JUST one in ten street trees in Ardross will be alive in 20 years because they’re ageing, reaching the limits of their climate change tolerance and lack diversity, a report has found.
Melville city council this week adopted the first action plan as part of its urban forest policy, concentrating on trees in the public realm. Although it controls 37 per cent of the land within its borders, the council provides almost half the tree cover; and that’s likely to increase as infill clears suburban backyards.
A report to this week’s council meeting said the city has been managing its tree and under-storey canopy well, but emerging risks could derail its plans to maintain existing cover and boost it in concrete-heavy areas.
“A survey of approximately 20,000 street trees indicates that more than 50 per cent of the city’s existing street trees may have a remaining useful life expectancy of less than 20 years,” the report said.
“In some suburbs this proportion is much higher.”
The report says many of the mature trees were planted in the 1950s and 60s when there was more plentiful rainfall and lower average temperatures.
“Critically, for urban forest management, the Bureau of Meteorology predicts that rainfall will decline by a further 15 per cent by 2030 (compared with 2011) and by around 30 per cent by 2090 (medium scenario).
“This time horizon is within the life span of trees planted now.”
The report says this may affect the health of trees, making them more vulnerable to attack by pests and diseases. Because more than 40 per cent of the city’s trees are either Jacarandas, brush box, peppermints or the Kings Park callistemon, it also makes them vulnerable to a wide epidemic.
About 250,000 trees will have to be replaced in the next 20 years, which will cost $11.25m at the current rate of $450 per juvenile tree.
That’s $562,500 a year, while the council currently budgets $270,000.