Living in a land of fire
Professor Rob Whelan, University of Wollongong
Professor Peter Kanowski, Australian National University
Dr Malcolm Gill, Australian National University
Dr Alan Andersen, CSIRO Tropical Ecosystems Research Centre
prepared for the 2006 Australian State of the Environment Committee, 2006
Bushfires hit the headlines in southern summers, emphasising death and destruction. The media often report ‘destruction’ of the bush as well. The bush is not destroyed; fires have occurred before, over many millennia, and the bush has recovered. Plants regenerate and animals survive, even when no one could imagine that this could be the case, such as when fires burn through the crowns of woody plants and a completely blackened scene is created. Recolonisation starts occurring after the bush has been burned (not ‘destroyed’). Burning can certainly cause changes to the bush—population sizes of plant and animal species will change and it is possible that some species may be lost from a burned area, temporarily or even permanently.
Bushfires focus our attention on individual people and individual structures as priceless assets, and as a society we face a complex challenge of finding ways to protect these human assets. The lower the intensity of a fire, the easier it will be to protect adjacent property. Fuel is the one factor determining fire intensity that humans can manipulate readily. If fuel is limited, then fires cannot reach the same potential that they could if fuel was allowed to accumulate without restriction. This principle underlies fuel-reduction burning as an approach to bushfire mitigation. Fires that are prescribed to achieve fuel-reduction need to be repeated frequently enough to keep the fuel below certain critical levels.
The persistence of plants and animals is influenced by their inherent characteristics and by fire intensity, interval between fires, seasonality, and type of fire over a period of time—this is referred to as the fire regime. Not all species respond the same way, so there is a variety of responses to each individual fire as well as to the fire regime. Species may be favoured by one fire regime but be threatened by another. Thus, ‘inappropriate fire regimes’ are quite often listed as threatening processes in legislation. An inappropriate fire regime for some species may be frequent fires, whereas lack of fire, or high intensity fires, or low intensity fires may be inappropriate for others.
Biodiversity is a convenient term that is used to describe aggregates of species, which, in turn, are aggregates of populations and individuals. Conservation of biodiversity is about avoiding the extinction of local native species. A common misconception is that all Australian species are unaffected by fires. Research clearly shows that the flora and fauna may be adapted to certain fire regimes but not to others.
In many environments where human assets abut bushland in which conservation of biodiversity is a key management objective, achieving a fire regime that facilitates protection of property will compromise conservation of some species. This situation is at the core of many heated arguments about bushfire mitigation strategies—protection of properties versus conservation of biodiversity.
This is a very complex issue that is often treated simplistically; a simple response for property protection (reduce fuel over the whole landscape) will compromise biodiversity conservation, and a simple conservation response (avoid fire regimes that are inappropriate for the local biodiversity) will compromise property protection. Even recent suggestions that using fuel-reduction burning to create ‘mosaics’ of different fire ages will provide fire protection for houses without damage to the environment are simplistic. Mosaics come in many forms and create their own arrays of fuel patterns and fire regimes that will have as yet untested effects on the potential for protection of property and biodiversity change.
Effective responses to this ‘land use conflict’ will require a more sophisticated understanding of the locations of biodiversity assets in the landscape, the responses of organisms to particular fire regimes, and bushfire behaviour in particular situations of fuel load, fuel distribution, topography and climate.