Recently I had the pleasure of being part of the annual fire management work undertaken by the Bunuba Rangers and Traditional Landowners on Leopold Downs Station (Yarrangi) in the Kimberley.
It had been many years since any Bunuba people had been up to this remote corner of Western Australia. After driving for hours along a rough 4WD track north of Fitzroy Crossing, getting bogged at almost every sandy creek along the way, we flew by helicopter to Dimond Gorge (Jijirrigi).
A truly spectacular place, Jijirrigi is where the mighty Fitzroy River (Bandaral Ngarri) cuts a swathe through the slabs of ancient sandstone and volcanic rocks of the King Leopold Ranges (Miliwundi), which rise up to more than 900 metres nearby.
The Bunuba rangers knew that the season of Girinybali (February-April) had arrived with the end of the monsoon rains and the first blooming of the bright yellow flowers of gilini (Sesbania canabina) growing in the sand by the rivers.
The dried stems of gilini also make the traditional fire sticks gunggali, which are used at this time of year to create slow moving, patchy fires which only burn small areas at a time and don't spread in to the trees.
This leaves most of the landscape unburnt and allows the country and its plants and animals to regenerate and flourish every year. Girinybali lies in stark contrast to the season called Barrangga or the ‘build up’, which takes place between August and December and begins with the flowering of the bloodwoods each year.
During Barrangga, the landscape becomes gradually hotter and drier with many months of no rain through the dry season until it becomes one of the most fire prone places on the planet. Last year, a fire in the region severely burnt around 70% of the property (more than 310,000ha), and was so hot that it spawned fire tornadoes.
Most tropical woodland and forest areas from Broome to western Cape York have a very high risk of these large bushfires occurring every 2-3 years in August-November depending on rainfall. This is why the fire frequencies of the tropical savannas of Northern Australia are amongst the highest in the world. These large fires continue to combine with the impact of feral animals to cause the small mammal and bird populations to crash in many unmanaged areas and biodiversity to decline across the region.
Thankfully, this year there's enough funding available to plan and implement best practice fire management with the Bunuba Rangers and Traditional Owners in partnership with Bush Heritage. This work will prevent these sorts of large bushfires damaging Bunuba country and surrounding areas.
As with most land management and conservation projects across Northern Australia the aim for the Bunuba rangers is to strategically burn approximately 20% of the landscape in most years. These types of low severity burns avoid damaging fire-sensitive areas or spreading into the foliage of trees and create a patchy mosaic of burnt and long unburnt areas over time that animal and plant populations require for habitat and survival.
This includes species like the Gouldian Finch and Purple Crowned Fairy Wren commonly detected in Bunuba country further to the north. Both these threatened species require riparian areas and adjacent woodlands to be fire free for years to allow all the perennial grass species to seed and provide a critical food source for these species.
Gouldian Finches require the Snappy Gum woodlands with spinifex grasses to be fire free for at least 3 years so there's grass seed available at the end of Barrangga. Gouldian Finch populations have been shown to crash after big fire events which leave no unburnt spinifex grass left in the landscape.
These sort of large bushfires are unfortunately too common across some parts of Northern Australia and also the reason this bird is now a threatened species along with many other animals. This strategic approach to carefully burning small areas across the landscape is the key to maintaining biodiversity, particularly the small mammal and bird populations which are threatened by the prevalent late dry season fires that occur every year across the tropical savannas of Australia.
The job at hand today was to carefully put in some small fires and burnt firebreaks across this vast 405,000ha property to help prevent the spread of bushfires later in the year. We had a small team of four rangers and a senior Traditional Owner for the Jijirrigi area Percy who hadn’t been to that part of his country in many years.
In fact, these remoter areas of Bunuba country had not been managed with fire for many generations and this was the first attempt at landscape-scale conservation work across this vast area for the Bunuba rangers. This required rangers working from vehicles or on foot to burn small areas or use a helicopter to access remoter areas.
However, because of the large, severe fires across Leopold Downs in September/October 2017, the area required to be burnt to protect Leopold Downs from the risk of large fires in Barrangga this year is much smaller – approximately 6% of the property.
These sorts of patchy burns and fire regimes are also ideal for protecting pasture in neighbouring pastoral areas as well as reducing the risk of bushfires threatening remote communities or cultural sites like the thousands of rock art galleries in the region.
The Bunuba Rangers had just finished their job putting in some small fires west of Jijirrigi when a wild scrub bull – which probably hadn’t seen a human in many years – was disturbed from its rest by the noise of our helicopter and angrily chased the rangers and Percy across a rocky plain next to the river and finally in to the safety of some nearby trees. They said it was the first 100 metre sprint Percy had done since he was a kid many years ago but he performed pretty well for an old fella!
The Bunuba rangers have now finished all their fire management work for the season and are hoping that Barrangga is kind to them this year with no big bushfires to threaten the country again.