SoE 2003 > Biodiversity > 6.5 Fire

6.5 Fire

Knowledge on appropriate fire management regimes is improving slowly, but a sustainable regime for managing NSW landscapes is still needed

Fire is a key natural factor in Australian ecosystems. Trying to suppress or even exclude fire can set the scene for later wildfires of high intensity that can have a severe impact on biodiversity (and the built environment). Current hazard reduction burning practices differ from the regime practised by Aboriginal people prior to European settlement, and they have caused the composition of ecosystems to change. A management balance that preserves ecosystem structure, safeguards threatened populations, and ensures the safety of the community and the protection of assets has yet to be achieved.

NSW Indicator

Importance of the issue

Fire is an important part of the Australian landscape. Much of the country's flora and fauna has evolved in the presence of fire, and inappropriate fire regimes may significantly reduce biodiversity within a region. To maintain biodiversity, fire regimes must be managed carefully as various species respond differently to changing regimes. Major fires since State of the Environment 2000 (EPA 2000b) have caused substantial property damage and affected large areas.

Understanding the effects of fire on ecosystems requires a knowledge of the frequency, seasonality, intensity and extent to which different types of vegetation are burned. In addition, the effect of fire varies between species and ecosystems, complicating interpretation of its effects on biodiversity. The impacts of high-intensity wildfires and low-intensity fuel management burns occurring at similar intervals or regular lower intensity fires are also quite different.

Information about the extent and season of bushfires and prescribed fires is largely confined to those areas managed by State Forests of NSW and the NSW National Parks and Wildlife Service (NPWS). The intensity of wildfires is often not recorded, but it is usually included in the post-burn assessments of hazard reduction and prescribed burning.

Recent studies have suggested that fires in the past, including those lit by Aborigines, were largely confined to the fire season of spring and early summer (McLoughlin 1998). By contrast, 60% of prescribed burning for asset protection in northern Sydney between 1980 and 1995 was conducted in autumn and winter. While the changes to fire patterns are known at a basic level, the effect of these imposed regimes on biota has not been studied comprehensively across NSW.

Historically, fire patterns have been a fine mosaic of numerous small interlocking burnt patches with the occasional large fire scar. This pattern is believed to have been practised by Aboriginal communities for tens of thousands of years, and biological communities adapted to this regime. Fire patterns after European settlement have generally changed to a simpler, coarser pattern of large fire scars and large tracts of long-unburnt vegetation. This pattern is widely considered to cause much larger fires and fire scars on the landscape (Williams et al. 2001).

Changing fire regimes have been associated with the decline of many biological communities. For example, local extinctions have been recorded for some plants, species in natural woodlands are declining, and the loss of fire-sensitive wet-forest trees means areas of wet-sclerophyll forest and rainforest are becoming dominated by dry-forest species. Other plants are facing complete extinction from alterations to fire regimes. Small mammals have been affected, as well as up to 40% of all mainland bird species (Williams et al. 2001).

Fires may also have significant consequences for water quality and aquatic ecosystems. The scale of impact of fire on water quality and aquatic habitat depends on a number of factors, including its intensity, the timing and intensity of post-fire rainfall, topography, geology, soil type and vegetation patterns. High-intensity wildfires can have more serious environmental consequences as they are able to consume all of the surface vegetation and leaf litter, which in turn generates a nutrient-rich ash and directly exposes the soil surface to rainfall. This may increase the risk of soil erosion. The fire may also modify soil surface properties by making it more water-repellent. This, combined with reduced water uptake by plants, increases the amount of water runoff, which transports the sediment and nutrients from burnt areas to receiving waters, degrading water quality and aquatic habitat.

In 2001, bushfires consumed 7500 square kilometres (km²) of NSW bushland and threatened the quality of Sydney's water supply. Over 1200 km² of bushland was burnt across the city's water supply catchments. In the worst affected areas, Lake Woronora and Lake Avon, almost the entire catchment was burnt. The fires were very intense and removed most of the surface vegetation. Heavy rainfall, shortly after the fires, caused extensive localised erosion and sedimentation, opened up gullies, and increased turbidity levels in receiving waterways. Although the water supplied to consumers was unaffected, fish kills occurred in parts of the catchment because of sediment from burnt areas.

NSW's 2002–03 fire season was the most protracted and demanding in decades with some local bushfire danger periods declared as early as July 2002. Nine months of firefighting followed, including 151 days of consecutive bushfire emergency declarations which finally ended in February 2003. The fires primarily affected inaccessible terrain in the Northern Tablelands, North-west Slopes, Mid-north Coast, Hunter, Southern Tablelands and South Coast areas. In total, fires consumed almost 1.5 million hectares and included extensive property damage from Queensland to the Victorian border (RFS data, as at June 2003).

Table 6.7 compares details of the worst recent bushfire seasons.

Table 6.7: Comparison of recent serious bushfire seasons

Source: RFS data, as at June 2003

Response to the issue

A major effort has been made to reach a balance between the need to protect property through prescribed or hazard reduction burning and to optimise the conservation of biodiversity by managing fire regimes. The key responses being used to manage the impacts of fire on biodiversity are:

• guidance on appropriate fire regimes and hazard reduction burning
• fire management plans for fire-prone reserves and bushfire districts
• data collection activities.

The National Strategy for the Conservation of Australia's Biological Diversity (DEST 1996) and the NSW Biodiversity Strategy (NPWS 1999a) both recognise the importance of managing fire in conserving biodiversity. Guidelines have been developed for identifying appropriate fire regimes which conserve biodiversity within given ecosystems.

The Rural Fire Service (RFS) has developed the Bush Fire Environmental Assessment Code (RFS 2003). The code provides for an integrated environmental assessment of hazard reduction works and the issue of a certificate setting conditions to mitigate any associated adverse environmental impacts. All matters affecting or likely to affect the environment, such as critical habitat, threatened species populations and ecological communities, are considered. The RFS and local councils issue certificates to private landholders. Government agencies with land management responsibilities may also use certificates to certify bushfire hazard reduction work. If a certificate cannot be issued on environmental grounds, the proposal is then subject to the existing legislative regime rather the code's integrated assessment approach.

Planning for fire management is required by the Rural Fires Act 1997 and the Native Vegetation Conservation Act 1997. Under the Threatened Species Conservation Act 1995, 'high frequency fire' is listed as a key threatening process, requiring preparation of a threat abatement plan.

NPWS is developing Reserve Fire Management Plans incorporating specific biodiversity conservation objectives based on the fire response characteristics of broad vegetation groupings. A zoning system allows for different priorities to be assigned within reserves, balancing biodiversity conservation with the protection of life, property and places, such as heritage sites. Plans are being developed for over 200 fire-prone reserves. Over 30 have been finalised and more than 150 are in draft form or nearing completion (Williams et al. 2001).

The RFS is coordinating the development of Bushfire Risk Management Plans for all bushfire districts in NSW. These aim to coordinate planning to protect lives and property across different land tenures. The plans take into account the requirements of specific land tenures, such as forests, farms, parks and private property, and have been completed for the major fire districts in NSW (Williams et al. 2001).

NPWS is also developing a NSW version of the CSIRO National Plant Fire Response Register. This database collates fire response, life history, habitat and distributional data, allowing species to be placed in appropriate functional groups for management purposes.

The RFS, NPWS and State Forests of NSW contribute financially, as well as in-kind, to the recently established Cooperative Research Centre for Bushfire Research, which has been funded for a seven-year period. Of particular interest is Project B, which will investigate the impact of fire on biodiversity and incorporate data from major NSW fire research projects, such as the Eden Burn Study.

Effectiveness of responses

Management of fire regimes has been contentious for decades, and this has been intensified by the recent drought and resulting extreme fire events. There is still considerable debate about the level of hazard reduction burning required in NSW and agreement has not yet been reached on the characteristics of a sustainable fire management regime.

Future directions

Individuals, and business and land managers should continue to adapt and learn to live with natural fire regimes. This includes the need to locate and design structures and use building materials that are appropriate for natural fire regimes.

Further research is needed to explore possible new models of living, with fire as are continuing efforts to reduce bushfire risk and ensure properties are prepared for the fire season.

Linked issues

2.1 Population and settlement patterns

4.2 Soil erosion

5.3 Surface water quality

6.1 Terrestrial ecosystems

6.3 Terrestrial species diversity