Urban trees and tree canopy cover are increasingly recognised as essential components of the cities and neighbourhoods where more than 90% of Australia's forecast population of 35 million will live by 2050.
International research and practice, to date, has responded to the challenge of sustaining multi-functional, large, long-lived trees within compact forms of development, amongst paved plazas and alongside roads and streets.
A range of techniques have been advanced that are capable of delivering adequate quality and quantity of space for tree root growth while maintaining pavement functionality, including: structural soil; soil filled load-bearing cells; suspended slab pavement along with permeable pavements.
Applications of these engineered surface and subsurface tree spaces in Australian cities has occurred over the last 20 years. However, their use has been limited, rarely monitored and is often perceived by developers, infrastructure authorities and local governments as a high cost, high-risk approach.
Yet these same stakeholders are increasingly attentive to the opportunities that green infrastructure components offer to community health and well-being, tourism, business vitality, property value improvement, place making, buffering urban microclimate, managing local stormwater, air quality improvement, and so much more.
This national study proposes a range of monitored, long-term trials in Australian cities to advance best practices and build knowledge sharing. Complementary qualitative research is also proposed to explore the barriers to implementation and to collate the learnings from existing installations of surface and subsurface tree spaces.
TREENET, as a reputable, independent non-profit organisation dedicated to improving the urban forest, sees facilitating this special research project as critical to building home-grown evidence to support those designing our cities for trees.
- Permeable pavement excavations root penetrations (marked by the triangles) occupied a relatively small proportion of the exposed geotextile surface. A much larger area (shaded white) was devoid of root penetrations. The tree planting pit was to the lower right of the image.
In seeking to refine the scope and methodology of the ‘National Trials Project', develop cost estimates and source funding opportunities, TREENET is engaging with key stakeholder groups in order to progress best practice in designing and maintaining engineered spaces for tree growth in paved areas in Australian cities.
Interest continues to be sought from research organisations, industry associations, product manufacturers/distributors, product user groups (eg. local government, landscape architects, urban designers, construction companies) and potential trial site stakeholders.
Check out the following resources which have been extracted from TREENET's significant collection of academic papers and case studies:
Trees in Hard Landscapes – Trees & Design Action Group (TDAG)
Examples of existing experiences can be explored via the Case Studies Portal.