A REPORT INTO TREE CANOPY COVER ACROSS HOBART

STATE OF THE CANOPY

STATE OF THE CANOPY: A Report into Tree Canopy Cover Across Hobart

INTRODUCTION 4

GROWING HOBART’S URBAN FOREST 6

EXISTING TREE PROTECTION FRAMEWORK 10

HOW DO WE GROW TREE CANOPY COVER ON PRIVATE LAND? 12

STATE OF THE CANOPY: A Report into Tree Canopy Cover Across Hobart A Report into Tree Canopy Cover Across Hobart – 2023

However, if you take Hobart’s surrounding bushland reserves out of the equation, and only look at canopy cover across the city’s urban landscape, the picture is very different.

Cities often measure their health in terms of ‘green infrastructure’. This can be calculated, in large part, by the percentage of land covered by tree canopy. A city’s tree canopy is made up of trees planted right across a city, and includes trees on private property, along streets, in parks and surrounding nature reserves. Hobart is unique among capital cities across Australia.

This report measures Hobart’s canopy cover across just urban areas, excluding forested bushland reserves and rural living zones. We want to get a better understanding of the tree canopy cover within Hobart’s urban areas – the places where people live, work and spend their day-to-day lives. This canopy mapping was undertaken by Geoneon.

The City of Hobart has an ambitious target of increasing tree canopy cover across its urban areas to 40 per cent by 2046. This new data, which uses planning zones to map tree canopy suburb by suburb, provides the information we need to target those areas most in need of more tree canopy through new tree plantings to reach our ambitious 2046 goal.

2046 GOAL

Increase Hobart’s urban tree canopy by 40% to 40%.

GROWING HOBART’S URBAN FOREST

While the entire Hobart municipality has the highest tree canopy cover of any capital city in Australia, at 59 per cent, it contracts significantly when we look at canopy cover for just our urban areas.

In 2017, as part of the City of Hobart’s Street Tree Strategy, Hobart’s urban canopy cover was calculated at 16.9 per cent. However, new canopy mapping using a clearly defined urban area and satellite imagery from spring and summer of 2017 and 2022 reveals a different picture.

The new canopy mapping was conducted by Geoneon on behalf of the City of Hobart. Geoneon uses satellite data, artificial intelligence, and data fusion to leverage spatial data that makes cities more efficient and sustainable. Its tools help cities improve land-use and infrastructure planning.

BOUNDARIES – URBAN & NON-URBAN

The new canopy mapping has been undertaken using clearly defined urban areas based on local land use zones that reflect urban uses:

• general residential
• inner residential
• low density residential
• urban mixed use
• commercial
• central business.

Satellite imagery from 2017 and 2022 was used to compare canopy cover across Hobart’s urban area over a five-year period, covering all 17 Hobart suburbs. The new data also reveals that tree coverage across Hobart’s urban areas went backwards between 2017 and 2022, with the city losing two per cent of its entire urban tree canopy. All of this tree canopy loss occurred on private land.

The Geoneon analysis used a trained deep learning model to perform tree canopy segmentation covering the designated area and reveals changes in tree canopy between 2017 and 2022 classified by:

• public and private land
• suburb
• land use zones

The change in urban canopy cover across public and private land within the City of Hobart between 2017 and 2022 is shown in figures.

KEY FINDINGS

Key findings from this analysis are:

• Canopy cover across Hobart’s urban areas in 2022 is 29 per cent.
• The canopy cover across Hobart’s urban areas in 2017 (using the newly-defined urban areas) was 31 per cent.
• North Hobart’s canopy cover has declined from 10 per cent to 9 per cent.
• Canopy cover has declined in urban areas by 2 per cent since 2017. All of the canopy loss occurred on private land.
• The suburb of Hobart has the lowest canopy cover across the Hobart municipality at just 6.9 per cent. This is a slight increase from 6.8 per cent in 2017, likely attributable to growth of existing canopy, protection of existing trees and the City of Hobart’s street tree planting program.

CANOPY CHANGE

Urban Private Land

The table shows change in urban canopy cover between 2017 and 2022 on both public and private land.

Hobart’s CBD area is the worst in terms of canopy cover – just 4 per cent of the central business zone is covered by tree canopy, despite the fact this is the area in which the highest number of workers and visitors spend time in Hobart.

In just five years – 2017 to 2022 – Hobart has lost two per cent of tree canopy on private land. This is equivalent to losing more than 27 MCGs worth of trees across Hobart. Assuming the average canopy for every tree lost is 10 metres wide, this represents the loss of 6875 trees on private land in just five years. Tree canopy cover on public land in Hobart has remained roughly stable, with a slight gain of 0.1 hectares between 2017 and 2022.

TREE CANOPY COVERAGE ACROSS HOBART

TREE CANOPY COVER BY SUBURB

Tree canopy cover by land use and suburb.

EXISTING TREE PROTECTION FRAMEWORK

The investigation of tree canopy cover across Hobart between 2017 and 2022 does not determine why there has been a loss of trees on private land. However, canopy loss on private land is generally attributed to:

• subdivision of larger blocks resulting in backyards being turned into housing
• larger houses and ancillary buildings resulting in less space for tree growth
• community attitudes towards trees (a negative perception of trees resulting in tree removal).

Councils often face the seemingly competing objectives of increasing the amount of available housing and diversity while increasing tree canopy cover. However, healthy and abundant urban tree canopy will be critical for the health of current and future populations.

TREES ON PUBLIC LAND

Under section 23 of the Public Spaces By-Law No. 4 2018 it is an offence to cut, prune, pluck, destroy, remove or injure any tree growing in a public space unless authorized to do so by a permit.

• Includes the Soldiers Memorial Avenue listing that contains 537 individual trees.

The Significant Tree Code includes trees across Council owned and managed land as well as private land, crown land, etc. Of the 1177 Significant Trees on the register (as of June 2023), just 25 per cent are on privately-owned land.

TREES ON PRIVATE LAND

The main existing mechanism to protect private trees in urban areas is the Significant Tree Code. However, due to challenges like increasing regulation on private land, it is recommended that the City of Hobart initially focus efforts on community education, tree planting incentives, and further research.

HOW DO WE GROW TREE CANOPY COVER ON PRIVATE LAND?

The new tree canopy mapping shows that the City of Hobart’s existing tree protection provisions on public land are working. To increase canopy cover on private land, the City of Hobart takes a multi-pronged approach that avoids greater regulation. These approaches include:

• Run tree giveaway events with stock sourced from the City of Hobart nursery.
• Provide small grants to individuals or groups wanting to enhance greening on private property.
• Provide small grants for individuals to maintain existing, large and important canopy trees.

THE BEST TIME TO PLANT A TREE WAS 20 YEARS AGO.

THE SECOND BEST TIME IS NOW.