Ecological effects of wildfire foams and retardants in Australia James Stewart

1
Ecological effects of wildfire foams and
retardants in AustraliaJames Stewart
2
Summary

• Introduction
• Australian soil characteristics and floristic
  adaptations
• Fire fighting chemical types
• Australian Studies
• Conclusion

3
Introduction

• Fire fighting chemicals have been used in Aus for
  approx 30 yrs, worldwide 35yrs
• Environmental effects of fire retardants have
  been of concern since the 1970s
• Average of 120,000 l/yr of fire retardant
  chemicals used in Vic, Aus

4
Introduction

• Firefighting chemicals used in Australia have
  been tested and approved by the United States
  Department of Agriculture for effects on the
  environment.
• As a result, no separate or further toxicological
  assessment is required for registration in
  Australia, therefore, it is endorsed by the
  Australasian Fire Authorities Council
• In Australia, large numbers of species are
  endemic, many are rare.
• Many of the sclerophyllous plant families such as
  Epacridaceae, Proteaceous, and Myrtaceae are not
  represented in the North American flora

5
Australian soil characteristics and floristic
adaptations

• Most Aus soils are based upon sedimentary rock
• Naturally low in P along with N
• P determines flora spp. distribution
• Aus flora able redistribute P
• Aus flora respond negatively to extra P

6
Fire fighting chemicals

• Two general types of fire control chemicals
• Long-term fire retardants
• Remain effective after the water has evaporated
• Short-term fire retardants
• Depend on the water they contain to suppress the
  fire

7
Fire fightingchemicals

• Long-Term Fire Retardants
• Are typically fertilizer salts which are mixed
  with water to ensure uniform dispersal.
• Commonly used long-term retardants are mixtures
  of diammonium sulphate, diammonium phosphate,
  monoammonium phosphate-gum thickeners, iron
  oxide-colouring agent, and preservatives
• Usually by aerial application

8
Fire fighting chemicals

• Particularly useful in slowing the spread of
  fires in remote, inaccessible terrain as well as
  in controlling spot fires, allowing time for the
  construction of control lines
• Form a non-combustible barrier after the
  evaporation of the water
• The ammonium salts chemically combine with
  cellulose as the fuels are heated, effectively
  removing the fuel from combustion

9
Fire fighting chemicals

• Short-Term Retardants
• Injected into the water as it is pumped out, the
  nozzle aerates it, forming a frothy mixture.
• Contain surfactants, foaming, and wetting agents,
  which
• Reduce surface tension
• Increases the ability of water to spread over the
  fuel and penetrate into the fuel
• Reduce the rate of water evaporation and drainage
• Insulated from fuels from heat
• Reduced contact from air

10
Australian Studies

• Long term retardant tested on Euc vegetation in
  Blue Mountains, NSW
• Resulted in Euc leaf death within a week of
  treatment, which continued for many months, but
  no tree mortality
• Understorey shrubs
• Mortality in two spp.
• Decreases in cover for 19 of 45 spp.
• Ability to survive and recover is probably a
  function of individual spp. characteristics

Dodonaea triquetra (Large-leaf hop-bush)
Acacia longifolia (Sallow Wattle)
11
Australian Studies

• DSE, VIC, applied Phos-Chek D75-R to 2 heathland
  communities which are naturally low in soil
  nutrients, esp. P
• To determine on the effect on vegetation,
  surface-active invertebrates, and soil chemistry
• Soil chemistry
• pH decreased by up to 0.5 units
• N and S content increased and decreased back to
  normal levels within 12 months
• After 12 months, the P content was still 5 times
  above normal levels

12
Australian Studies

• Vegetation
• No significantly change species composition or
  projected foliage
• Caused whole plant or shoot death in some and
  increased the shoot growth within other
  Allocasuarina, Banksia and Leptospermum spp.
• Provided an environment more conducive to weed
  invasion
• May potentially increased the growth rates of
  native grasses and sedge
• Surface-active invertebrates
• Normally recover within two or three years to
  pre-fire levels
• There were no detectable retardant-related
  changes in the short-term

13
Australian Studies

• Unintentional aerial application of long-term
  fire-fighting chemicals onto two small streams
  during a natural wildfire event on Kangaroo
  Island, SA,
• Provided an opportunity to study the short-term
  effects on water chemistry and aquatic
  invertebrates.
• 2 weeks, samples of water and macroinvertebrates
  were collected upstream, within and below
  application site
• Three sites on a reference stream in the same
  sub-catchment that had been burned by the same
  fire but without application of fire-suppressants
  were also sampled.
• All sites were resampled three months later

14
Australian Studies

• Each stream differed in taxon richness and
  composition
• Taxon richness was often higher at the middle and
  lower sites on the two impacted streams
• Whereas there was no significant difference among
  sites on the reference stream
• Reasoning for this could be environmental
  conditions in the isolated pools of Australian
  temporary streams are often severe especially
  where high salinity reduces the amount of
  dissolved oxygen available.
• Lack of effect of fire-suppressant foams on
  macroinvertebrates may partly result from their
  inherent high tolerance to the harsh physical and
  chemical conditions of these streams

15
Conclusion

• All projects acknowledged the limitations, short
  comings of individual projects involved and
  validity of results, these include
• Increasing studies to more long-term (2 3
  years)
• Well-defined experimental design and rigorous
  sample techniques to provide more ecologically
  and physiologically meaningful data sets
• Sample size
• Further glasshouse trails to investigate specific
  response of flora to fighting chemicals

16
Conclusion

• External influences may have been factor in the
  outcome of results such as
• Seasonal conditions
• Salinity
• Insect herbivory
• Rainfall
• Safety measures denied immediate access to fire
  impact site

17

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