I’ve witnessed in my early career as a Registered Landscape Architect working across a commercial design studio, local government, and multi-disciplined design and engineering practice the disconnect between the popular blue sky thinking of many government agencies, and the day-to-day reality of urban development, particularly in relation to urban greening. These observations have been the catalyst for my research, and through a fellowship from the Landscape Foundation of Australia, I’m exploring how the current policies and systems can be improved to close the implementation gap and improve Sydney’s livability.

The role that urban green infrastructure such as urban tree canopy, parks and waterways play in supporting sustainable outcomes for cities is widely acknowledged. The benefits provided by nature in cities for people, the environment and economy; called ecosystem services, range from improved air and water quality to increased biodiversity, health and place benefits.²

Despite these targets and extensive tree planting programs/initiatives, canopy cover in more than half of Sydney suburbs is actually declining.^4,5

So why is this?

Research from RMIT suggests this decline in canopy cover stems from a combination of factors, including practices of private landowners, land and infrastructure development, and the age and health of existing trees.⁴ Concerningly, the same government departments that are setting these targets are simultaneously undermining them, through loose or contradictory policies and often their own capital works programs. The result is that trees are currently being removed at a faster rate than they can be planted and grown.

While legislation and policies are in place to protect existing vegetation such as the NSW biodiversity offset scheme, their efficacy in urban areas could be considered questionable. The triggers for such schemes are often too generous and exclude exotic or non-threatened native species which, in reality, make up a large proportion of the greenery in Sydney and urban areas in Australia.

This disconnects between best intentions and the realities of urban development, has seen urbanization recognized as the third largest threat to habitat loss globally. At home, a survey of Australian cities found that 30% of threatened species have distributions overlapping with cities. With some species relying exclusively on cities for their survival, while others depending on urban environments for crucial food and habitat resources.⁶

To counter this decline, the primary strategic focus has been on the planting of new trees, with retaining and protecting mature existing trees noticeably overlooked. This has unfortunately coincided with a focus on short-term urbanization goals, at the expense of long-term sustainable planning and place outcomes.

The lack of emphasis on retaining existing trees poses several problems. Firstly, trees take a considerable amount of time to grow, and establishing them in urbanized areas is challenging. They have the odds stacked against them and tree saplings don’t face the same growing conditions as their predecessors. They face numerous spatial and environmental obstacles, including limited sunlight due to taller and denser built form, competition with utilities and infrastructure, and unfortunately, deliberate acts of damage or theft.

The removal of these established trees becomes even more concerning when we consider the almost instantaneous loss of the ecosystem services they provide. By removing a large mature tree we lose both the human health and habitat benefits that tree provided, with the two tube stock trees planted as it’s replacement, unable to provide equivalent services for some time.

If we have any hope of achieving our urban canopy cover targets, we must first stop going backwards and halt the erosion of our existing green assets in cities.

What goes unmeasured often goes unvalued.

Historically, preventing the removal of urban canopy has been difficult because trees have not been recognized as financial assets by local and state governments. As a result they have not been recorded, monitored or maintained like other infrastructure assets such as roads or schools. This omission is problematic because it means nature isn’t accounted for in our decision and policy making; and with no real economic incentive or consequence for organizations or agencies to retain and protect existing green assets, concrete wins.⁷

These ‘green’ gaps in our policy and economic systems have resulted in under investment in our urban natural assets, enabling the gradual erosion of urban green infrastructure such as tree canopy.

Can urban natural capital accounting correct this trend?

The inclusion of nature in our economic system is not a new concept and momentum is growing to ‘mainstream biodiversity’ in government policy. In 2022 the Word Economic Forum’s Global Risks Report ranked biodiversity loss as one of the top three risks to humanity and there is an increasing awareness by governments and institutions of the dependency of our economy and GDP on nature and its services.^8,9

In urban areas natural assets are the network of natural and semi natural features in cities, including both green infrastructure and natural habitats and, much like grey infrastructure they provide services of value. Frameworks and metrics for natural capital accounting and assessment exist, however because natural capital accounting was first developed at a macro scale to measure whole country or regional environments, the frameworks and tools aren’t traditionally geared to measure the granularity and complexity of urban natural assets.²

Some cities such as London are beginning to adapt and create urban natural capital accounting tools to assess and monitor their assets to inform effective policy making.² Quantifying the value of urban green infrastructure such as street trees allows agencies to evaluate trade-offs, particularly when these come under pressures from urban development.⁶ Natural capital accounting can also monitor the health and condition of natural assets, ensuring governments prioritize the long-term management through sustained investment and maintenance.

The quicker Australian cities can adopt urban natural capital accounting the sooner we will see urban green infrastructure protected, invested in and maintained, to levels that allow cities to thrive in a warming world.

References

1. Historical population, 2016 | Australian Bureau of Statistics (abs.gov.au)
2. Natural Asset and Biodiversity Valuation in Cities : Technical Paper (English). Washington, D.C. : World Bank Group. http://documents.worldbank.org/curated/en/287521568801462241/Technical-Paper
3. Your say on our revised urban forest strategy – City of Sydney (nsw.gov.au)
4. Sydney urban forest cover drops across some councils since 2013 (smh.com.au)
5. Trees needed: Sydney’s councils lose tree canopy coverage | Architecture & Design (architectureanddesign.com.au)
6. H Kirk, G Garrard, T Croeser, A Backstrom, K Berthon, C, Joe Hurley, F Thomas, A Webb, S. Bekessy, Building biodiversity into the urban fabric: A case study in applying Biodiversity Sensitive Urban Design (BSUD), Urban Forestry & Urban Greening,Volume 62,2021
7. Demystifying Natural Capital and Biodiversity (kpmg.com)
8. Natural capital | NSW Environment and Heritage
9. Final Report – The Economics of Biodiversity: The Dasgupta Review – GOV.UK (www.gov.uk)

By Brittany Johnston, Senior Design Integrator, Aurecon