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Fire impacts on biodiversity

From John Woinarski, 1998 Summary Papers from the North Australia Fire Management Workshop, March 24–25, Darwin, eds. Tropical Savannas CRC.

The issues | Effects of changed fire equilibrium |Unravelling impact of fire |Managing fire for conservation |

Golden-shouldered parrot: studies have revealed the bird has an intricate relationship with fire
Photo: Darryn Storch

The issues

Essentially, there are two questions:

  • what species (or environments) are being disadvantaged by the prevailing fire regimes?
  • (how) can we mould those regimes to offer better protection for these losers?

Effects of changed fire equilibrium

An intricate and relatively ordered fire regime imposed on northern Australia over the period 50,000+ years before the present to around 50 years ago, has undoubtedly sifted the biota, retaining only those species and environments tolerant of that regime. Rapid and substantial changes in burning practice over the course of this century have upset the previous equilibrium, making conditions more favourable for some species (and environments) and less favourable for others. Depending upon the geographic scale and magnitude of the shift, the disadvantaged species (and environments) face local decline to regional extinction.

Unravelling impact of fire

Describing and mapping the contemporary pattern of fires in northern Australia is relatively straightforward, notwithstanding the technological sophistication required. But how can these patterns be translated to tell us of the ecological consequences? Conceptually, it is such a simple thing to detect which species are declining because of now inappropriate fire regimes. Practically it is a far more complex problem. Compared to most other areas in the world, there is very limited historical documentation of the distribution and abundance of the biota in northern Australia. Landscape-scale changes here have involved a complex interplay of factors, so that disentangling the impacts of fire from those of, say, pastoralism is difficult, and may be unhelpful (given the sometimes synergistic effects). The impacts of fire upon any element of biodiversity are also extremely variable, differing with extent, timing, intensity and frequency.

Managing fire for conservation

For most species and many environments, the management of fire for conservation of biodiversity is hampered by lack of knowledge. There have been few long-term experimental studies capable of revealing sustained responses to fire regimes. Most of these have involved experimental plots which are too small to detect changes for most vertebrates (the notable exception being CSIRO's catchment-scale study at Kapalga); and/or the dead hand of experimental protocol has led to the imposition of unrealistically regimented fire treatments.

A few studies have chronicled long-term changes in the distribution of particular environments through matching of a chronological sequence of imagery and/or through comparison with historical records. A few studies have focussed on individual species (e.g. Callitris, golden-shouldered parrot, frilled lizard). These studies have revealed some strong and intricate relationships with fire, but the more general extension of these findings to other species and environments remains very uncertain.

Lacking information (but not abandoning the need for more of it), is it possible to work from general principles? Maintaining biodiversity is largely about maximising environmental heterogeneity. More than almost any other factor which can affect landscape patchiness, fire is a flexible tool, and fire management should aim to impose a gamut of regimes (other than the unreasonably extreme) across most of the landscape, at an appropriate scale. With a little winkling, this can be translated into four guidelines:

  • fires should be small.
  • fires should be planned.
  • fires should happen.
  • fire regimes should be heterogeneous.