Strategic planning for urban nature-based solutions
Creators: name: Croeser, Thami
Publisher: name: RMIT University
Year: 2024
Subjects: classificationCode: 330404
subject: Land use and environmental planning
classificationCode: 410401
subject: Conservation and biodiversity

description: Nature-based solutions (NBS) show immense potential to improve urban areas. The use of NBS including trees, parks, green roofs and green walls has been shown to offer a wide variety of benefits in cities. These include mitigation of the urban heat island effect, improved water quality of runoff, the provision of habitat for native species, flood mitigation and improved physical and mental health of urban residents. 

While the concept of nature-based solutions is compelling and supported by a substantial evidence base, most cities have been slow to deliver NBS outside of isolated pilot projects. Against a backdrop of rapid urban development, this slow rollout often equates to a net loss of urban vegetation as development displaces street trees and private gardens. This gap in implementation endures despite the rising popularity of NBS in practitioner circles, with a significant emergence of NBS strategies and projects in cities around the world in the last decade. This non-delivery – which I frame as an ‘implementation gap’ – means that cities are likely to fall significantly short of important strategic targets. A wide range of studies have attributed the slow delivery of NBS to barriers within the institutions responsible for NBS delivery. Institutions are often resistant to change in their practices and/or poorly equipped to adopt new approaches. NBS delivery at scale demands new rules, systems and processes, significant additional resources, and a range of new ways of working and thinking in urban areas. 

This thesis offers four distinct pieces of published research that address practical challenges in NBS delivery by offering new tools to practitioners. To advance theoretical understanding of the problem, my work also seeks to offer new insight into the barriers to NBS implementation, and highlights the scale of change that will be required to close it.

In my first chapter, I demonstrate how reallocation of street parking to green space in central city areas could deliver extensive new areas of canopy, understorey, and permeable green space. Importantly, this could be delivered with no net loss of parking, as garage parking is abundant and poorly utilised in central-city areas; up to half of the city’s street parking spaces are within 200m of a vacant garage parking space. I show that converting these redundant street spaces to biodiverse green space could deliver a third of the city’s canopy cover target, while meeting a number of challenging stormwater targets, and improving ecological connectivity. 

Retaining trees is as important as planting new trees. Chapter two demonstrates a way of monitoring removals of trees in urban areas experiencing rapid infill development. I show that the small net changes in total tree canopy are the product of surprisingly large dynamics of growth and loss. I find that Melbourne’s innermost municipality lost over ten thousand trees in under a decade, equating to many hectares of canopy cover. This effectively negated significant canopy growth arising from the city’s planting programs. This highlights the importance of tree protection; if cities are able to reduce losses, they could realise much more rapid net growth in canopy. 

Selecting the right NBS is an important planning challenge, particularly given the growing diversity of NBS approaches. My third chapter presents a tool to guide NBS selection in cities preparing NBS strategies. The tool was prepared in the context of a large European Union funded project where a very diverse set of cities were selecting NBS to solve problems including flooding, heat island effects and air pollution. The tool uses multicriteria decision analysis to guide selection from 43 different NBS options to both optimise co-benefits and encourage selection of achievable NBS options. This chapter examines the results of the tool as well as testing its operation, interviewing users in seven cities to verify the value of the tool in practice. 

My fourth research chapter addresses the ‘implementation gap’ more directly, offering a diagnostic tool that practitioners can use to examine their organisation’s capabilities to deliver NBS. I define eight broad success factors for NBS delivery, each of which has a number of elements. The tool tests capability within each success factor, and produces a diagnosis of delivery capacity. In many cases, I found that cities were hampered by multiple severe shortfalls in important success factors. While capacity building remains a rare aspect of NBS strategy development, this study underlines that institutional reform is just as critical as ambitious targets or impressive pilot projects in cities that hope to see large-scale delivery of NBS. 

The final research chapter of this thesis is a brief theoretical reflection, considering the potential of action research to deliver innovative outcomes– such as NBS delivery by local government – in large collaborative projects. These projects often deliver exemplary results in the short term, but do not necessarily spark enduring change or replication. I argue that this relates to a tendency to neglect necessary institutional reform, such that obstructive systems are not changed, just briefly set aside, to enable delivery of innovations. I outline suggestions for the design of action research projects that are more likely to deliver lasting innovation, including explicitly considering a theory of change, and noting the critical role of senior leaders in spearheading new, reform-oriented innovation programs. 

The thesis concludes with a discussion of future research, and a reflection on the connections between the emergent issue of NBS delivery and the much larger socio-political phenomena that have shaped our cities in recent years.