Underpinnings of fire management for biodiversity conservation in ...

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Tracks and fire suppression
What is considered to be enough for a track network is likely to be perceived very differently in
different regions. In sparsely settled, western New South Wales, after the extensive 1974–75 fires,
the need was expressed in the following way: ‘a system of firebreaks [i.e. fuel breaks] would have
to be constructed to enable ready access for fire fighters and to be used as a basis for back-burning
operations’. A ‘huge firebreak system’ was inaugurated with blocks of approximately 32 000 ha
each (Bushfire Council of NSW, extract, 1970s). Blocks of this size, with woody fire-prone vegetation,
would not be tolerated, or likely to occur now, near the edges of cities.
Creating a track network can have adverse environmental impacts. In itself, a track network will not
stop all fires. However, the efficacy of a track network for fire suppression can be improved to an
extent, dependent on the capacity and efficacy of suppression forces available, along with local fuel
treatments. The use of aircraft could decrease the density of track networks perceived to be necessary
for fire management. There is no one simple answer, but perhaps many partial answers, to the quest
for the ideal system of tracks for fire suppression within a biodiversity management context. Cost,
suppression capacity, fire fighter safety, environmental effects, weather, vegetation, fuel treatments
(see next chapter), proximity to economic assets and terrain will all influence the outcome. Biodiversity
conservation is rarely the sole aim of management. It usually occurs alongside others for water supply,
recreation, cultural conservation and utilities. Tracks of one type or another are inevitable in moderateand
large-sized reserves, where various assets are threatened by fire occurrences.
Real world situations
It could be argued that all present systems have limited effectiveness where extreme fire weather
and continuous fuels occur. Experience during the multiple fires of 2003 in south-eastern Australia
in three jurisdictions at the same time (Victoria, NSW and ACT) suggests that the best aerial and
ground suppression resources currently available will not be sufficient to stop a fire during extreme
weather. However, in the absence of a track network, suppression system and fuel-modification
program (considered in the next chapter), the situation could be worse. These three components –
tracks, suppression capacity and fuel modification – need to be considered together, not separately,
and an appreciation of their combined effectiveness sought to achieve economic-asset-protection
and biodiversity-conservation objectives. Subsumed in the ‘track’ part of this consideration will be
fire fighter safety, cost of installation and maintenance of the network, ease of burning out fuels
(suppression tactics) and environmental effects (Table 2.4).
In real terrain, which is often mountainous and forested, the creation of track networks will not only
be constrained by the issues raised above, but also by environmental matters – some in relation to
the effects of the tracks, but others simply as a matter of cost effectiveness. For example, mountain
ranges are often aligned in a particular direction with more or less parallel ridges and valleys. Spurs
may run down into valleys from ridge lines at sharp angles, demarcating ever-widening catchments.
Plateaux, cliffs and gorges may occur in places. Geological substrates may vary, affecting soil type and
erosion potential, along with slope angle and length. Fuel arrays may be diverse. However, tracks will
tend to favour ridge lines for economic, environmental and scenic reasons. River or gorge crossings
requiring bridges will be avoided, cliffs will be impassable and valley lines may be subject to flooding,
thick vegetation and narrow, steep upper reaches. Yet wide grassy valleys may be the best place to
suppress fires, rather than on ridge tops with woody fuels. Temporary perimeter tracks can sometimes
be butted onto drainage lines, rather than directed down steep wooded spurs. However, proximity to
drainage lines may increase the chance of erosion and sedimentation, and therefore the disturbance
of water supplies to cities and local communities. Ridges and upper slopes may be the best places for
prescribed burning to take place from tracks because there ridges typically have drier fuels and fires
can be ignited such that they travel against the slope and achieve only low intensities.
Ever present in the conservation manager’s mind may be the effects of the tracks on rare and
threatened plants and animals, feral animals and weeds, cultural sites, water quality and quantity,
disease organisms, unwanted ignitions and passive control of fires entering the area – as well as
suppression considerations.
Fire and adaptive management Underpinnings of fire management for biodiversity conservation in reserves