Almost four in every ten trees found in Melbourne’s streets, parks and natural landscapes are vulnerable to climate change, a report has found.
Conducted by the University of Melbourne in conjunction with the City of Melbourne, the Future Urban Forest report found that 35 percent of all trees planted within the city’s parks and urban forests and 48 percent of all species of trees planted were either moderately or extremely vulnerable to climate change under a moderate scenario which under which temperatures are presumed to increase by 0.8 percent between now and 2040.
Species from colder or narrow climates in northern Europe or the north-eastern United States such as the Dutch Elm were particularly vulnerable, the report said.
Also vulnerable were species from narrow climates, such as many locally indigenous and other native trees including many species of Eucalypt and Acacia trees.
By contrast, it said that trees which have been identified as suitable for Melbourne’s climate include the sub-tropical South American Jacaranda (Jacaranda mimosifolia), the Australian native evergreen Brush Box (Lophostemon confertus) and the indigenous Coast Banksia (Banksia integrifolia).
According to the report, the vulnerability of the two aforementioned groups presents a particular challenge as both groups were critical to the city from the viewpoint of biodiversity, liveability and cultural identity.
Whilst these species will become less reliable in the future, the report says they still could be viable in some places with suitable management strategies such as irrigation and improved soil conditions.
In addition, more activity will likely be required in areas such as tree removal, pruning and planting in response to damage, decline and mortality, the report said.
Whilst there were hundreds of species that were potentially suitable for planting instead, the report suggests that this area presents further challenges.
Extra processes will need to be developed in order to test and select species in order to determine their suitability, it says.
In order to limit the risk of unsuccessful plantings within larger streetscapes, formal street tree trials will initially need to be limited to smaller areas, it adds.
Liaison with the nursery industry in purchasing plants of the future will also be essential, as will testing any new species for weediness.
Finally, it is critical to maintain or enhance diversity when undergoing tree selections in order to provide a healthy urban forest, the report says.
Melbourne Lord Mayor Robert Doyle said the research will be used to make evidence based decisions about which trees should be planted in order to safeguard the city’s urban forest future.
“Trees are a defining part of Melbourne but they are also vulnerable to the effects of climate change,” Doyle said.
“Past experience of drought, including the Black Saturday period in 2009, has shown us that we need to plant new Australian and international species that are suited to warmer temperatures.”
The latest report comes as the City of Melbourne is undergoing an urban forestation strategy which is designed to increase tree cover from almost 25 percent now to 40 percent by 2040.
There are currently around 77,000 trees in Melbourne’s streets, parks and urban forests, and the city is planting around 3,000 trees per year at a cost of $1.5 million.