Trees or Townhouses?
Tensions between urban infill and urban forest policy objectives
The ACT Government’s urban infill policy aims for 70% of new housing to be built within Canberra’s existing urban footprint.
Urban densification is critically important to limit urban spread and reduce the environmental costs of land clearing for new developments . However, urban infill places significant pressure on existing trees as they are cleared for construction and infrastructure upgrades.
These pressures pose challenges to the ACT Government in meeting its target of 30% canopy cover across the urban footprint as set out in the Living Infrastructure Plan: Cooling the City and the ACT Climate Change Strategy 2019-2025 . Meeting this target requires an estimated 450,000 trees to be planted over the next 25 years, with the aim of mitigating the urban heat island effect and increasing Canberra’s climate resilience .
However, infill policies and practices will continue to reduce urban canopy cover unless adequate protections for existing and prospective trees are established.
Impacts of infill development on Canberra’s urban forest
In spite of legislated measures to protect trees, it's not uncommon for permission to be granted for trees to be removed to make way for development.
Even where tree protection measures are mandated as part of a development approval, issues may arise during construction that affect previously agreed upon measures.
The primary limitation affecting street trees is the space available on public verges as trees compete with public infrastructure.
Activities including network upgrades, exhuming disconnected services, installing new connection ties, establishing additional or wider driveways crossings, increased paths or pavements, new waste collection requirements, new parking bays and road upgrades may all affect existing trees.
These activities place pressure on street trees in multiple ways. For example, trees may be removed to create space, and the health of trees that remain may be impacted due to stringent pruning requirements or excavation occurring within the tree’s root zone.
Public infrastructure often requires a clearance zone to allow for servicing, which means there is also a risk that insufficient space may be left for new or replacement street tree plantings once works are completed.
Street verges and other open spaces are often used for ancillary purposes during construction due to lack of space on the development site, which may damage trees in these areas.
Common construction activities occurring on street verges include:
- access and setup space for construction vehicles and machinery
- contractor parking
- offloading and storage of materials
- site facilities
- scaffolding
Under the ACT planning system, the adverse impacts of development on public trees are often cumulative, occurring incrementally throughout the design and construction stages.
For example, development applications can be submitted in stages with successive proposals. While the initial development application may be submitted by the development proponent, the Landscape Management and Protection Plan can be submitted by a secondary proponent (e.g., builder), who has taken on the approved development application, which may increase damage to trees.
Some development projects also show a disconnect between the applicant and the eventual builder. In this scenario, a development proponent will submit and gain approval for a development that is then built by another party who may have difficulty constructing the development in accordance with the approved landscape management and/or composite verge plan, leading to damage or removal of trees that were previously protected.
Actions to mitigate policy tensions
Greater discussions between relevant policy areas on the challenges associated with achieving both 70% urban infill and 30% canopy cover targets in the ACT are required to resolve these policy tensions. These discussions could provide a forum to consider potential planning strategies to mitigate some of these conflicts and promote better landscape outcomes.
Promisingly, a review into the existing Municipal Infrastructure Standards was undertaken by the ACT Government in July 2023 to identify how the Standards could be updated to improve living infrastructure outcomes in both infill and greenfield development contexts.
A recommendation stemming from the review included creating an 'Infill Design Manual' to complement the Municipal Infrastructure Standards. This manual would provide a toolkit of design standards to increase canopy cover and surface permeability tailored to infill contexts. These standards recognise that each infill development will need to consider site-specific constraints and design opportunities to improve living infrastructure outcomes, which will be enabled through the use of exceptions to standard clearances.
