Can’t see the forest for the trees (being removed)

The benefits of trees and other vegetation in cities is clear. As well as being aesthetically pleasing, green spaces cool our cities, treat air and water, provide space for recreation and connection, improve mental and physical wellbeing, and support habitat for biodiversity [1]. Our understanding of the importance of green space in cities is not new. In 17th century Paris, trees were used to affect air flow coming into the city. In the 19th century regional parks and later green belts and green wedges were proposed to remediate the legacies of the industrial revolution [2]. However, evidence for the multiple benefits and central importance of vegetation to urban livability is now much stronger, as is our understanding of the implications of changing climate and the role that urban vegetation plays in mitigating these impacts.

The challenge facing our cities

Trees and urban vegetation are a critical ingredient for liveable, resilient and sustainable cities, but with this comes a consideration of how to grow our cities’ green cover and effectively monitor these changes.

In many cases we plan, manage and develop our urban environments with vegetation features as an afterthought, as a ‘nice to have’ rather than an ‘essential to have’. Too often we manage trees in a reactive, piecemeal, and non-strategic way. We treat requests to remove trees in isolation, ignoring the role that trees plays in providing common benefits in urban settings - ignoring trees as part of a collective infrastructure. Understanding urban vegetation collectively as ‘Green Infrastructure’ is an important part of informing a more strategic and integrated approach to managing this critical urban infrastructure.

Our national study of urban forest management reveals that since 2013 the majority of urban local government areas are going backwards and losing green cover [3]. However, we found that in more recent years this trend is reversing with numerous examples of local governments that are gaining green cover – in most cases not enough to make up for losses, but the hope remains that the tide is turning. This means that in many areas the hard work of local government and community is beginning to pay off.

Frequently, requests to remove trees in urban environments are assessed through a narrow risk management focus with traditional infrastructure need prioritised. The risk of 'that tree' impacting on buildings, pipes or wires, of creating mess by dropping branches, or harbouring pests. Or the need to remove trees to widen a road or develop a property. There is nothing inherently wrong about prioritising infrastructure or taking a risk-based approach. In fact, this is central to effective management of the complex interacting systems that make up our cities. But such an approach must also acknowledge the magnitude and likelihood of negative impacts of tree removal and the benefits of tree retention. Only by viewing ‘that tree’ as part of the collective infrastructure can we properly understand the true risks of removal.

The importance of protecting green infrastructure on private land

Much like flood management in cities, the cumulative impact of small losses to green infrastructure can lead to a significant reduction in capacity of that infrastructure to provide benefits and reduce risks. And, much like with flood management, action is needed on both public and private lands to accrue benefit and reduce risks.

With private land typically accounting for the majority of tree canopy cover in our cities, decisions made by private landowners and managers can have a significant bearing on the extent of vegetation cover in our neighbourhoods [4]. In the context of flooding, there is a mature system of regulation, policy and management processes to ensure decisions made on private land do not systematically accumulate and result in flood disaster. For example, a landowner cannot simply discharge stormwater runoff anywhere from a property; water flow pathways through private lots in land subject to flooding must be preserved; and in many areas, a proportion of permeable surfaces must be maintained. All these measures ensure that private land does not increase flood risk for the broader community.

The same logic applied to stormwater and other urban infrastructure should apply to green infrastructure. The location and distribution of vegetation matters in order to maximise the benefits delivered to our communities - for example, see our research on the cooling impact of vegetation and built form configuration [5]. All urban residents need and deserve quality green infrastructure coverage, to cool their neighbourhoods in summer, underpin physical and mental wellbeing, and provide everyday contact with nature.

As our cities restructure, increasing population densities and reducing the amount of open space and permeable surfaces, we must take an integrated and strategic approach to green infrastructure, ensuring both public and private landholdings play their part in maintaining and enhancing green infrastructure to maximise benefits provided to all urban citizens and biodiversity.

While the understanding of the importance of green infrastructure in cities is growing, with an associated increase in action to maintain and preserve this valuable asset, most action in this space in Australia and abroad has focused on public land. Our research found that local government officers are leading the charge for better urban forest management with significant progress being made to enhance vegetation on public land. Averting the loss of trees on private land, however, while recognised as being critical, often lands in the ‘too-hard basket’ [3]

In response, we recently reviewed innovative regulations and incentives aimed at protecting and retaining trees on private urban land. [6]. We found that the most innovative mechanisms combine two or more regulations, instead of relying on a single directive, and/or use financial incentives to retain or plant trees in newly developed or redeveloped sites, as well as private residences. However, we also found no jurisdiction where there was comprehensive and effective management of the urban forest on private land, confirming the need for innovation and leadership in this space.

The way forward

For urban policy makers, practitioners and urban communities, the case for a more committed and strategic approach to managing green infrastructure on both public and private land is clear. There is also significant opportunity to learn from others to inform action. More effort and innovation is needed to establish shared understandings and purposes, develop a sound foundation of strategy, policy, regulation and incentives, and to develop practices and partnerships to deliver more effective urban forest management. Together, this will effectively protect and enhance trees and other forms of vegetation as critical infrastructure in cities.

AUTHOR ACKNOWLEDGEMENT

We acknowledge the Traditional Owners of the lands and waters where this research took place and pay our respects to Elders past and present. We acknowledge that all cities in Australia exist on Indigenous land and that this land was never ceded. Research featured in this article was supported by funding from the Australian Government’s National Environmental Science Program through the Clean Air and Urban Landscapes Hub; and Hort Innovation. We acknowledge the many fantastic research collaborators involved in producing the research featured.