What does it mean?
The CSIRO defines urban greening as “vegetation that provides environmental, economic and social benefits”. Urban greening is the opposite of ‘urban greying’: “While ‘grey’ infrastructure has traditionally been the main focus of urban development and management activities, ‘green’ infrastructure is increasingly considered a vital asset for liveable, sustainable and resilient cities.” Essentially, urban greening means reducing the clearing of green spaces and introducing more green spaces to the urban environment.
What are the challenges for WA?
Almost 80% of all Western Australians live in the state’s capital city – that’s 1.98 million out of our 2.76 million people residing in Perth! This urban focus has of course meant land use shifting from the natural environment to the built environment. Despite revegetation efforts, the natural environment is diminishing within urban areas. Perth sprawls across one of the longest metropolitan regions in the world – from Two Rocks to Dawesville, and suburbs keep coming. New suburbs are critically lacking in green space, and although older suburbs often have more trees, they’re usually lacking native vegetation. Combined, this lack of urban green space is raising the temperature of the city significantly and removing critical food and shelter habitats for Perth’s native wildlife.
Maintaining and expanding Perth’s urban tree canopy becomes increasingly important as temperatures rise, air quality deteriorates, and the suburban sprawl expands. Perth’s tree canopy coverage varies greatly from area to area, but only covered 19.95% in 2016 (from the Greener Spaces Better Places “Where should all the trees go?” (2017)
). Therefore, much can be done by both state and local governments to increase the urban forest on public land and protect trees on private land.
Why is it important to act now?
Circumventing the urban heat island effect is very relevant in Perth – our summers reach high temperatures, and there are many hard surfaces. The Greener Spaces Better Places report “Where Will All the Trees Be?” (2020) has shown that “Between 2016-2020, 73% of [LGAs in Australia] increased their hard surfaces, or grey cover.”
WA is the only state in Australia that does not have legislation to protect trees or a Tree Protection Act – and right now there is not much protection for tree retention in building projects and on private properties.
In a more positive light, the CSIRO’s list of benefits of urban greening includes air and water purification, temperature regulation, food provision, recreation space and the prevention of environmental loss and degradation. One study also found a correlation between increased urban greenery and enhanced emotional wellbeing for those accessing and utilising these spaces.
Political ecologist Heather Alberro explains these potent benefits in The Conversation: “Plants can help cool cities through the water that evaporates from their leaves when exposed to the sun’s rays, and by shading surfaces that otherwise might have absorbed heat. Research has found that on a sunny day, a single healthy tree can have the cooling power of more than ten air-conditioning units.”
What action is being taken?
In Western Australia, the Liveable Neighbourhoods Policy guides the development of the built environment – however, it provides limited direction for urban greening. Local governments can and do incorporate urban greening in their Local Government Areas (LGAs) through collaboration with local stakeholders and partnerships with grassroots urban greening initiatives. A good example is the Town of Victoria Park, which uses urban forest strategies to increase tree canopy coverage within its district.
The WA Local Government Association (WALGA) has been instrumental in driving awareness on better urban greening. In 2018 they released the “Better Urban Forest Planning” document to help LGAs find their pathways towards retaining, regenerating and restoring green infrastructure. WALGA also has an Urban Forest Working Group, which released an issues paper in May 2022. This acknowledges the on-going loss of tree canopy cover in the built environment. It states: “The purpose of this issues paper is to identify barriers to the retention and enhancement of canopy cover and vegetation in urban areas of Western Australia that are within the remit of Local Governments to address through their planning frameworks.”
To this end, many LGAs now have voluntary registers or inventories for significant trees. For example, City of Fremantle has a Significant Tree Register. Likewise, the City of Vincent has a Trees of Significance Inventory. Once a tree is on the list, both councils require approval to be granted before it can be removed. However, they do need community members to self-nominate trees and for them to be accepted as significant by the property owner where the tree exists.
The City of Mandurah has enacted Tree Preservation Areas in addition to its Significant Tree Register. This seems to offer stronger protection as it states:
“The City’s Tree Preservation Areas are part of our greening strategy to protect mature, native trees and the benefits they provide. This scheme is not limited to City-owned trees. Trees in your backyard are a key part of our environment and contribute to local biodiversity and our sense of place.”
Additionally, the State Government has provided $750,000 worth of grants to local councils under the Urban Canopy Grant Program 2021, funded by the Water Corporation and administered by WALGA. The goal was to plant 3,400 trees by 2022.
While great things are happening at a local level, many of these initiatives are not joined up with each other – and this means some suburbs prosper while others are slipping through the cracks. Urban greening-focused suburbs aren’t just prospering from their access to green space – their inhabitants are literally prospering as the shade afforded means the entire suburb can be a few degrees cooler than tree-less counterparts, and therefore less intensive air conditioning is required. We can generally expect a shaded street in Peppermint Grove or Highgate to be far cooler in mid-summer than tree-less street in surrounding suburbs. This inequity across the city is already severely impacting people’s standards of living, and during a cost-of-living crisis too.
What does good look like?
The city of Singapore is a great example of urban greening. Referred to as a garden city, the city incorporates greenery on building roofs, walls and balcony areas that mimic natural canopies. Singapore’s required floor plate ratio strategy has resulted in greenery covering at least the area of each building floor plate, and urban greening has become mandatory for building design and maintenance. This demonstrates how urban greening can succeed within a densely populated urban environment, utilising even tall buildings and the small spaces in-between them.
However, for this to be successful in WA’s unique and changing climate, specialist horticultural knowledge must be taken into account when selecting appropriate species and an on-going care and maintenance programme needs to be in place.
What action needs to be taken in WA?
Stronger action by LGAs, and the update of local planning schemes to include urban greening are an essential across LGAs. However, there needs to be stronger action taken through the State Planning Framework to ensure the amenity of urban forests and tree canopies are fully protected. Based on our consultation with local governments and other agencies, we recommend the following actions:
- Create a state Tree Protection Act to legislatively protect trees – the default should be keeping trees and removing them the exception.
- Implementing state-wide canopy cover minimum standards (% cover per sq KM)
- Deep root zone mandates for all new builds, plus design regulations to include existing trees when new houses and apartments are built
- Urban greening requirements to be considered in all planning development approvals including major ones
- Main Roads review of tree removal practices, plus requirements that existing mature trees must be accommodated when designing roads
- Offsetting the cost of maintaining trees on private land can be e.g. subsidised arborist services from LGAs, rate reduction to account for environmental services, regular leaf clearing and composting as part of road and verge maintenance
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