by Carla Caruso

More underplanting beneath big trees would help discourage activities directly under them and manage the level of risk in public reserves.

That’s according to Joanna Wells, who’s an outreach coordinator at the Conservation Council of SA and a councillor with the City of Mitcham.

Underplanting is a gardening technique where smaller plants are cultivated beneath larger ones. 

Mitcham Council put the technique into practise in Mitcham Reserve after a river red gum dropped a big branch there about 15 years ago. Fortunately, no one was hurt.

Joanna said: “Now, if you go back to that reserve, and have a look, you’ll notice that the area immediately under the [gum] trees have all been underplanted with endemic native species, and they’ve put wood-chips down.

“So, there’s a really clearly delineated area, where you wouldn’t put your picnic rug and have a picnic under the canopy of the trees. It’s a very sensible approach about managing the level of risk.

“[These gums] are really beautiful examples of how to manage the risk and how to live with the trees.

“The under-plantings actually release a whole lot of sugars and so on, which the trees then take up. So, it’s fantastic in terms of trees health. There are all sorts of benefits.”

Joanna believes more education is also needed around how people can live side-by-side with trees.

“If you can educate people about what the real risks are, why things are happening, and what they can do to avoid them, then you can actually shift the mindset.

“So [for example] you don’t go and sit under a gum tree on a really hot day or a really windy day because that’s when it’s more likely to drop a branch if it is under stress.

“Something we’d be keen to see as part of tree [protection] reforms is a really good education campaign about the benefits of trees.

“And obviously, if you’re going to do that, the flipside is to say that there is a level of risk. But it’s actually a lot smaller than what you think, and here’s how you can absolutely minimise it and get it down to close to nothing by not doing these things in these circumstances.”

Trees drop limbs only when they’re stressed, Joanna added.

“There’s a lot of reasons why they can be stressed, but mostly it’s about climate change.

“The other part of it’s that we’ve taken out significant amounts of our urban forest. When trees grow, they develop their root system in such a way that they’re actually stabilising themselves against the prevailing wind.

“And that’s in conjunction with all the trees around them, because the other trees around them actually protect them.

“So, if you take out all the trees around, and you leave one tree in isolation, it doesn’t have the protection of the forest anymore. So, it’s more vulnerable.

“The other thing is that under climate change, wind directions have actually changed. And you might have a big tree and it’s grown, because the prevailing wind is from the southwest, and suddenly the winds are changing, and the wind direction is now from the east or the south-east.

“Because it’s not stabilised to face it coming from that opposite direction, and the roots have grown out that way to protect it from that wind, when it comes from another direction, that can actually be enough to blow it over.”

Last month, Independent MP Frank Pangallo called on Councils and the State Government to cut back ageing gum trees overhanging major Adelaide roads.

His call followed multiple incidents across the State in which large limbs had fallen – including one that tragically killed 22-year-old Indonesian university student Alifia Soeryo in Bullrush Park / Warnpangga (Park 10).

However, Joanna said that Pangallo’s call was “absolutely not the track” she would support.

“[One] concern about removing trees or pruning them significantly on main roads is that we actually need that canopy to cool the streets, so that people can walk and ride and use active transport rather than saying, ‘It’s too hot, I need to get the car.’

“Roadside trees can [also] actually slow drivers down because you have to be a little bit aware – whereas a dead straight road, when you’re traveling at 100km/h, that’s actually, in a lot of ways, riskier.”

As well, she said there are other benefits for people’s health and wellbeing. “There are statistics that show that if you have canopy within 1.6km of your home, you’re 30 per cent less likely to suffer from mental health problems like stress and anxiety.

“Then there’s further evidence that shows that, if you’ve got that canopy within that same distance of your home, you’re 30 per cent less likely to develop health that’s in the poor to fair range.

“So, when you think about the mental health problems that are just rampant right across society and the health problems that we’re seeing, [trees are] actually a really good investment in the health budget.

Joanna pointed to a new publication, compiled by Ann Doolette, which further busts some of the more common tree myths – all based on scientific evidence – to encourage homeowners and government agencies to preserve trees. 

Meanwhile, to get involved with Conservation SA’s Protect our Trees campaign, head to www.conservationsa.org.au/trees.