With bushfire season coming early this year, some homeowners might be tempted to rip the big old trees from their backyards.
But a veteran arborist is advising that some canopies may actually help shield us from danger.
NSW arborist Jill Boyes, 63, knows she might be acting against her best financial interests, but after 45 years of experience, much of it cleaning up after bushfires, she wants Australians to think differently about trees.
“Ember attack is what takes most properties out – houses and everything else, it’s the most dangerous thing in relation to assets on the ground,” she said.
Ms Boyes says that while trees with oil rich leaves can quickly catch fire, some large species, especially those with a high moisture content, will actually shield houses from falling embers.
She believes the large, wide crowns of some trees can act as an umbrella, catching and extinguishing embers before they settle on roofs and yards and ignite debris.
“There are parts of Australia where there are tree species which are highly resistant to crown fires,” she said.
“That is to say, there are many species where you could put a blow torch to the canopy and they wouldn’t go up.”
Local knowledge is key
Australia’s forests vary dramatically, so there are no hard and fast rules to follow in terms of which species prevent bushfires in different areas.
Ms Boyes encourages Australians to talk to the old guys at their local fire station in order to gain knowledge about a specific region.
“Some of the best people to get information from are often not the academics, but the people who have been fighting fires for ages,” she said.
“They know what burns and what doesn’t.
“Captains of local bushfire brigades and people like that, they’ve got the local knowledge.”
‘Magical list of plants’
Mark Hawkins, Development Planning and Policy Officer at the Rural Fire Service, told Yahoo News Australia that there wasn’t a “magical list of plants” that helped prevent fire.
“You can get a rather innocuous plant like the Mount Morgan silver wattle, it hasn’t got a huge distribution in Victoria, but if you put that plant in NSW it will go bananas because it’s warmer,” he said.
“So, it will actually spread like crazy and that plant then will increase the fuel load.”
Mr Hawkins advised that it’s the configuration of trees and plants that is important.
“You might have seen a long line of trees on a rural properties – that’s called a wind row,” he said.
“An ember can travel for kilometres and if it hits that vegetation it can then be deflected or stopped.”
The important thing is to ensure that if the ember then falls, it doesn’t land in undergrowth which could catch alight and send flames up the tree.
Preparing your yard
Jon Gaibor, Environment and Hazard Services Supervisor at the Rural Fire Service, told Yahoo News Australia that it was the undergrowth that posed the greatest risk in most fire situations.
“As a first point of call when you’re looking at removing vegetation from a property, the trees are generally some of the last things you might look at,” he said.
“Residents should go about removing the lower level of plants and then assess the risks associated with larger trees.”
The major threats in extreme conditions
Ember attacks are not the only type of fire though, and in extreme conditions, such as those experienced during Black Saturday almost10 years ago, the tops of trees did catch fire.
Mr Gaibor said that once the canopy catches fire, all trees become a hazard.
“If they’ve got connectivity at a canopy level to the bush, and you get those really extreme conditions when the fire is in the crown, then that’s going to be a pathway for the fire to your property,” he said.
“The guiding principle is don’t have plants that can contribute to direct flame contact or direct radiant heat to your house.
“If you’ve got vegetation within 10 metres then it definitely could end up contributing to direct flame or radiant heat, and beyond that it depends on what type of plants you’ve got.”
While there are many grey areas in fire risk management, Mr Gaibor’s key recommendations are:
Have a 10 metre separation between a house and plants.
Create an asset protection zone around the home of between 20 and 40 metres.
Have no more than 15 per cent canopy cover within 50 metres of an asset.
Keep vegetation within islands of around five square metres in the outer parts of your garden.
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