Gum trees can reduce fire hazard

Following the unprecedented Australian wildfires in the spring and summer of 2019/2020 (some of which are still burning as I write) it is likely that some people will demand the clearing of gum trees to reduce the fuel available for future fires.

On this page I argue that, far from increasing fire hazard, gum trees can reduce it because they greatly reduce the amount of grass and other flammable material at ground level. I have made these observations on my own property near Clare, about 140 km north of Adelaide in South Australia.

I have observed at least four nearby bushfires, the closest of which came within a few hundred metres of my property (photos below), in the nearly 30 years that my wife and I have owned the place.

The ferocity of a fire depends on a number of factors, the amount of fuel available, where that fuel is (near ground level or in the tree-tops), how dry the fuel is, temperature, strength of the wind, and the humidity.

I make no pretence of being any sort of expert on wildfires.

This page was written 2020/01/18, last edited 2021/01/08
Contact: David K. Clarke – ©

Gum trees (Eucalyps) on my property near Clare, South Australia
Fire load
Note that there is much less grass near the base of the trees.
Photographed in January 2020

Anyone who has grown wine grapes in South Australia will tell you that vines are much weaker within 40 metres or so of established gum trees. It is the same with grass.

Closely planted gum trees will stop most grass from growing at all. Even scattered trees, as on most of my property, reduces the amount of grass, especially close to the tree. On the other hand, leaf litter can build up beneath the trees and produce its own fire-load.

More gum trees on my property near Clare
Fire load
Again, there is much less grass near the base of the trees.
Photographed in January 2020

Of course the trees themselves can burn if a fire is hot enough. Whether green leaves on a gum tree will burn in a bushfire depends on how much flammable grass, shrubbery or leaf-litter there is beneath the trees.

A fire in which the leaves on the trees burn is called a crown fire. I have not known a crown fire to occur in the Clare area, but they certainly do occur elsewhere in Australia.

In my area while some of the bark low on the tree will burn, the leaves very rarely have; they are usually killed by the heat of the fire and fall to the ground some weeks later.

Closely planted gum trees on my property
Fire load
There is practically no grass, but there is significant leaf-litter, beneath these trees. They were planted about 1995.
Photographed in January 2020

If there are many trees and there is little or no grass, or other flammable low-growth, beneath trees the trees will not catch fire and there is little else to burn.

We must keep sight of the core problem

Brooks Lookout, Clare, South Australia
Near Brooks Lookout
Photo date 2020/02/14
Brooks Lookout, Clare, South Australia
Brooks Lookout
Photo date 2020/02/14
The Australian fires of 2019/20, if not caused by climate change, were made far more likely to happen by climate change. We can expect many more fires such as these if we do not take climate change seriously in hand.

Government, public and media reactions to the fires concentrated on the fires themselves, recovering from the fires and compensating people and businesses for the damage they suffered from the fires. The fires were a symptom; the problem is climate change.

Even climate change is not the ultimate cause of the problem. We would have controlled climate change by now if not for selfishness, greed and apathy; collectively these are the first cause of the fires.

The photos on the right were taken 10 months after the area was burned in a bushfire that came within a few hundred metres of our property. Another fire a couple of years earlier came within two kilometres in a different direction.

I have ample reasons to be aware of changes in fire danger.

Related pages

Related pages on this site...

Bushfires in relation to climate change in Australia

Firewood, an environmentally responsible fuel

Climate change in the international context and in the Australian context

Wind turbines and fires