A. Malcolm Gill

Fire and The Australian Flora: A Review

SUMMARY Fire is a natural environmental variable over most of Australia. It is a unique environmental variable in that it: tends to be self propagating; occurs for extremely limited periods in any one locality; may have devastating effects; occurs over a wide range of environments and plant communities. In many ecosystems fire is a normal environmental variable. Its immediate effects on vegetation depend on fire intensity but longer-term effects depend also on fire frequency and season of occurrence. Using these three variables, various fire regimes may be defined. Species may be adapted to these fire regimes but not to fire per se. Interaction between fire and an adaptive trait may facilitate survival or reproduction of a species but this effect alone does not guarantee that the species is adapted to a certain fire regime—this depends on many characteristics of the life cycle. Much of the relevant Australian literature is concerned with adaptive traits while relatively little considers adaptations of spe...

Learning to coexist with wildfire

The impacts of escalating wildfire in many regions — the lives and homes lost, the expense of suppression and the damage to ecosystem services — necessitate a more sustainable coexistence with wildfire. Climate change and continued development on fire-prone landscapes will only compound current problems. Emerging strategies for managing ecosystems and mitigating risks to human communities provide some hope, although greater recognition of their inherent variation and links is crucial. Without a more integrated framework, fire will never operate as a natural ecosystem process, and the impact on society will continue to grow. A more coordinated approach to risk management and land-use planning in these coupled systems is needed.

Bushfires 'down under': patterns and implications of contemporary Australian landscape burning

Australia is among the most fire-prone of continents. While national fire management policy is focused on irregular and comparatively smaller fires in densely settled southern Australia, this comprehensive assessment of continental-scale fire patterning (1997-2005) derived from ∼ 1k m 2 AdvancedVery High Resolution Radiometer (AVHRR) imagery shows that fire activity occurs predominantly in the savanna landscapes of monsoonal northern Australia. Sta- tistical models that relate the distribution of large fires to a variety of biophysical variables show that, at the continental scale, rainfall seasonality substantially explains fire patterning. Modelling results, together with data concerning seasonal lightning incidence, implicate the importance of anthropogenic ignition sources, especially in the northern wet-dry tropics and arid Australia, for a substantial component of recurrent fire extent. Contemporary patterns differ markedly from those under Aboriginal occupancy, are causing significant impacts on biodiversity, and, under current patterns of human popula- tion distribution, land use, national policy and climate change scenarios, are likely to prevail, if not intensify, for decades to come. Implications of greenhouse gas emissions from savanna burning, especially seasonal emissions of CO2, are poorly understood and contribute to important underestimation of the significance of savanna emissions both in Australian and probably in international greenhouse gas inventories. A significant challenge for Australia is to address annual fire extent in fire-prone Australian savannas.

Intervals between prescribed fires in Australia: what intrinsic variation should apply?

Abstract Because of increasing concern over the constancy of intervals between prescribed fires within a vegetation type, we examine various sources of evidence that can be used to determine variation appropriate to the conservation of biodiversity while minimizing the chances of economically destructive fires. Primary juvenile periods of plants (especially of ‘serotinous seeders’) and non-breeding periods of birds (especially poorly dispersed species) suggest extreme lower limits for fire intervals whereas longevity of plant species which usually only reproduce after fire, set the extreme upper limits. Modelling of the behaviour of selected plant and animal species may be used to set ‘optimal’ mean intervals. Historical fire-interval data might seem a useful way to determine the variation about the mean fire-interval but data are scarce and interpretations are controversial. The Weibull distribution and its special case, the negative exponential distribution, have been the most supported in North American studies of unplanned fires. It has been argued that fire-interval distributions, before European settlement at least, were largely the result of large fires during, or following, extreme weather events (dry in forests, wet in the arid zone). Long weather records are most beneficial when they can be related to the areas burned each year. Practical solutions to the question ‘what range of fire intervals should be used at any one site’ may be achieved using highly simplified skewed distributions, constructed on the basis of land-management objectives.

Fire regimes in mountain ash forest: evidence from forest age structure, extinction models and wildlife habitat

The mean interval between tree-killing fires in mountain ash (Eucalyptus regnans F. Muell.) forest was inferred from information on the age structure of unlogged forest, the prevalence of mountain ash trees in the landscape, and on the abundance of live and dead hollow-bearing trees. The analyses were based on models of the local extinction and recolonization of forest patches by mountain ash trees and of the development of hollow-bearing trees in response to time since fire. The results of the analyses suggested that the mean interval between tree-killing fires was between75 and 150 years in mountain ash forest. Data on mortality of mountain ash trees suggest that approximately half the trees survive fire, making the mean interval between all fires equal to 37‐75 years. The model predicts that the proportion of the landscape occupied by mountain ash will decline sharply as the mean fire interval decreases, suggesting that changes in the fire regime may have abrupt and major effects on ecosystem properties. # 1999 Elsevier Science B.V. All rights reserved.

Large fires, fire effects and the fire-regime concept

‘Large’ fires may be declared so because of their absolute or relative area. Huge fires – with areas of more than 106 ha (104 km2) have occurred across a wide spectrum of Australian environments and are known on other continents. Such large fires are rare whereas fires with much smaller areas are common. Large fires are initiated by single or multiple ignitions and become large because of some combination of: rapid rates of spread; long ‘life’; merging, and failure of initial suppression operations. Fires as ecological ‘events’ occur within a ‘regime’ – an historical series. Both events and regimes have effects that may be discerned in terms of water, land, air or organisms. What have been regarded as the components of ‘regimes’ have differed between observers, the main issue being whether or not spatial variables need to be included; ‘area’ involvement is briefly addressed. The current trend toward fire-regime control through fuel treatment, including management (prescribed) burning, and fire suppression may be expected to continue. These trends, among others, can be expected to change fire regimes. What is regarded as ‘large’ among fires may change as the planet becomes increasingly human-dominated.

Fire regimes and biodiversity: the effects of fragmentation of southeastern Australian eucalypt forests by urbanisation, agriculture and pine plantations

Abstract Fragmentation of eucalypt forests has been common in southeastern Australia. Urbanisation, agriculture and the establishment of plantations of the exotic tree Pinus radiata are major agencies of fragmentation. The study of the effects of these agencies on adjacent forested land has lacked a suitable framework. By constructing generalized trophic-level diagrams for each fragmenting system—farm, urban area and pine plantation—the major potential impacts on adjacent forested land can be examined. Urban areas, for example, have a relatively large non-native predator biomass (especially cats and dogs) compared with the original forest, whilst farms support a relatively large biomass of exotic herbivores. In pine plantations, by way of contrast, the biomass of native or exotic herbivores and predators is relatively small. Landscape fires are an integral part of the ecology of native eucalypt forests but are kept out of suburban areas, farms with improved pastures and standing plantations as much as possible. To explore the potential impacts on biodiversity of fire regimes in forests at the edges of urban areas, farms and plantations, we constructed and sought evidence for, a series of scenarios (each a compound hypothesis). Urban interface scenario : ‘There is a low frequency of unplanned fire in forest remnants. To prevent losses of life and property in adjacent urban areas, regular frequent prescribed burning is practiced. Regular frequent prescribed burning reduces biodiversity’. Support for the first two parts of this scenario was strong although the frequency of fires, prescribed or unplanned, may be a function of distance from the urban edge, the size of management unit and the nature of the tuels. Urban predators may be expected to reduce vertebrate biodiversity, especially after fires. Agricultural interface scenario : ‘Clearing for agriculture leaves only small forest remnants with become fire free. Fire-free fragments eventually decline in plant species biodiversity’. Forest fragments in rural areas vary widely in size and occur as roadside remnants, farm woodlots, Travelling Stock Reserves, State Forests and designated conservation reserves. The circumstances of burning vary widely. Grazing from domestic stock, especially combined with fire, may negatively affect biodiversity. Absence of fire may also reduce biodiversity. Pine interface scenario : ‘Pines spread from plantations to neighbouring forest areas, reducing native plant and animal species diversity. This situation can be reversed by a prescribed burning regime that has fires intense enough to cause pine death and frequent enough to prevent pine seed set’. There was considerable support for this scenario although at this stage the spread of pines may be only in areas peripheral to plantations. Because fires have effects on biodiversity, crops, lives and property in fragmented forests and adjacent areas, integrated management—across landuses and jurisdictions—is recommended.

Theoretical fire-interval distributions

Models for fire interval distributions in ecological communities are proposed, based on an understanding of the processes that influence the probability of fire, especially changes to the amount and condition of the fuel. The models represent changes in the probability of fire as a function of time since last fire. Despite considerable differences in the probability distributions of fire intervals, the models generate very similar age distributions when the mean fire interval is the same. Therefore, fitting the theoretical distributions to observed landscape age structure is unlikely to allow discrimination between different models. Previously, the most commonly used models of fire intervals have been based on the Weibull probability distribution. We believe that this is unnecessarily restrictive, and a broader range of models should be considered. The models may be based on an a priori understanding of the ecosystem being studied. They should assist interpretation of observed or inferred fire interval distributions.

Interactive simulation of bushfires in heterogeneous fuels

The program IGNITE, developed by the authors, is a landscape fire modelling system that deals with fires in heterogeneous fuels. Landscapes are represented as cellular automata (grids of pixels) and fire spread is modelled as an epidemic process. An integrated geographic information system permits the importing and editing of maps from compatible sources, such as satellite imagery. Maps, models and other information are organized as scenarios; historical fires can be recorded and replayed. Modules are being developed for application to fire prevention, fire suppression, land-use management, and to training and education. An illustration of using the system to deal with heterogeneous fuel is its application to the problem of percolation in patchy fuel.

A review of current space-based fire monitoring in Australia and the GOFC/GOLD program for international coordination

Satellite remote sensing of fires provides a unique view of our planet and quantitative information that can inform resource management and policy. Operational and experimental satellite sensing systems have the capability to provide regional and global monitoring of fires. These systems provide different types of fire information for estimation of fire danger, detecting active fires, estimating burned area, quantifying emissions products, estimating fire damage and monitoring post-fire ecosystem recovery. Efforts to extract and provide such information fall largely in the research domain and are in various stages of development. The pressing demand for reliable and up-to-date information, on fire occurrence, extent and emissions, warrants the transition of the mature research methods and experimental sensors into the operational domain. Providing consistent, timely and easily useable fire information of known accuracy for improved resource management is a challenge facing the research and operational communities. As part of the Integrated Global Observing Systems initiative, an international program called Global Observations of Forest Cover/Global Observations of Land Dynamics (GOFC/GOLD) is coordinating a concerted effort to meet this challenge. This paper describes the goals of this international program and provides a case study of the development and current status of satellite-based fire monitoring in Australia. We identify the major obstacles to a broader adoption of the technology by the fire community, the current needs and the relevance of the broader international program to national satellite-based fire monitoring activities.