Habitat: the burning question
Recent large fires in Australia have put the spotlight on land management agencies and their fire management policies and practices. People’s views have tended to polarise fairly quickly into two camps.
In one camp are those who claim the bushfire was an ecological disaster that could, and should, have been avoided had the land management agency conducted more prescribed burning before the fire season.
Others, often from agencies or governments, reassure the public that ‘fire is a natural component of Australian ecosystems’ and that soon they will witness the regeneration of the bush back to its former glory.
According to La Trobe University zoologist Michael Clarke, this polarisation of views is unhelpful and masks how little is known about the needs of fauna and flora when it comes to fire, or the best ways to meet those needs. ‘There are no simple solutions for managing flammable landscapes,’ he says, ‘and we shouldn’t be grasping for them in the heat of the moment.’
The outspoken ecologist is responding to recommendations in a recent Victorian parliamentary inquiry into bushfires and suggestions in the Government’s own Green Paper on Biodiversity to nearly treble the area subjected to prescribed burning each year. ‘This is an unprecedented step in the State’s history. It is a response that appears to be based more on placating public fear of fire rather than scientific evidence of what will work.
‘Fire agencies and volunteers perform an extraordinary service in protecting human life and property in one of the most flammable and fire-prone environments on the planet,’ he says. ‘But alongside this, they are also required to manage fire to achieve effective conservation.’
Dr Clarke is concerned that a trebling of the area burnt each year will not guarantee protection from fires in severe conditions – and may do ecological harm. The responses to fire of plants and animals can differ profoundly from one habitat to the next. Prescribed burning every year may have little impact on biodiversity in tropical savannahs, but be highly detrimental in foothill forests of eastern Australia.
He suggests the government should be extremely wary of extrapolating findings from pine forests in North America or the button-grass plains of Tasmania to, for example, the mallee regions of Victoria.
Dr Clarke is concerned that state-wide prescribed burning ‘targets’ – like trebling the area burnt annually – do not appear to take into account areas that have undergone recent wildfires, creating pressure for overburning in some regions like the Grampians.
The challenge for land managers is to ensure sufficient areas of appropriate habitat are retained to sustain current and future populations of native animals and plants. To do this we need to learn what the animals and plants can tolerate in regards to fire.
Two million dollar study
Dr Clarke has almost completed a two million dollar joint study with Associate Professor Andrew Bennett from Deakin University in the Mallee region of Victoria, NSW and South Australia. The study attempts to shed light on those features of mallee habitats that maximise biodiversity conservation, and how they are affected by fire. It is examining the response of plants, mammals, birds, reptiles, termites, scorpions and scale insects to fires.
‘We know plants have numerous strategies for recovering after fire on a site, such as hard woody protection for seeds, re-sprouting from tough ligno-tubers, thick bark protecting buds, or fire-resilient seeds that survive for decades in the soil seed bank.
‘By contrast, many animals will become temporarily extinct at a site following a fire and rely on re-colonisation of the site, once it recovers, from another source. Provided there are sufficient source populations within dispersing distance, and the key habitat features used by the animal recover at the burnt site, then the animals may well re-colonise. But if the burnt site is isolated or the key habitat features do not recover before the next fire, then the animals may become locally extinct.’
It may not matter much to a re-sprouting mallee tree whether it is in one hectare of burnt habitat or 10,000 hectares. But it matters to a pygmy possum which has to walk to find an unburnt refuge.’
Dr Clarke concludes: ‘If the government decides to increase the annual level of prescribed burning so radically, then it needs a massive increase in its commitment to study the impact of its actions on fauna and flora.
‘Adaptive management – “learning by doing”– requires careful and dispassionate evaluation of the consequences of new policy and, if necessary, the humility to alter course in the light of new information.’