New data shows that while canopy cover is declining in the leafier eastern areas of Sydney, it’s increased slightly in others. As of 2022, tree canopy cover across Greater Sydney was 21.7 per cent, a slight increase from the 21 per cent measured in 2019. But there are some significant variations in different parts of the city.
Canopy gains
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More than half (18) of the 33 councils in Greater Sydney areas saw an increase in tree canopy cover between 2019 and 2022, though the increase varied dramatically (Figure 1). Some, like Blacktown and Liverpool in Sydney’s west, with some of the lowest canopy cover of any council, saw some of the greatest increases.
Canopy coverage in Blacktown increased from just over 12 per cent to more than 17 per cent between 2019 and 2022. This is a significant increase of 1166 hectares in tree canopy area and reflects investment in tree planting and maintenance by the NSW Government, council and the community.
Canopy losses
Further to the east, there have been declines in tree canopy cover in many of Greater Sydney’s leafier council areas. In fact, every council (except Mosman) with 30 per cent or more canopy cover in 2019 experienced canopy loss by 2022.
The highest losses are in Ku Ring Gai (loss of 8.2 per cent, 610 ha), Northern Beaches (loss of 5.2 per cent, 665 ha), Sutherland Shire (loss of 8.83 per cent, 969 ha) and Wollondilly (loss of 5.91 per cent, 471 ha). While these councils are already closest to the 40 per cent target for Greater Sydney, this data shows a trend away from the target rather than towards it.
Tree canopy across Greater Sydney– where are we on the road to 40 per cent cover?
As we move through this summer and hit our hottest months (predicted by the Bureau of Meteorology to be unusually hot, driven by a strong El Nino event), preparing for and adapting to hot conditions in our cities becomes more apparent.
Urban trees are one of the most effective ways of reducing temperatures, improving human thermal comfort in urban areas, and providing a range of other benefits. The NSW Government has a target to achieve 40 per cent tree canopy cover across Greater Sydney to provide shade, cool the air and help protect the community from extreme heat.
Several major initiatives are underway by the NSW government to support the achievement of the target, including the publication of the Greener Neighbourhoods Guide, the Greening Our City Program and most recently, tree canopy data across the Greater Sydney area, released in early November 2023.
The new data set shows tree canopy cover across the city from a bird’s eye view and is calculated as a percentage cover over an area (for example, a council, a park or residential streets). Generated using aerial imagery captured and analysed by ArborCarbon, the canopy cover measurements are a state of the art environment data set that will change the game for people working in urban forestry, climate change adaptation, human health, urban heat, open space, urban nature and urban greening.
The NSW government has released some of the data to the public, and the highest resolution data is available to local governments to help them make informed and targeted decisions relating to urban sustainability and green infrastructure across Greater Sydney.
Mosaic Insights used some of the publicly available data to explore changes in tree canopy cover for the 33 councils in Greater Sydney since the last survey in 2019 and to start to understand the number of trees that need to be planted in each council to help Greater Sydney reach its 40 per cent target. You can explore the changes in our web map.
We’ve used this valuable data set to consider some of the big questions we face as we attempt to adapt to climate change and urban nature collapse.
As of 2022, tree canopy cover across Greater Sydney was 21.7 per cent, a slight increase from the 21 per cent canopy cover measured in 2019. But there are some significant variations in different parts of the city.
Canopy gains
More than half (18) of the 33 councils in Greater Sydney areas saw an increase in tree canopy cover between 2019 and 2022, though the increase varies dramatically (Figure 1). Some, like Blacktown and Liverpool in Sydney’s west, with some of the lowest canopy cover of any council, saw some of the greatest increases. Canopy coverage in Blacktown increased from just over 12 per cent to more than 17 per cent between 2019 and 2022. This is a significant increase of 1,166 hectares in tree canopy area and reflects investment in tree planting and maintenance by the NSW Government, council and the community.
Canopy losses
Further to the east, there have been declines in tree canopy cover in many of Greater Sydney’s leafier council areas. In fact, every council (except Mosman) with 30 per cent or more canopy cover in 2019 experienced canopy loss by 2022. The highest losses are in Ku Ring Gai (loss of 8.2 per cent, 610 ha), Northern Beaches (loss of 5.2 per cent, 665 ha), Sutherland Shire (loss of 8.83 per cent, 969 ha) and Wollondilly (loss of 5.91 per cent, 471 ha). While these councils are already closest to the 40 per cent target for Greater Sydney, this data shows a trend away from the target rather than towards it.
How many more trees and canopy areas do we need to reach 40 per cent?
We must plant more than 8 million new trees to meet the 40 per cent canopy cover target.
Despite the increases in canopy cover seen across many councils in the west, their low starting point means that many more trees are still needed to reach the 40 per cent target.
Councils that need the greatest increase in canopy area to reach 40 per cent cover are the larger councils in Sydney’s western and central city areas – Blacktown, Liverpool, Penrith, Campbelltown, Camden, Canterbury Bankstown, Cumberland, and Fairfield. While some of these areas have seen significant increases in canopy cover since 2019, they still need thousands of hectares of additional canopy to get close to 40 per cent overall canopy cover.
For example, the analysis shows that in Blacktown, nearly 4900 hectares of additional canopy cover is needed to reach 40 per cent overall canopy cover (Figure 2). For the purposes of the exercise, we made some assumptions that:
- the canopy of a typical tree has a diameter of 7.5 metres
- every new tree survives to maturity, and the existing canopy is retained or replaced (i.e. we have not modelled the growth of juvenile trees or the reduction in the canopy as trees reach the end of their lifespans)
Based on these assumptions, more than 1.1 million new trees are needed in Blacktown alone, and nearly 8.5 million new trees are needed to reach 40 per cent canopy cover in every council in Greater Sydney.
Have we got tree canopy cover in the areas we need, and have tree planting activities helped?
While canopy cover has significantly increased in parts of western Sydney, where more vulnerable communities live, we are still a long way off the target. Where do we find space and funding for the 8.5 million more trees?
The NSW government’s Greening Our City program has supported this canopy growth over the past four years through giveaways, targeted tree planting and partnerships with local government, the community, the NGO and the private sector.
The program aims to plant up to 5 million trees by 2030, so it is not far off the mark, but how will it get there?
It may seem obvious that one of the barriers to delivery will be costs. While planting 8.5 million trees will come with a hefty price tag, research suggests that it is not the resourcing that is the biggest challenge. Considering that the cost is dispersed across 33 council areas, between local government, state government, private sector developers and individual households, it is not a lack of dollars that poses the biggest barrier.
The current barriers to planting trees that will provide future significant tree canopy are:
- space
- skills and influence
- sentiment
Space and the lagging planning and development controls to support the canopy are major barriers to canopy growth. A substantial tree canopy needs space above the ground and below the ground. Mosaic Insights recently completed canopy modelling on a business as usual approach to greenfield development in a western Sydney LGA.
Based on the current planning and development controls (which include a desire to reach the 40 per cent canopy), the development site would only reach a canopy of less than 20 per cent. To reach the 40 per cent target, the public domain and private lots need to be radically reconsidered. Changes to local streets and major roadways, traffic management, stormwater management, open space, residential lot sizes, and urban forms are critical to accommodate larger canopies.
Space is equally critical in older suburbs, especially in those leafier areas of the city going through an infill boom and experiencing the greatest canopy loss. Local government needs support and integrated planning and delivery to consider the space required to establish and maintain large canopy trees.
Skills – there is a significant lack of capacity and knowledge about trees in urban settings across the industry. In many cases, staff with horticultural or aboricultural skills are lacking in local and state government roles, and if they do exist, they are often not in senior roles with influence over decisions that impact canopy and in senior decision making roles.
When it comes to conflicts between green and grey infrastructure the green gives, we have seen this at local and state levels with significant tree loss to make way for infrastructure.
Sentiment and the attitudes and beliefs of the community are significant challenges and barriers to better decisions around tree management.
Attitudes towards trees across the city point to a community unaware of the need for trees and the significant role they play in human health and wellbeing, providing ecosystem services and support for economic prosperity.
Grassroots campaigns in local governments across Sydney are making a difference; however, most councils defer to the wishes of individuals when it comes to public street tree plantings, a shift that has come with the rise of community consultation and the Have Your Say momentum. As a result, trees in the public domain are patchy (there are many vacant spots where trees could be planted), and individuals often determine species selection.
How much will it cost?
The cost of planting the number of trees needed to reach 40 per cent could be up to $5.9 billion.
The analysis we’ve presented illustrates the scale of the challenge in achieving a 40 per cent canopy in terms of the number of trees needed, but the financial cost is likely equally significant. In a recent study for Living Melbourne, Mosaic Insights and Natural Capital Economics analysed the costs and benefits of planting trees across large areas of Greater Melbourne identified as high priority areas for urban heat reduction. Using a simplified version of the cost estimate approach from that study, we estimated the cost of establishing the number of trees needed to meet the 40 per cent target to be around $5.9 billion.
If the total lifecycle cost of the trees – which includes the establishment, maintenance throughout their lifespan and removal – is accounted for, the cost would be more than $15 billion.
However, these costs are based on state and local governments planting trees on public lands, such as streets and plazas. Alternatively, approaches are likely to be significantly lower in cost, such as promoting planting on private land, funded plant giveaways, etc (although the success rate of some of these initiatives is uncertain).
How realistic is the 40 per cent tree canopy cover target, and how can this data help identify a more nuanced approach to canopy cover target setting?
Reaching 40 per cent across Greater Sydney is a challenging but worthwhile target.
The number (and cost) of trees needed to achieve 40 per cent canopy cover in all the councils in Greater Sydney is significant. But it is important to remember that the value of the benefits of achieving this would be greater. Our benefit/cost analysis for greening Greater Melbourne clearly showed that the investment stacks up: for every $1 investment in greening, the benefits returned to the community, business and governments across metropolitan Melbourne is around $4 (with a range between a return of $2.16 and $6.70 for every $1 invested). A comparable return would likely be found in Greater Sydney.
Is 40 per cent the right target, or should it be more nuanced? If so, how can this analysis guide its nuance?
The target is ambitious and, if achieved, will lead to a cooler, more resilient city. The new data can assist at the city, LGA, and site/lot scales.
All councils have access to this data, and we recommend using this information to drive strategic decisions around public and private tree management.
This data can help councils understand:
- where their LGA sits with total canopy cover
- where canopy losses (or gains) have occurred (land types, suburb types)
- opportunities and risks for future canopy when combined with public tree inventory data – specific information gained from tree inventory work provides information about vacant sites, age of trees, useful life expectancy, species diversity and climate resilience and risk management approaches.
- where a canopy is needed to support active lifestyles, active transport, and more liveable neighbourhoods, e.g. for some walking and cycling routes, a canopy of 90 per cent may be more desirable.
It is clear from the analysis that:
- the priority for new tree planting should be in the western Sydney councils, which have the lowest canopy cover and the most vulnerable populations. Many of these councils are heading in the right direction with increasing canopy, but they are still much lower than other areas in the city
- canopy losses need to be stemmed and reversed in areas with a downward trajectory in canopy cover – particularly in the eastern suburbs. The first step is to understand the drivers and spatial patterns of canopy loss in more detail and then address the causes of the loss in the tree canopy. The NSW Government published the Greener Neighbourhoods Guide (prepared by treeIQ and Mosaic Insights which supports NSW councils and their communities to develop strategies and plans that will achieve this
Disclaimer: Mosaic Insights is a strategy, planning and design consultancy whose clients include state, federal and local government, and private sector businesses.
