State of the Environment Report 2007
Fire is an important natural feature of the Western Australian landscape. Fires help shape the diversity of plants (Dixon & Barrett, 2003) and animals. Many native plants have evolved fire-related adaptations over time, such as fire-induced flowering or smoke-induced germination (Hopper, 2003). Without human intervention, fires are most often started naturally by lightning strikes. Natural fire regimes (or patterns) have been significantly changed following the arrival of humans. Changed fire regimes have the potential to change ecosystems and the composition of species within. Problems arise when ecosystems are burnt too often. This can lead to loss of biodiversity through inadequate recovery and reproduction times for many plants and animals, resulting in a simplification of ecosystems. Too little fire can also be a problem, limiting reproduction mechanisms for some native plants that use ash, smoke or intense heat to germinate seed.
Aboriginal people traditionally used fire for hunting, cultural and land management purposes. The arrival of Europeans bought a culture of fear of fire, with a focus on fire suppression and preserving human life and property. This is particularly apparent in the South West where prescriptive burns under controlled conditions have been introduced to try and reduce the vegetation fuel load that is available to burn in the event of fires. Fire in the rangelands has historically been used as a pasture management technique, first by the Aboriginal inhabitants and later by the pastoral industry. Fires caused by accidents and arson are also significant.
Understanding the role of fires on biodiversity is complex, and requires an understanding of the frequency (time between burns), seasonality (time of year), intensity (severity) and the extent (area) of the burn. The effect of fire on species and ecosystems varies significantly, further complicating its effect on biodiversity. Often the mosaic pattern in which naturally-occurring fires burnt the landscape has radically changed since European settlement (Dixon & Barrett, 2003).
The extent and frequency of fires are major factors impacting on biodiversity. The Kimberley has the highest frequency of burning (Figure B1.1), with most of the landscape having been burnt over the past 15 years, and some areas burnt annually. Between 80-100% of the Kimberley has been burnt over the same period (Figure B1.2). Widespread areas of the Pilbara, the central deserts, and the South West forests have also been burnt, but much less frequently.
Native vegetation within urban areas is subject to frequent fires as a result of arson, accidental ignition, and invasion by grassy weeds which add to fuel loads. Significant efforts are made in metropolitan areas to reduce the frequency of fire in proximity to people and infrastructure. Frequent fire also poses a significant threat to remnant vegetation in the agricultural zone. Many areas of remnant vegetation are subject to invasion by weeds and fragmentation of ecosystems, and once burnt it is more difficult for recolonisation by native species.
![Figure B1.1: Frequency of landscape burning, 1989–2004. [Data source: Department of Land Information – Firewatch data on frequency of fires outside the South West [ver. 2005]; Department of Conservation and Land Management – bushfire and controlled burning years for the South West [ver. 2005]. Analysis: EPA. Presentation: EPA. Note: The frequency of landscape burning ranges from never burnt to burnt every year. It is possible that some areas are burnt more than once in any one-year period, but this is not distinguished in the methodology.]](/site/files/images/Figure-B1.1_Large.jpg)
![Figure B1.2: Percentage of terrestrial bioregions burnt over a 15-year period, 1989–2004. [Data source: Department of Land Information – Firewatch data on frequency of fires outside the South West [ver. 2005]; Department of Conservation and Land Management – bushfire and controlled burning years for the South West [ver. 2005]. Analysis: Department of Land Information – Firewatch data on frequency of fires outside the South West; EPA - bushfire and controlled burning years for the South West. Presentation: EPA.]](/site/files/images/Figure-B1.2_Large.jpg)
Changed fire regimes have radically changed the environment by threatening fire-sensitive species and altering floristic patterns and vegetation structure, and hence affecting the fauna that depends on that vegetation. Fire-sensitive plants include Gondwana relicts in high rainfall areas. In addition, many species that are not necessarily fire-sensitive can be burnt too frequently and not effectively recover between fires. Fire-sensitive animals are those that have limited capacity to escape, or to find alternative food sources and shelter if fire temporarily removes habitat.
Examples of ecosystems and species at serious threat from too much fire include:
The Kimberley is undergoing irreversible changes to biodiversity due to fires that are too frequent, especially impacts to savanna ecosystems. The savanna region is mainly covered by fire-tolerant species, but is interspersed with some fire-sensitive species. These tend to be plants which must set seed instead of being able to reproduce vegetatively, have a maturation period of at least three years, are usually restricted to rugged sandstone habitats, and form tropical forests and woodlands (Yates & Russell-Smith, 2003). These areas need to be managed to preserve patchiness or mosaic at a landscape level
The Arnhem cyprus pine (Callitris intratropica) has a distribution in savanna areas of the Kimberley region, and has been suggested as a useful bio-indicator of changes to fire regimes. This tree species is long-lived, obvious in the landscape, covers a wide range of environments, and remains visible for many years after it has died (Bowman & Panton, 1993; Graham, 2001). The Arnhem cyprus pine is very fire-sensitive at seedling and sapling stage and requires at least 12 years to mature. It has limited seed dispersal from the parent tree, and has short-term seed viability (Graham, 2001). Adult trees are killed by high intensity and frequent fires, but are undamaged by low intensity fires. Surveys between 1998 and 2000 showed that approximately 50% of all Arnhem cyprus pines examined were dead, very few showed signs of re-sprouting, and there were limited numbers of saplings (Graham, 2001). In some areas, up to 100% of the trees were dead, indicating that high intensity and frequent fires are severely impacting this species.
Frequent large, hot, late-season fires can destroy the important mosaic of growth, maturity and species composition across the landscape (T Start, Department of Conservation and Land Management, pers. comm.). One consequence of changes to extent, seasonality and patchiness of fires in the Kimberley is a change of grass species composition from perennials to annuals (Graham & McKenzie, 2004). Frequent wide scale fires apply selection pressure on the landscape, so annual grasses that grow quickly and then die off are at an evolutionary advantage. However, once this trend begins, large areas of dead grass at the end of the dry season provide ample fuel for naturally-occurring or human-induced fires to start and travel long distances. The reduction in abundance of perennial grasses has also had a large impact on trees or woodland plants, and many grain-eating animals such as finches (Graham & McKenzie, 2004).
Fire prompts flowering of some native plant species, and many use ash, heat or smoke as a germination medium for seeds (sometimes known as 'fire-opportunists'). The burning of existing vegetation also allows regeneration from seeds stored in soil. Some plants thought to be extinct or rare have had significant range extensions after a fire, including the many stemmed lily (Sowerbaea multicaulis), the showy eremophila (Eremophila racemosa), Calamphoreus inflatus and E. veneta (Yates et al., 2003). Spinifex species are very flammable and are adapted to the patch burning regime used by Aboriginal people. In predominantly urban and agricultural landscapes and some conservation estate and unallocated crown land areas, fires have often become either large-scale burns or have ceased. Animals that have a competitive advantage after a fire are those that can move relatively quickly away from the fire front, and then recolonise an area to take advantage of new shoots, as the vegetation begins to return, or increased availability of prey.
Lightning strikes are a common natural ignition source of fires. The North Kimberley has the highest number of lightning strikes in Western Australia (and also Australia), with an average of between 8 and 12 lightning strikes per square kilometre hitting the ground annually (Kuleshov et al., 2006) (Figure B1.3). Electrical storms, common in the Pilbara and Kimberley, can result in the ignition of multiple fires across a vast area at the same time. These fires are particularly difficult to control due to the vast areas of land and their inaccessibility.
![Figure B1.3: Average annual lightning ground flash density. [Data source: Kuleshov et al. (2006). Note: Analysis generated from NASA Optical Transient Detector and Lightning Imaging Sensor data (0.5 degrees grid resolution) averaged over the 8-year period 1995-2002. The satellite data were calibrated against the ground-based Lightning Flash Counter data and adjusted accordingly.]](/site/files/images/Figure-B1.3_Large.jpg)
Land holders (such as pastoralists, Aboriginal people and conservation managers in the rangelands) use fire for different reasons. In 2005, 27% of pastoralists undertook a prescribed burn for management purposes (Department of Agriculture, 2005). Fire is often used as a management tool for vast and inaccessible landscapes and can act as a selection pressure for species found in an area. Fire is useful for promoting new growth in plants that is palatable for livestock, but the frequency of burning (especially in the Pilbara and Kimberley regions) is too high for the long term survival of many native species. Aboriginal people also continue to use fire for traditional hunting, cultural or land management reasons. The way in which Aboriginal people burn the landscape has changed over time, with much less of their traditional land being burnt since 1920 than occurred before that time. This is a result of past social policies (the removal of Aboriginal people from the land), and more Aboriginal people having moved into towns (spending less time in their country).
Prescribed burning practices in the South West forest region have caused conflict within government, the general public, and scientific communities. Some advocate use of controlled burns to reduce fuel loads and bushfire intensity, and to protect human life and property. Others contend that prescribed burning does not have a preventative effect for bushfires and has many negative consequences for biodiversity (such as eliminating fire-sensitive species and facilitating the spread of weeds). Prescribed burns are carried out by State Government agencies for land management purposes. Agencies have faced criticism because prescribed burns are a risk to biodiversity as they do not adequately mimic pre-European settlement burning regimes. This is comprehensively addressed in two recent EPA reviews (Environmental Protection Authority, 2004 & 2006). The area actually burnt is dependent on climatic and weather conditions and available agency resources (Environmental Protection Authority, 2004).
Fire management: The Department of Environment and Conservation conducts a program of controlled burns on land which it manages in order to protect and conserve biodiversity values, human lives and community assets. Controlled burning is undertaken to reduce the occurrence and impacts of large, intense wildfires, and regenerate and protect forest ecosystems following harvesting operations or other disturbances.
Fire fighting: The Fire and Emergency Services Authority, volunteer bushfire brigades and the Department of Environment and Conservation are responsible for responding to fires and attempting to control or extinguish them. Local councils and individual landholders are responsible for maintaining firebreaks.
Environmental Protection Authority fire reviews: In 2004 the EPA undertook a review of the former Department of Conservation and Land Management's controlled burn practices in the South West forest region. A review of fire management in the Kimberley and other rangeland regions was also released for public comment in 2006.
Research: The Department of Environment and Conservation is undertaking research on the effect of fire regimes on species richness and composition in the southern jarrah forest; fire behaviour in dry eucalypt forest; the effect of fire on cave systems, fungi and short range endemic species; the interactions of landscape and fire management; the effects of fire on invertebrate biodiversity. It is also undertaking post-fire monitoring in Nuyts wilderness area (near Walpole). Some research projects are done in collaboration with the Bushfire Cooperative Research Centre. Project Vesta is a collaboration between CSIRO and the Department of Environment and Conservation to research fire behaviour and management, specifically in dry eucalypt forests. The project is designed to establish the effect of fuel load and structure on fire behaviour and provide insight into long-term effects of prescribed burning on bushfire behaviour.
Cooperative research centres: State agencies, the Department of Environment and Conservation, the Fire and Emergency Services Authority and the University of Western Australia form part of the Bushfire Cooperative Research Centre. This centre provides research to aid management of bushfire risks to the community in an economically and ecologically sustainable way. The Cooperative Research Centre for Tropical Savannas Management includes the CSIRO, Department of Agriculture and the Department of Environment and Conservation, and conducts research on fire management and the effects of fires on vegetation and weed spread.
Firewatch: This program is run by the Department of Land Information through the Leeuwin Centre at CSIRO. It collates satellite imagery to produce accurate and up-to-date information to emergency services, land managers and land holders. It can also be used to compile long-term information such as seasonal and annual data, fire frequency and locations or areas burnt.
The implications of inappropriate fire regimes are very serious for the environment, society and the economy. Fires that occur too frequently across large areas or at an inappropriate time of year cause loss of habitat and food supply for native species, loss of landscape diversity and degradation problems for land and inland waters. Fires can also exacerbate or cause additional threatening processes to occur such as soil erosion, release of particulates to the atmosphere, weed invasion, eutrophication, salinisation, and also increase the spread of Phytophthora dieback through fire fighting operations. Fires can also result in the release of greenhouse gases and reduce carbon sequestration by plants. Very intense fires which kill mature native vegetation can contribute to long-term ecological change by removing adults and leaving new seedlings vulnerable to climate stressors such as drought. Further loss of species and the simplification of ecosystems are likely if inappropriate fire regimes persist. Changed fire regimes are an emotive issue and causes frequent debate amongst local communities. In urban areas, there is significant effort to reduce the frequency of fires so as to prevent loss of life and damage to housing and associated infrastructure. In agricultural and pastoral areas, fires can cause significant productivity loss and damage to crops, plantations, feedstock, water supplies, farm infrastructure and livestock. The decisions made to protect humans and infrastructure that are made on economic and social grounds have important effects on biodiversity.
5.5 Establish a comprehensive condition monitoring program to determine trends in biodiversity as a result of changed fire regimes.
5.6 Implement the EPA's Review of the Fire Policies and Management Practices of the Department of Conservation and Land Management (now Department of Environment and Conservation).
5.7 Implement the recommendations of the EPA's Fire Management of the Kimberley and Other Rangeland Regions of Western Australia.
