Ecologist Murray Haseler, Ecological Monitoring Coordinator Dr Jim Radford and Carnarvon Station Reserve’s former Reserve Manager Darren Larcombe explain why actively managing fire is fundamental to managing most Australian ecosystems.
Burning in cool, still conditions soon after rain means lower mortality of shrubs and regenerating trees and fauna, and a patchy coverage that gives shelter or respite to a greater range of species. Photo Darren Larcombe.
Rarely have we experienced such a contrast of climatic conditions across the country as we have in recent times. Record rainfall has brought floods and lush growth across northern Australia yet the ‘big dry’ continues unabated in the south.
For Bush Heritage, with reserves spread across the continent, such variation presents great challenges for managing fire on our reserves.
Australian ecosystems have evolved under the influence of fire to some degree, and it's neither desirable nor possible to totally exclude fire from Australian landscapes. As land managers we have a responsibility to actively manage fire on all our reserves to achieve three generic goals:
- to protect human life and property infrastructure and assets;
- to reduce the risk of large, unplanned wildfires; and
- to enhance conservation and cultural values.
Patchy cover after a controlled burn. Photo Darren Larcombe.
Exactly how we manage fire to achieve these goals, however, will vary considerably from reserve to reserve, depending on previous fire history, soils, vegetation types (and associated drying rates and flammability) as well as climate, seasonal conditions and terrain.
Fire can be managed or fought – extinguishing unplanned and unwanted fire when it occurs, or conversely, deliberately lighting fires (planned burning) to achieve particular conservation outcomes (e.g. weed control, regeneration of native ecosystems) or to reduce the risk of unplanned fire.
Striking a balance requires sound knowledge of the ecological values we're seeking to enhance on a given reserve as well as how those values respond to different fire regimes. An overview of fire management at Carnarvon Station Reserve is presented here to illustrate the complexities of managing fire on a large reserve.
Case study: Carnarvon Station Reserve
Carnarvon Station Reserve spans 56,000 ha and is situated 600 km west of Bundaberg in Queensland.
The reserve extends over a valley with a grassland floor (bluegrass downs) flanked by often rugged slopes with a variety of woodlands, acacia shrublands, vine-scrubs and open forests.
Woodlands in the east of Carnarvon Station Reserve, six weeks post-burn. Photo Jim Radford.
All the grasslands and woodlands are flammable and many species are fire-dependent (or dependent on the structure resulting from particular regimes). The acacia shrublands (brigalow and lancewood) and vinescrub are less flammable but will burn in extreme conditions, are fire sensitive and are nationally threatened communities.
Until purchase in 2001, Carnarvon’s long past as a cattle station shaped the kind of fires the property has experienced. One hundred and fifty years of livestock grazing had reduced fuel (grass) loads, limiting fires to late-season hot wildfires following summer rains.
Typically, these unplanned and uncontrollable fires – the type that pose considerable threat to people, natural resources and infrastructure – would burn extensive areas of the property.
Bush Heritage has adopted a proactive approach to avoid these large-scale destructive fires. The generic approach is to maximise the diversity of fire regimes in an area – ‘breaking the country up’ to create a mosaic of different fire ages and fire histories – to maximise the reserve’s contribution to overall biodiversity conservation and reduce the risk of extensive wildfires.
This means lighting literally hundreds of fires in moist conditions to get a dozen or so successful and safe burns. Reserve managers work with natural fire boundaries, such as creeks, escarpments, recently burnt areas and non-flammable vegetation, to contain fires.
By placing cool burns among natural boundaries, it's possible to create large, non-destructive fire breaks that are much more effective than a bulldozed line.
Lighting up with drip-torches rather than matches enables ignition in the moist and/or low-temperature conditions ideal for ‘cool’ burning. Photo Darren Larcombe.
This kind of planned burning requires skills in judgement and practical application, as well as an intimate knowledge of the terrain, vegetation and local weather behaviour. It's not an exact science, especially following sequential wet years, and occasional hot fires will still be inevitable. However, given resources, expertise and support, it can be assured that the net negative impact of such wildfires will be less.
This year, all Bush Heritage’s Queensland reserves experienced soaking conditions for the second year in a row, but even as they celebrate the abundance of life the rains have brought, none of the reserve managers need reminders that today’s flood is tomorrow’s inferno.
As the vegetation and soils dry out, there's a potentially narrow window of opportunity during the cooler months to light fires that will put themselves out as they hit changes in terrain, cool overnight temperatures or fire breaks.
These cool-season fires will leave old growth trees intact and leave patches of bush unburnt (thereby providing habitat for surviving animals).
We can and do tweak this approach to assist with particular species or ecosystem requirements. For example:
- hot burns during springtime to facilitate germination of natural grasslands;
- cool burns around weed-infested areas to allow contained hot fires to kill weeds;
- cool burns in the woodlands that leave the shrubs to provide bird habitat, interspersed with some hot burns to provide future tree hollows for animals or to provide effective strategically located wildfire breaks.
Carnarvon’s native grasslands are recovering well following the removal of stock, with a few species of grass providing a ‘wick’ right up the core of the property. These areas have been burnt frequently, with approximately a third of the total area burnt each year.
This doesn't mean, however, that all areas are burnt every three years: the fires overlap, snaking around some bits not burnt the year before and burning some areas in successive years. The result is a fine-scale grassland mosaic with fire ages ranging from a month to one, two or five years or more, and patches that experienced cool and hot, and summer or winter burns.
Fire management doesn't end once the burns have been extinguished. Each year the burn areas are mapped from satellite images and the maps checked for accuracy on the ground.
A retrospective look at the fire mapping illustrates the transformation from an unmanaged landscape to one with managed fire regimes. Our ecologists are monitoring small mammal populations, birds and the mix of native and introduced grasses to evaluate the ecological outcomes of our fire management.
Owning and protecting the bush is one thing, but a nature reserve is only as good as it is resilient. For a long-term conservation plan, the ultimate measure of a reserve’s resilience is how well it recovers from the worst-case scenario, in this case a hot, extensive wildfire in what is likely to be a very bad fire season.
Right now, thanks to a successful burning season, the worst-case scenario for Carnarvon Station Reserve doesn’t look that bad. Moderating the impacts of fire on bushland with careful fire management is our investment in building the resilience of our properties in a changing world.