6.5 Fire

Fire is a significant and ongoing threat to human settlement and ecosystem integrity. An understanding of the role of fire regimes in ecological systems is increasingly being factored into decision-making.

Altered fire regimes since human settlement (too much or too little fire, or fire of too high or too low an intensity) can have major detrimental effects on the structure of most ecosystems and the populations of many endangered species.

Fire is a natural part of the Australian landscape. Getting the balance right between the need to preserve natural ecosystems and ensuring community safety and the protection of assets is the key to appropriate fire regimes.

One of the key components in managing fire is hazard-reduction burning, but appropriate levels for this practice still attract debate in the public arena.

NSW indicators

Introduction

Fire has been present on the Australian continent for millions of years and is a key factor in plant and animal population dynamics in most ecological communities in NSW. Many Australian animals and plants have evolved not only to survive, but also to benefit from the effects of fire. A substantial proportion of the NSW flora depends on fire to assist in reproductive processes.

In Australia, fire has been managed since the earliest human presence. Although the fire regimes practised by Aboriginal people before European arrival are not fully understood by the scientific community, it is evident that the pattern of fire in the landscape has changed in the past 200 years (Williams et al. 2001). The introduction of individual property ownership and the need to protect stock and assets has altered fire regimes across a variety of landscapes in NSW.

Current status and trends

Incidence of fire

Bushfires possess immense destructive force and may result in substantial social costs, including the loss of human lives, buildings, infrastructure and livestock. In extreme cases, such as the Canberra bushfires of 2003, they result in natural disasters that claim human lives, inflict broad destruction on human assets across the landscape, and disrupt essential services. The effects of fires in NSW are conventionally reported in terms of their extent and social impacts and costs.

The incidence of fire varies greatly from year to year (Table 6.10). The number of fires is most closely linked to prevailing weather patterns and, in particular, the occurrence of extreme fire conditions, best indicated by the number of statewide fire bans declared in a fire season. Fire bans are declared locally or statewide by the NSW Rural Fire Service (RFS) when the fire risk is severe during extreme hot, dry and windy conditions.

Table 6.10: Bushfires and damage during the 2002–05 fire seasons

Source: RFS 2005

Notes: ^(a) This number is derived by adding the number of fires from the four RFS Regions. It should be noted that any fire that occurred across the boundary of two regions would have been counted twice.

^(b) Section 44 declarations apply to fires where the RFS Commissioner controls operations.

The primary factors determining the severity and extent of bushfires are wind speed, temperature and humidity. Contributing factors include the available fuel load, the physical structure of vegetation and the degree of dryness. The effectiveness of fire suppression actions also determines the extent and severity of running fires.

Fire ecology

While the impact of bushfires is commonly reported in terms of areas burnt and lives and assets lost, this is an insufficient basis to determine their ecological effects, which depend on fire intensity, season and previous fire history. Understanding the ecological outcomes of fire is further impeded by a poor knowledge of the response of fauna to fire.

Ecological communities are dynamic systems where fire is just one of the natural disturbances that brings change. Fires shape the structure, composition and function of most plant communities, creating specific habitats required by a range of species. When fires occur too frequently, even fire-tolerant species may become locally extinct. Conversely, the exclusion of fire may suppress the reproduction of fire-dependent species, also leading to local extinctions.

Altered fire regimes have been described as a threat to over 80% of the State's vegetation classes (see Biodiversity 6.1). Changes in fire patterns can cause a shift from one vegetation type to another and decrease habitat resilience to invasive species. High-frequency fire has been identified as a significant cause of biodiversity loss in NSW and is listed as a key threatening process under the Threatened Species Conservation Act 1995 (TSC Act).

The interval between fire events is a critical factor in the capacity of individual species to survive and reproduce (Bradstock & Kenny 2003). Minimum fire intervals have been developed for the maintenance of biodiversity, providing sufficient time for adequate seed to be produced (Table 6.11). However, some areas require fuel loads to be reduced more frequently to achieve fire management objectives (specifically the strategic fire advantage zones identified in bushfire risk management plans). Table 6.11 also provides maximum fire intervals for vegetation formations which serve as a general guide to their longer term requirements for fire.

Table 6.11: Fire intervals for NSW vegetation formations

Source: DEC data December 2005

Note: ^(a) These intervals are absolute minimums with respect to maintaining biodiversity as they provide little or no buffer for adequate seed production.

The frequency of prescribed burning appropriate for various vegetation classes in NSW is likely to remain the subject of scientific investigation for some time, in part due to the diverse array of species and communities and the length of time required to assess the long-term impacts of fire. However, the greatest biodiversity is maintained by varying the length of inter-fire intervals spatially and temporally within the specified range (Kenny et al. 2003).

Fire regimes

The emphasis of fire management should be on hazard reduction and minimising risk (Ellis et al. 2004). The primary objective of fire management by all agencies is to protect human life and property, with biodiversity conservation an important, but secondary consideration. While not necessarily mutually exclusive, these objectives require a compromise in establishing appropriate fire management regimes, which may result in sub-optimal outcomes for biodiversity conservation (DEC 2005).

Hazard-reduction burning to reduce fuel loads outside the peak fire season is a key fire management tool practised widely across the State. This is complemented by other key measures, such as community education and mechanical works to maintain setbacks around assets, strategic firebreaks and fire trails.

Fire and climate change

The incidence of wildfire is influenced by fire-weather risk, which is expected to rise as a result of climate change. A recent study projects the likely increase in fire-weather risk across regions of NSW (Hennessy et al. 2006). The frequency of days with very high and extreme ratings on the Forest Fire Danger Index were predicted to increase by 4–25% by 2020, and 15–70% by 2050, depending on the location. The predicted increase in fire-weather risk was greater at inland locations.

Causes of fire

During the 2003–05 fire seasons, the incidence of fire was markedly higher in densely populated areas along the NSW coast compared with larger but less densely populated areas elsewhere (Table 6.12). There appears to be a strong relationship between the incidence of fire and population density.

Table 6.12: Incidence of wild fire in NSW rural fire regions

Source: RFS 2005

Note: ^(a) Fires refers to bushfires only. Grass fires are excluded.

Data on the causes of fire from both the RFS and the National Parks and Wildlife Service (NPWS) indicates that most fires are not natural, but of human causation. The majority of fires are due to arson, accidental ignition or escapes from prescribed burn-offs, with arson the most common cause.

Investigations by the Australian Institute of Criminology into the causes of 466 fires between 2001 and 2004, using RFS data, found that 64% were deliberately lit. Data from NPWS supports this pattern, with almost half of the fires started in national parks during 2003–04 attributed to arson (Table 6.13).

Table 6.13: Causes of investigated bushfires in NSW

Sources: AIC 2005a; AIC 2005b; DEC 2005

Response to the issue

Under the Rural Fires Act 1997, the RFS is responsible for the prevention, mitigation and suppression of bushfires within rural fire districts. All functions performed by the RFS are required to be consistent with the principles of biodiversity conservation and ecological integrity stipulated by the Protection of the Environment Administration Act 1991.

To coordinate bushfire prevention and suppression, the RFS has established bushfire management committees which prepare bushfire risk management plans and operations coordination plans for each rural fire district. The risk-management plans specify a range of hazard-reduction strategies appropriate for the protection of the assets at risk from wild fire, including environmental assets. Operations coordination plans establish guidelines for coordinated firefighting and contain environmentally based restrictions. Operations maps also include provision for the consideration of environmental assets during firefighting operations.

The Bush Fire Environmental Assessment Code provides a framework for the environmental assessment and approval of bushfire hazard reduction works. Environmental assessments consider the impacts of prescribed burning and mechanical works on natural values, including vegetation, threatened species and heritage items, as well as their effects on soil stability, air and water pollution. Minimum fire intervals (see Table 6.11) are a critical component of environmental assessments. Outcomes of these assessments are used by the RFS and some other authorities for issuing bushfire hazard reduction certificates approving works and imposing conditions where appropriate.

In response to the 2001 Christmas bushfires, the Crimes Amendment (Bushfires) Act 2002 was passed, adding the new offence of lighting bushfires to the Crimes Act 1900. A range of measures has been implemented to reduce the rate of arson in NSW. While some strategies, such as educational programs for school students and the thorough screening of volunteer firefighters are designed to prevent the crime, others focus on developing better investigative techniques so that more arsonists will be apprehended.

The RFS coordinates the Firewise program in conjunction with other government agencies and stakeholders. This program provides on-ground advice and support for at-risk groups and is a key component of the hazard management program. Although the focus of the program is on protection of life and property, advice on environmental issues is also discussed.

Integrating bushfire protection into the planning system through the Planning for Bushfire Protection framework will ensure safer developments in bushfire-prone areas. A key approach is the consideration during the planning phase of setbacks around dwellings to provide protection from bushfires. Proposed developments may be re-sited if the environmental impacts of these setbacks are likely to be significant. Adoption of higher building construction standards may also be used to offset the distance required for setbacks.

The RFS maintains the Bushfire Risk Information Management System (BRIMS). Data is provided by the RFS, NPWS, and Forests NSW. BRIMS provides a vital resource for the storage of data on fires across the State. Long-term data on where fires start and how they spread will be invaluable for determining fire management strategies, including the allocation of firefighting resources, and the prevention of arson and accidental ignitions. Collated data on prescribed burns will also provide insight into the effect of fire history both operationally and from an environmental impact perspective. Only three years of data has been included to date so the full potential of the database has yet to be realised.

Future directions

The incidence of high fire-risk days – and consequently the frequency of wild fire – is expected to rise due to climate change. The number of days when it is safe to conduct hazard-reduction burning may also be reduced. The impact on biodiversity of drier conditions, more frequent wild fires and reduced opportunities for hazard-reduction burning need to be factored into the development of appropriate fire management techniques.

Fire management strategies will increasingly be based on better knowledge of fire behaviour and ecology, and better techniques for fire suppression. This will enable us to counteract, to some extent, the effects of climate change.

Fire patterns have generally been approached as a natural response by fire to unnatural fire management regimes. Evidence is now emerging that, particularly near more populated areas, the pattern of fire is largely not of natural causes. The incidence of arson and knowledge of the behavioural patterns of arsonists should be incorporated into fire management strategies.

It is imperative that new and ongoing research into all aspects of fire behaviour and ecology, and fire management and suppression is supported to enhance our capacity for living with fire.

There is considerable scope for better maintenance and use of the data and information that is collected about fire, and more could be collected. Alignment of data held by agencies is desirable to improve the consistency of figures reported. Information could be used more effectively, leading to more sophisticated analyses of wild fire patterns and effects, and particularly in decision-support and related applications for fighting fires, managing hazards and associated environmental impacts.