Published on 12 August 2024
Trees for the future – a big win
A project to build the long-term resilience of Adelaide’s urban forests has garnered a major award in the 2024 SA Climate Leaders Awards.
The Future Trees Climate and Biosecurity Vulnerability Benchmarking Study won the research award for analysing more than 600,000 trees across greater Adelaide and identifying how they are vulnerable to a changing climate, diseases and pests.
The study used data from 20 councils, including the City of Onkaparinga, to map which types of trees are planted across greater Adelaide.
It found that there is a reliance on a small number of tree species, making our streets and reserves vulnerable to climate and biosecurity threats.
“Thirteen species make up more than half of all trees across greater Adelaide,” says co-leader of the project Dr Stefan Caddy-Retalic, Regional Coordinator of Resilient South and researcher at the University of Adelaide.
“Some of the most abundant species are from subtropical or temperate climates – jacarandas, Norfolk Island pines, Queensland box, plane trees and ornamental pears.
“They’re growing well enough in Adelaide for now, but they’re vulnerable to the hotter and drier conditions we’re seeing with climate change and the longer and more intense droughts and heatwaves that are coming.
“There are also biosecurity threats that have arrived in Australia and are likely to reach Adelaide. These will affect both exotic and native trees.”
He names, for example, myrtle rust, a South American fungus that is likely to impact eucalypts, and polyphagus shot-hole borer, a southeast Asian beetle that ‘farms’ fungus inside trees as a food source and has recently led to the removal of hundreds of trees in Perth.
To make Adelaide’s urban forests less vulnerable to both climate and biosecurity threats, the study recommends increasing the variety of tree species planting across Adelaide and selecting trees that are better adapted to arid conditions.
“By moving away from planting single species along avenues and roads, instead planting a mixed variety of trees, we decrease the risk of mass loss of trees,” says Stefan.
“By choosing trees for more arid conditions, we are getting ready for a hotter and drier future.
“You might assume that choosing trees that are native to the Adelaide region is the ideal way to go. Certainly, they’re best adapted to the environment we currently have.
“But that environment is changing and we want trees that will remain healthy for decades. We have to choose trees that can survive and thrive in the climate we’ll have in 80 years from now.
“This means looking at trees from more arid parts of Australia or overseas.”
The study was conducted by the University of Adelaide in partnership with Resilient South and was co-led by Stefan and Dr Kate Delaporte from the university’s Waite Arboretum.
Resilient South, a partnership between the South Australian government and the Cities of Onkaparinga, Holdfast Bay, Marion and Mitcham – contributed Stefan’s time.
“Phase 1, the benchmarking study, identified the scale of the problem,” said Stefan.
“We are now seeking funding for phase 2 to trial and implement the solutions, such as trialling new species of trees, working with nurseries to develop new cultivars here in Adelaide, and planting thousands of trees across urban areas.”
Nina Keath, Team Leader Sustainability at the City of Onkaparinga, says the value of the project for Onkaparinga is clear.
“We have made ambitious commitments to increase our urban tree canopy and we want to make sure our significant investment in tree planting is underpinned by the best evidence,” she says.
“It’s critical that our urban forest is designed for the future and not just the present, that it can withstand climate change and emerging disease and pests.”
Onkaparinga’s tree canopy increased by four per cent from 2018 to 2022 to around 20 per cent coverage.
The council has planted more than 56,000 trees on street verges, alongside waterways and in parks since 2017 in its quest to plant 100,000 trees by 2037 to continue to increase the overall canopy.
The SA Climate Leaders Awards are held every two years. The awards, an initiative of the Premier’s Climate Change Council, recognise the achievements of individuals and organisations who take action to address climate change in South Australia.
Earlier in the year, the future trees study won the SA&NT Parks and Leisure Association research award and is now one of three finalists for the national awards, to be announced in October.
The study’s success follows another win for a local greening initiative. Biodiversity McLaren Vale recently won the community partnerships award in the 2024 SA Landcare Awards for its collaborative efforts between the community, industry and government.
You can find out more about Onkaparinga’s tree programs, such as Adopt a Tree, Tree of the Month and planting targets at onkaparingacity.com/trees.