It takes a lot to stop a fire in Australia’s tropical savannas.
Ranked among the world’s most fire prone landscapes and covering some 1.9 million square kilometres, the flammability of Northern Australia is fuelled by a distinctive wet-dry monsoonal climate.
Nonetheless, some features of the same landscape are also known to halt the progress of a blaze.
Exactly where and why this happens has inspired scientists to develop some seriously cool maps of where a hot northern fire front has been stopped in its tracks before, and so might be stopped again.
And the frequency with which fires do stop and fizzle, might surprise you.
Not so lucky are the desert landscapes further south, including the Northern Territory’s iconic Barkly region and Red Centre, which embrace the regional towns of Alice Springs and Tennant Creek, big tourist resorts like Yulara (near Uluru), dozens of remote Aboriginal communities such as Mutijulu, various mines and cattle stations.
Millions of square kilometres of wild desert. The Outback.
Relatively sparse infrastructure and the rivers being generally dry, means the landscapes of dry South don’t really respond to fire in quite the same way as in the North.
And a fire burning a half to a day’s drive from the next settlement quite often goes unheeded.
Thankfully, fire researchers enlisting on-ground help from landowners and managers have a trick or two up their sleeves.
What are fire edge maps?
Northern Institute fire researcher Dr Rohan Fisher has led the research to develop two tools proving a help to fire and emergency managers in Australia’s North, as well as its Centre.
First up is what Fisher calls “fire edge mapping”.
“In the far north,” he explains, “we have an extremely high fire frequency and [almost] 22 years of fire data.
“What we’ve done is add together all the fire edges over those 22 years, so that it basically shows you where fires stop. I’ve then divided that by the fire frequency, so it’s normalised by the number of times a fire has been at that point,” he says.
“What we end up with is a map showing the proportion of fires that have stopped at any one location.”
The number of northern fires in a given year is bolstered by 15 years of prescribed burns in the early dry season, predominantly on Aboriginal land.
The frequency with which fires do stop and fizzle, might surprise you.
Aimed at reducing overall fire extent and severity, the prescribed burns nevertheless add to the overall number of fires evident on satellite images, which yields more data where the scientists can analyse and map fire edges and where they were stopped.
But what exactly is a fire edge?
According to Fisher it is “pretty common sense”: Rivers, roads, fences, cliffs, wetlands; common enough features in the landscape, and ones which will often “pull up fires”.
In Australia’s North, incendiaries are often dropped by helicopter to produce a patch mosaic of early-season burns to create firebreaks.
But it is hard to achieve the desired breaks with any real precision, owing to variable fuel loads on the ground and quite complex terrain, all of which has given rise to a strategy of strengthening pre-existing breaks instead, such as rivers and roads.
Fisher and co-authors Ben Lewis, Owen Price and Anna Pickford, published their investigations into barriers to fire spread in the Journal of Environmental Management in 2022.
As detailed in the paper “the stopping power of each feature type [road, river] was found to vary according to their width and to change during the fire season.”
But how can such fire stoppers in the landscape help fight a fire?
“It’s the sort of thing that local people with good local knowledge, and indigenous knowledge, will already understand of their landscape,” says Fisher.
“But it’s a good way to communicate the information to others, people coming in new to a landscape: It can help them visualise the features that will stop fires.
“And to understand the sort of work you need to do with your own burning to [make best use of] those features, by locating the [existing fire] breaks throughout the landscape.
The researchers assessed the relative fire-stopping power of various landscape features by comparing location, shape and extent, with where historic fires had previously been stopped.
Their efforts have supported a nuanced strategy to understand the landscape.
Upon heading south, however, the scientists encountered a different problem.
Rivers, roads, fences, cliffs, wetlands; common enough features in the landscape, and ones which will often “pull up fires”.
My desert is on fire, but where?
“The fires are much less frequent the further south you go,” says Fisher, “so the data is much less robust as we head into the arid zone.
“There you have many features that are going to pull up fires anyway, and once again, you’re looking at roads, fences, creek lines, maybe ranges; long linear features you can use to help buffer your system.
“[But] in a lot of desert landscapes, it’s more about trying to get diverse “fuel ages” back on to country.
“And when you’re starting from a baseline, and there hasn’t been fire management for quite a while, you have to get in there and slowly build up that age diversity again.”
Fires ravaged the Red Centre’s heritage-nominated Tjoritja West MacDonnell National Park in 2011 and then again in 2018/19 when wildfires burnt 660 square kilometres.
In March, fire destroyed more than 100,000ha of the same park, and last month unseasonal blazes burned more than 25,000ha of the area, threatening nearby Outback capital Alice Springs and blanketing the town in smoke.
By early September as fires closed the Barkly Highway, the whole of the Northern Territory was declared a fire danger zone until at least March next year during which landholders will require a permit to burn.
Many of the fires have been blamed on unchecked and widespread growth in the Centre of buffel grass (or Cenchrus ciliaris), originally sown for soil conservation and considered good feed by some pastoralists.
What help for data-poor southern Australia?
A valuable tool developed for northern Australia is called North Australia and Rangelands Fire Information or NAFI, which is also proving useful in southern desert regions.
Available online or via mobile app, the service helped people in Alice Springs during August fires, when available emergency information was sparse.
Previously, digital fire maps of the NT’s central and southern regions mapped the most recent fire front as ground actively burning within the past six hours.
Now that service has been supercharged.
New data from the Japanese Himawari weather satellite, gives near-live updates of where and how much of an area is currently burning.
“We’ve just added a new hotspot active fire feed to NAFI,” says Fisher, “via a button in the top right that allows you to access a 10-minute interval hotspot.
“The only issue is that while the timeliness of the feed is much higher, the spatial resolution is much lower [at within 3km]”
“You’ll know if the fire is moving, but it doesn’t give you the spatial accuracy to be able to say yes, it’s this close to me now.
“But that’s the best we have at the moment.
“The only other way, which is the way most fire emergency agencies operate, is via on-ground reporting and Bushfires NT.”