Fire...friend or foe

An article in The Short Straw series by Lisa Castleman, Agronomist, Ag Services, Riverina Local Land Services (0427 201 963 or lisa.castleman@lls.nsw.gov.au)

I recently completed a short course called Living with Fire, offered through the University of Tasmania. I felt like I needed a fresh perspective, to clarify my own thoughts. The threat of bushfire is in the minds of many Australians with summer approaching as we look to take care of our landscape, our farms, our homes, our families and our livestock.

This season we have received very welcome rainfall and seen the feed grow. This standing carbon is now billowing in the breeze on the side of the road. Grasses, shrubs and trees have all shot away and are prolific in their greenery. Yet as soon as the grasses and cereal crops hay off, this bounty of growth is a potential fire hazard. The soil is our natural resource and protection means looking after our groundcover, which we balance against the needs of grazing animals. The cows and sheep graze the pastures, while the wildlife also graze through the bush and grassy woodlands. The carbon in the pasture grows higher than the fence-lines, while the carbon in the trees grows higher still.

I wanted to share how I feel about fire after the Black Summer of 2019/20. I drove up to Kosciuszko National Park a few weeks ago. I had been aching to see the bush recovering; with the gum trees re-shooting, firstly from the trunk and then with the younger, broad leaves slowly creeping out along the old branches. That was heartening. But there were gullied areas too where the gums stood still, sentinels in the landscape, cold and grey. Some trees won’t come back to life, the fire was too hot in those places, hotter than 300 degrees Celsius, they say.

Life will spring instead from the soil, from the seedbank stored below the charred surface, bursting into life with the elixir of soft rain. The grasses and herbs are re appearing. After months of healing rains, the streams and creeks are all running and tumbling along.

Back to fire, and the first thing I learnt in the course was that fire is not a thing, but it’s a chemical process that happens to things. It’s a process of combustion. Let’s talk ingredients firstly. We need carbon or fuel, we need oxygen, we need an ignition source and heat, hang on. Fires produce heat. Yes, true, they do. But the process of fire requires heat or it can’t start. This can also be explained by saying that the ambient temperature of the air is important, and the higher it is, the more likely that a fire will start or continue to burn for longer. This is ‘because the fuel load is closer to the ignition point at high temperatures’ (Geoscience Australia, 2021).

This reminded me of a camping trip back at Easter, and lighting the campfire was the last task on the list. The new tent had been erected on nightfall, which wasn’t part of the plan to teach the kids about how fun camping was. So there we were, the tent was up and looked good on a (nearly) level site, but the temperature was dropping about 1 degree every 5 minutes because we were just near Mt Selwyn. There was an ample supply of dead firewood close to the site, we had matches to light it with, and my 12 year old had built a great little stook. But we couldn’t get the fire to light. Because we had everything but heat when the ambient temperature was approaching zero, which makes sense now. However, my son persevered and got dead grass to light, which then lit the twigs and so on. It was the coldest night I have ever gone camping on. It literally dropped to below zero that night. One of those teepees made from bear rugs, with a fire in the centre would have done the trick.

As far as the supply of oxygen goes, I learnt that our atmosphere is sitting at 20.9% oxygen at present (Jones, 2021, p. 9). Below 16% oxygen in the atmosphere, a fire simply wouldn’t start, between 16-19% the burn probability is very low and between 19-21% there is a steep increase in the probability of fire (Jones, 2021, p. 9). From a global point of view, the atmosphere is conducive for fire, interesting, although apparently this has been the case for about 55 million years.

So simply put, if we have the ingredients, the carbon (stored in plant materials, the drier the better), oxygen (in the air we breathe) and heat, then we have these seasonal factors which create risk and it is only a waiting game for the ignition source.

Lightning alone is responsible for the majority of fires in the Australian bush. We will never have control over where lighting strikes, although we can manage the risk of welding sparks, vehicle or machinery initiated sparks, and in some cases the risk from burning cigarettes or campfires. As country folk, we all appreciate that placing the campfire where there is no surrounding fuel for sparks to catch, is super important when the grass or bush has a flammable fuel load. Campfires and their embers must always be extinguished properly, which often takes more water than an inexperienced camper might expect or have remembered to keep on hand for the task.

In the Short Course Living with Fire, another lecturer Penelope Jones explained that ‘fire affects some 3-4% of the earth’s surface each year and fire-prone ecosystems cover about 40 % of the land surface today.’ (Jones, 2021, p. 2). Penelope also discussed the ‘incredibly important role of fire in the evolution of land plants and in shaping the distribution of plants, animals and indeed whole ecosystems’ (Jones, 2021, p. 14). Penelope discussed adaptations in the plant world such as thick bark, shedding branches and cones which release their seeds when triggered by fires. The evolution of flowering plants or angiosperms, the dominant plant group, is integrally linked to fire.

The other day I visited a 50 Hectare Woodland that felt very special in terms of native grasses, groundcover plants, a number of Eucalyptus species and birdlife. On that day the reptiles were hiding, although I have seen a lot of Blue Tongue Lizards this spring. During a previous fire event (perhaps in 1952, but maybe later), the local RFS had been successful in ensuring the fire didn’t get into this particular Woodland because it would have burnt for days without fail. This had also coincided with preserving an important part of bush, as the Box-Gum Woodland vegetation type which supports more than 400 plant species is now critically endangered in Eastern Australia.

Fires impact on soil and the increased risk of erosion events, water quality and air quality. The Black Summer fires of 19/20 were estimated to cost the Australian economy $2 billion in their impact on human health alone which included hospitalisations for people impacted by poor air quality.

I think it’s important to understand someone else’s story if they have experienced a fire or a flood. It doesn’t matter whether it happened back in 1931 or 2010, or 2019/20 because it happened during their lifetimes. It won’t have faded away in the memory bank, because it was a significant event for that person. One of our lecturers Acting Professor Fay Johnson elaborated ‘The disruption at the time and then the loss of place, loss of home, loss of livelihoods, loss of significant others, and fear and threats to your very existence - go with the hazards of being at the fire front’ (Johnson, 2021, p. 8). Professor Johnson also explained that ‘preparedness, resilience, sense of community and ability to recover require a focus on community welfare, community support, and individual support at the time of the disaster. Not only can people who have experienced the horror and trauma of a bushfire experience anxiety and depression, but also PTSD. I wanted to use this opportunity to remind us all about preparedness, and the need for ongoing community support.

I write not to trigger your memories of fateful days, but to remind us all that we are vulnerable and it is OK to feel vulnerable. No matter how urbanised the landscape becomes in the cities, we live in the bush. We need to look after ourselves and after the bush.

References:

Johnson, F. (2021). Living with Fire. Health impact of landscape fires, Mod. 1, Ch. 2, pp. 1-22. University of Tasmania.

Jones, P. (2021). Living with Fire. A brief history of fire on earth, Mod. 1, Ch. 3, pp. 1-17. University of Tasmania.

Geoscience Australia (2021). Bushfire. Bushfire | Geoscience Australia (ga.gov.au), Australian Government.