). This chapter highlights that NBS can be used for monitoring, soil, air and water quality, water matrices and pollinator diversity. We therefore describe methods for monitoring the quality of soil, air, water matrices and pollinator diversity and abundance. In conclusion, we point out some key aspects, under an interdisciplinary perspective, in order to promote further and deeper knowledge in the application of NBS in the urban environments.
Alongside the steep reductions needed in fossil fuel emissions, natural climate solutions (NCS) represent readily deployable options that can contribute to Canada’s goals for emission reductions. We estimate the mitigation potential of 24 NCS related to the protection, management, and restoration of natural systems that can also deliver numerous co-benefits, such as enhanced soil productivity, clean air and water, and biodiversity conservation. NCS can provide up to 78.2 (41.0 to 115.1) Tg CO2e/year (95% CI) of mitigation annually in 2030 and 394.4 (173.2 to 612.4) Tg CO2e cumulatively between 2021 and 2030, with 34% available at ≤CAD 50/Mg CO2e. Avoided conversion of grassland, avoided peatland disturbance, cover crops, and improved forest management offer the largest mitigation opportunities. The mitigation identified here represents an important potential contribution to the Paris Agreement, such that NCS combined with existing mitigation plans could help Canada to meet or exceed its climate goals.
This paper explores how varied systems of governance work at the European city level to deliver different policy mixes for implementing nature-based approaches which support integrated water management and policy. Urban systems provide unique insights here due to the concentration of consumption, economic activities and excessive land-use pressures. However, few studies are providing generic insights, rooted in policy and political theory perspectives, on the dynamic impact of urban governance systems on different mixes of policies to integrate urban nature and water management approaches. The paper fills this gap through an extensive literature review. It first draws on analysis that focuses on institutional logics of operation to understand how urban institutional arrangements of governance shape the framing of the policy problem and how this influences the choice of policy approaches. It then explores the related administrative processes including decision support tools, participatory approaches, and funding regimes. These administrative approaches deliver, potentially, different policy responses that take into account integrated nature-based policy approaches to urban water governance.
As cities increasingly turn to nature-based solutions to address key urban socio-ecological challenges, approaches to their governance, planning and implementation are increasingly important for ensuring their effectiveness. Nature-based solutions are multifunctional, and so their planning and implementation are by necessity interdisciplinary. As such, to support urban transitions with nature-based solutions, the role of intermediary actors deserves research attention. Intermediaries play key roles in linking between sectors, across different levels of government and between disciplines and policy domains. We identified three key points for research and planning nature-based solutions through intermediaries as key agents for change: intermediaries are creators of enabling institutional spaces needed for mainstreaming nature-based solutions in cities; intermediaries as actor configurations are dynamic over time and in context, and intermediation has to be understood as a fundamental governance activity in cities that want to scale up their climate adaptation planning with nature-based solutions. Using a case study of the development and initial implementation of the metropolitan urban forest strategy in Melbourne Australia, we analyze the multi-actor landscape that emerged, through the lens of intermediation. We systematically investigated which actors, partnerships and platforms acted as intermediaries in the transformative agenda of the Urban Forest strategy, how these actors interacted over the course of the strategy’s development and how their roles and functions shifted during the early implementation stages of the strategy. We found that an ‘ecology of intermediaries’ adopted a range of roles to support key functions including building collaboration, informing and disseminating policy learning, and strengthening political support. While intermediaries’ roles and functions shifted across the strategy’s development, their contributions were critical in the complex metropolitan governance context. Collaborative planning and governance for nature-based solutions in cities require intermediaries to remain topical, focused and inclusive/open to new ideas and lessons from innovations both emerging and driven.
Background
The COVID-19 pandemic has profoundly changed people’s ability to recreate in public green spaces, which is likely to exacerbate the psychological impacts of the pandemic. In the current study, we seek to understand whether greenery can support mental health even with insufficient outdoor exposure in times of physical isolation from the outdoor environment.
Methods
Between 17 May and 10 June, 2020, we conducted an online survey among 323 students (21.99 ± 3.10 years; 31% male) in health-related programs from two universities in the city of Plovdiv, Bulgaria. Severities of depressive and anxiety symptoms over the past two weeks were measured with the Patient Health Questionnaire 9-item and the Generalized Anxiety Disorder 7-item scale. We employed two self-reported measures of greenery experienced indoors (number of houseplants in the home and proportion of exterior greenery visible from inside the home) and two measures of greenery experienced outdoors (presence/absence of a domestic garden and availability of neighborhood greenery). Restorative quality of the home (the “being away” dimension of the Perceived Restorativeness Scale; PRS) and the neighborhood (the “being away” and “fascination” dimensions of the PRS), engagement with outdoor greenery (frequency of different types of interaction) and perceived social support were treated as mediators. Associations between greenery and mental health were tested using generalized linear regression and logistic regression. Structural equation modelling (SEM) techniques were used to test the theoretically-indicated relations among the variables.
Results
Clinically-meaningful symptoms of moderate depression and anxiety were reported by approximately 33% and 20% of the students, respectively. The relative abundance of greenery visible from the home or in the neighborhood was associated with reduced depressive/anxiety symptoms and lower depression/anxiety rates. Having more houseplants or a garden was also associated with some of these markers of mental health. As hypothesized, the mental health-supportive effects of indoor greenery were largely explained by increased feelings of being away while at home. Neighborhood greenery contributed to neighborhood restorative quality, which in turn facilitated social support and more frequent engagement with greenery, and that led to better mental health.
Conclusions
Students who spent most of their time at home during the COVID-19 epidemic experienced better mental health when exposed to more greenery. Our findings support the idea that exposure to greenery may be a valuable resource during social isolation in the home. However, causal interpretation of these associations is not straightforward.
The climate mitigation potential of urban nature-based solutions (NBSs) is often perceived as insignificant and thus overlooked, as cities primarily pursue NBSs for local ecosystem services. Given the rising interest and capacities in cities for such projects, the potential of urban forests for climate mitigation needs to be better understood. We modelled the global potential and limits of urban reforestation worldwide, and find that 10.9 ± 2.8 Mha of land (17.6% of all city areas) are suitable for reforestation, which would offset 82.4 ± 25.7 MtCO2e yr−1 of carbon emissions. Among the cities analysed, 1189 are potentially able to offset >25% of their city carbon emissions through reforestation. Urban natural climate solutions should find a place on global and local agendas.
Different ways of thinking and understanding urban problems and imagining solutions are needed to redress the suite of serious challenges facing cities. Focusing on urban nature, this conceptual paper begins from the standpoint that nature-based solutions (NBS) could help remake cities as places for more than just people; in other words, cities could encourage the flourishing of multiple species and ecosystems, including but not limited to, humans. Although cities were once considered ‘biodiversity wastelands’, they are now recognised as providing important habitat. However, NBS have been plagued by criticisms of anthropocentrism whereby human needs are prioritised over those of other species and ecosystems. To overcome this problem, the paper provides an outline of more-than-human thinking and suggests how relational concepts can help NBS move beyond an inherent anthropocentrism, and also begins to work through some of the complexities of making this shift. More-than-human thinking and theories have arisen in several disciplines, but despite a considerable presence in the literature, they have not yet been brought into conversation with NBS. The paper concludes that more-than-human thinking can generate deeper understanding of the interdependencies between all the entities that comprise cities, such that more inclusive NBS could be implemented.
Urban forests in northern Europe are threatened by climate change and biosecurity risks, and in response, city planners are urged to select a wider portfolio of tree species to mitigate the risks of species die-off. However, selecting the right species is a challenge, as most guidance available to specifiers focuses on ecosystem service delivery rather than the information most critical to tree establishment: the ability of a species to tolerate the stresses found in a given place. In this paper, we investigate the potential of using ecological techniques to describe ecological traits at the level of species selection, and the potential of functional ecology theories to identify species that are not widely discussed or specified at present but might be suitable. We collected trait data on 167 tree species across 37 genera, including 38 species within a case study genus, Magnolia L., and tested four theories that posit ways in which traits trade off against each other in predictable ways. We found that at this scale, most species recommended for urban forestry tend to be ordinated along an axis of variation describing pace of life and stress tolerance, and that most Magnolia species are described as being fast-growing rather than stress-tolerant, although there is a degree of inter-specific variation. Further, we found that only one theory offers a succinct and reliable way of describing physiological strategies but translating ecological theory into a form appropriate for urban forestry will require further work.