WHY CANOPY COVER TARGETS AREN’T WORKING TO GREEN OUR CITIES

Published: September 6, 2023Categories: Urban Design Policy & IntegrationTags:

Abstract

This article discusses why tree canopy targets are failing to green our cities and how natural capital accounting could help protect vital green infrastructure in urban environments. It throws light on the implementation shortcomings of government policies in this increasingly important area of urban planning and design.

About the Author

Sydney based landscape architect Brittany Johnston is working as a Senior Design Integrator at advisory, design and engineering company Aurecon. She is a National Advocacy Committee Member of the Australian Institute of Landscape Architects (AILA) and the 2023 Fellowship recipient from the Landscape Foundation of Australia. Contact: brittany.johnston@aurecongroup.com

Editor’s Preface

Brittany Johnston drives home the importance of implementation in policy making, with particular reference to greening the urban environment. Although focused on the local context where implementation is failing, the lessons are universal. By understanding the barriers to implementation in practice and moving in the direction the author argues for, we can create the preconditions for achieving the environmental outcomes we need in our cities and towns.   

Raeburn Chapman, Urban Design Review

Background

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.  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.

Declining Tree Cover

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.

Valuable urban tree canopy in Bourke Street, Sydney. Photo by: Greg Jackson, Urban Design, Roads and Waterways. Courtesy of: Transport for New South Wales.

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

So Why is This?

Research from the Royal Melbourne Institute of Technology (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. 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 pace than they can be planted and grown.

While legislation and policies are in place to protect existing vegetation such as the biodiversity offset scheme of the New South Wales State Government, 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 disconnect between best intensions and the realities of urban development has seen urbanisation recognised 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.

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 urbanisation 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 urbanised 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 the 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 canopy cover targets, we must 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 recognised as financial assets by local and states 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 organisations or agencies to retain and protect existing green assets, concrete wins.

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

In urban areas natural assets are the network of natural and semi natural features 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.

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.  Quantifying the value of urban green infrastructure such as street trees will allow agencies to evaluate trade-offs, particularly when these come under pressure from urban development. Natural capital accounting can also monitor the health and condition of natural assets, ensuring that governments prioritise 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.

Summary

State and local government policies aimed at increasing urban tree canopy cover need to go beyond ambitious targets and masterplan documents and be translated into practice.

Street canopy in Country New South Wales: Peter Street, Wagga. Such canopy needs to be protected in the first instance. Photo by: Greg Jackson, Urban Design, Roads and Waterways. Courtesy: Transport for New South Wales.

If we are to achieve stated targets, we need enforceable strategies to save our mature trees in the first instance so as not to take backwards steps before we even get started. We must limit own goals to something realistic in order to progress.  Furthermore, we should be actively accounting for nature in our policies and decision making, as cities like London and Toronto are beginning to do.

In doing all this we shift the collective understanding of the value of nature from abstract to tangible, and can work towards halting biodiversity loss while simultaneously greening our cities.

Acknowledgement

This article was originally published on Sourceable.net- on July 13, 2023 and with the author’s permission is re-published in Urban Design Review, with suitable changes.

References

Natural Asset and Biodiversity Valuation in Cities: Technical Paper (English). Washington, D.C. World Bank Group. http://documents.worldbank.org/curated/en/287521568801462241/TechnicalPaper.

Have your say on our revised urban forest strategy – City of Sydney (nsw.gov.au)

Sydney urban forest cover drops across some councils since 2013 (smh.com.au)

Trees needed: Sydney’s councils lose tree canopy coverage. Architecture & Design (architectureanddesign.com.au)

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

Demystifyng Natural Capital and Biodiversity (kpmg.com)

Natural capital. NSW Environment and Heritage

Final Report – The Economics of Biodiversity. The Dasgupta Review – GOV.UK(www.gov.uk)