Few of us are aware that for a number of years the firefighting agencies in Victoria (CFA, Parks Victoria, DNRE) have been using a range of fire fighting chemicals to combat fire in addition to good old water.
Even fewer of us are aware of the potential ecological consequences of using chemicals to retard or extinguish fires, and it's no longer acceptable for the fire fighting agencies to simply fob us off with "trust us, we're the professionals, and we'll only do what is best!" Some chemicals give a very positive advantage in firefighting, others need to be used with care.
Retardants are basically fertilizers (ammonium phosphate and ammonium sulphate) - you may use them on your garden if you're not a strict organic gardener - and they contain high levels of nitrogen, phosphorus and sulphur. Parks Victoria and DNRE, but not the CFA, use retardants on a regular basis. The potential problem with these chemicals is that in ecosystems which have developed on low nutrient soils such as heaths and dry sclerophyll forests, the input of these nutrients, especially phosphorus and nitrogen, can irreversibly change the composition of the vegetation.
Retardants don't appear to have any effects on birds or mammals, but because retardants are mostly dropped from planes or helicopters, they have the potential to contaminate creeks, rivers, dams, swamps etc. Of course, there are guidelines to minimize this, but accidents do happen! If the retardants enter aquatic systems then fish and aquatic invertebrates are at risk, and there are few studies (and none in Australia) to indicate how long term the impacts are.
Class A foams have really only begun to be used extensively in Australia in the last few years. They are essentially detergents, or wetting agents, without any fertilizer content. They are of particular interest to us living in urban fringe bushland, because the CFA has started to supply Class A foams to many of the tankers that regularly turn out to the fires in our area. They can be applied either by air or from a "normal" hose off a tanker. Like retardants, Class A foams are also a real problem if they enter aquatic systems, but they do not seem to have short or long term effects on birds or mammals, nor do they seem to have any negative influence on native plant species.
Recent trials carried out at Deakin University, where foam was applied (at the concentrations used to fight fires) to a range of plants species (eucalypt, banksia, wattle, tussock grass, native peas), the plants showed no change in any of the growth indicators measured. This is a very encouraging result! Foams are so efficient at suppressing the spread of fires, that there is great potential for using it to create short term firebreaks for carrying out ecological burning, as well as putting out bushfires. At present, we generally use rake hoe trails to contain prescribed fires, but these cause quite severe damage to the soil, and a non damaging, easy to apply alternative could greatly expand the possibilities for applying prescribed fire for ecological (and fuel reduction) purposes.
 Foam being applied to eucalypt seedlings. |
 Eucalyptus polyanthemosseedlings after application of foam. The seedlings on the left are untreated, those on the right have had foam applied. |