This is the last Letter written expressly for the ACT Bush Fire Council. In this and the previous series of Letters the author has tried to illustrate the extent of the issues associated with bushfires in Australia. It seemed appropriate to return to a favourite theme for this last word: “Can we create a suitable language that reflects a robust understanding of our subject?”.Can we avoid half-truths, myths, misnomers and tautologies? As we learn, how can we convey new knowledge effectively if we do not adjust our language?

Words are actually models – short cuts, abbreviations, pictures, caricatures, symbols – of reality. If we use wrong or imprecise words we can convey wrong or ambiguous images, even wrong concepts, which can perpetuate unrealistic expectations in our peers, and in the public at large, and so hold back the development of the subject.

There is reason to think that for lack of a [precise] vocabulary the birth of physics may have been delayed for at least a century” (Taylor 1941 p.12).

Lying at the foundation of the scientific method is the necessity for sharp definition of terms” (Taylor 1941, p.11). Can we define words more clearly?

Wrong, misleading or imprecise words and terms

‘Wildfire’: the term ‘unplanned fire’ removes the impression that all fires are ‘wild’, of high intensity.

‘Cool fires’; ‘low-intensity fires’ is more appropriate.

‘Fuel is a hazard’: ‘fuel’ is combustible material; a fire burning the fuel can be a ‘hazard’ – cause injury or harm - to something or someone.

‘Fire break’: a ‘fire break’ does not necessarily cause a break in the spread of a fire but ‘fuel breakis a break in the continuity of the fuel.

‘Containment line’ and ‘control line’: these ‘lines’ do not always contain or control the fire but may give the impression that they always do so; ‘fuel break’ seems more appropriate.

Misapplied terms

‘Fire scar’ is correct usage when applied to an organism like a tree but not when it is applied to images of recently burned areas on aerial photos or satellite images: ‘scar’ implies ‘damage’ which may or may not become permanent. ‘Damage’ implies the existence of assessment criteria, a value system. The presence of fire on a landscape is not necessarily ‘damaging’. Therefore, some neutral term like ‘fire footprint’ is better.

‘Fuel’ is used correctly when referring to live or dead material potentially ignitable by adjacent burning material. ‘Available fuel’ is usually measured as the potentially-dry litter, less than 6mm in diameter, found on the forest floor. Yet, it is true that forest materials like shrub canopies and tree crowns can also burn (i.e. are ‘fuel’), albeit under certain more extreme weather, slope and forest-structural conditions. Specialists will note in this case that the ‘available fuel’ has increased but many people will not see it this way. ‘Available fuel’ can be a shorthand term which is misleading if it is used in the public arena, especially, and without qualification.

‘Fire intensity’ is sometimes used when ‘fire severity’ is meant. ‘Fire intensity’ is the rate of heat release from a portion of the fire perimeter; it is a property of a portion of a fire perimeter. ‘Fire severity’ is used to describe the effect of a fire on a tree, plant community etc. In other words a fire has an intensity which may induce a severity class like ‘scorched’ or ‘defoliated’ as a result of its passage. For a discussion of the confusion in terms see Feller (1998).

Half truths and slogans

‘The flora is adapted to fire’: this is an incomplete statement; rather the flora in a particular area is adapted to certain fire regimes – combinations of type of fire (i.e. in peat or above-ground only), fire intensity, season of burn and between-fire interval. Because the flora in an area is adapted to certain fire regimes, by definition it is not adapted to others (Gill 1975).

‘Grazing prevents blazing’: as was the case for fire regimes this statement needs amplification. Grazing regimes – type of animal, intensity of grazing, seasonality and interval - can affect fuel load and condition and may or may not affect ‘blazing’. There is a brief discussion of this in Esplin et al. (2003).

‘Pyrodiversity promotes biodiversity’: Not any ‘pyrodiversity’ will promote all biodiversity (see the incomplete statement ‘the flora is adapted to fire’ above). Rather, appropriate fire regimes can help maintain local biodiversity – see Martin and Sapsis (1991).


Needless repetition occurs in some fire terms: ‘fuel-reduction burning’ is the most common perhaps. Can burning take place without reducing fuel? ‘Burning for fuel reduction’ is clearer. “Prescribed burning for ...’ may be even better.

Myths and folklore (from Cheney and Sullivan 1997)

‘Asphyxiation will occur in a fire’; this is not true of bushfires, apparently, because flames will go out before oxygen levels are too low to sustain breathing ( p.82).

‘Green grass burns faster’; this is illusory (p. 85).

‘Fires can spread faster than a speeding car’ or “bullet”; this is an illusion also (p.89).

To achieve a precise vocabulary that expresses concepts clearly is a significant challenge. It is a challenge that we should confront regularly.


Cheney, P. and Sullivan, A. (1997). Grassfires. Fuel, Weather and Fire Behaviour. CSIRO Publishing, Collingwood.

Esplin, B., Gill, A.M. and Enright, N. (2003). Report of the Inquiry into the 2002-2003 Victorian Bushfires. State Government of Victoria, Melbourne. 370p.

Feller, M.C. (1998). The influence of fire severity, not fire intensity, on understorey vegetation biomass in British Columbia. In: 13th Fire and Forestry Meteorology Conference, Lorne, Australia 1996. Pp. 335-348. International Association of Wildland Fire, Moran, Wyoming, USA.

Gill, A.M. (1975). Fire and the Australian flora: a review. Australian Forestry 38, 4-25.

Martin, R.E. and Sapsis, D.B. (1991). Fires as agents of biodiversity: pyrodiversity promotes biodiversity. Proceedings of the Symposium on Biodiversity of Northwestern California October 28-30, 1991, Santa Rosa, California. Pp. 150-157

Taylor, L.W. (1941). Physics.The Pioneer Science. Volume 1. Mechanics .. Heat ..Sound. Dover, New York.


The support of members of the Act Bush Fire Council in producing these Letters has been greatly appreciated. The Letters have been distributed locally by Pat Barling of the ACT Volunteer Brigades Association and to more distant parts by Bob Conroy, NSW National Parks and Wildlife Service, and Rhonda Melzer of the Queensland National Parks and Wildlife Service. To all of you, my thanks.

A. Malcolm Gill
26 June 2004