Victoria Park, Australia

Photo by: Pierre Quesnel

Sustainability and Resilience

What efforts have been made to reduce the carbon footprint of the initiative?

Street trees planted to our new specifications receive half the amount of water to reach establishment as those planted under previous methods. Other bushland restoration techniques have also been employed within an urban context: dry planting, large scale soil amelioration, site preparation and ongoing maintenance programs. These techniques are vital to enable mass urban greening that’s sustainable and achievable without intensive resource use.

Trees and shrubs propagated at a nursery located on the immediate boundary of the Town reduces travel time – and hence car / transport pollution – for staff and contractors picking up and planting the stock.

Trees in urban environments often don’t reach their full size & health due to the restrictive root zones they’re planted in, staying in an immature state for many years (or their whole lifetime). The Town is addressing this issue by providing adequate soil volume for urban trees to reach maturity. This is a win-win situation, providing hard paving for pedestrians above the root zone while delivering uncompacted soil for the roots to survive in.

Permeable paving allows rainwater to infiltrate the paved areas and enter the root zone. 14 x 8m2 zones are created in a high street urban area to improve tree health and speed to reach maturity as well as improve drainage and urban water outcomes.

Given the vast amounts of trees and shrubs planted yearly, the program has a net positive impact on climate change mitigation and on adaptation through cooling the urban environment.

How have the anticipated impacts of climate change been considered?

Western Australia has a long history of using exotic trees in streetscapes and urban areas. Its impact are starting to be noticed with water table reductions, increased summer heat and lower rainfall in the last few decades. Accustomed to cooler climates and higher rainfall, some exotic species are in poor health due to their lack of climate suitability.

Our Urban Forest Program has focused on a shift in tree planting species towards climate suitable exotics and local tree species. In a sign of great change, the 5 most planted species in the 2021 street tree planting program were native species. This move towards native trees increases the ecological services provided by the tree plantings, fostering the ancient relationships between local flora and fauna.

Included in our aerial mapping analysis is highly detailed thermal mapping of the Town. This data is used to determine “hot spots” in Town – areas of higher risk of heat wave related deaths now and in the future. These areas are compared with vulnerability demographic data to determine areas of focus for tree planting. A Number of High Urban Heat and High Vulnerability have been recognised near aged care housing providers and in low socio-economic areas with tree planting targeting these areas. It was also determined that overall Carlisle and Lathlain were the two overall highest temperature suburbs within the Town. Tree planting has targeted these suburbs. This data based targeted approach will assist in climate change adaptation for the Town, now and into the future.

What processes does the initiative include for it to be considerate in its use of soils and other natural resources?

The Urban Forest program implementation has included the reduction in irrigated turf around the Town and replacement with Urban Ecosystem areas that are unirrigated. This has led to a reduction of Town water use in Parks and high-profile verge spaces. This active process of turning non active turf spaces into urban ecosystem sites increases fauna habitat, protects biodiversity, reduces fertiliser usage and reduces irrigation to protect potable water sources.

In addition these urban ecosystem areas have developed working on using the natural soil existing on site rather than imported soils. Compost is used during planting to improve soil quality and organic mulch from certified sustainable and pathogen free sources is used in great abundance. This specialist timber industry by product mulch retains soil moisture and slowly breaks down releasing organic material into the local soils. This moisture retention and organic material helps bring the soils to life building an ecosystem in the soils of beneficial microbes.

Street tree planting has researched and adopted new specifications that have led to a halving of the amount of water used to bring a tree to establishment. These techniques include, smaller stock sizing (25/35L), existing soil amelioration with Terracottem products and use of large tree wells.