Image: Phil Zylstra
Hot Topic

Mitigating fire risk through prescribed burning

Friday, 5 March 2021  | 

Authors: Philip Gibbons, ANU (philip.gibbons@anu.edu.au); Phil Zylstra, Curtin University (Philip.Zylstra@curtin.edu.au)

Prescribed burning is done primarily to protect built assets by increasing fire frequency under controlled conditions [1,7,12]. This is intended to reduce fire risk by reducing the amount of leaf litter and vegetation, and may be called ‘hazard reduction burning’ if effective.

When and how can prescribed burning mitigate fire risk? Studies across SW and SE Australia indicate that very recent prescribed burns (within 1-6 years depending on the ecosystem) can make a bushfire easier to control [2,6,10,12] and if undertaken close to structures such as houses, can reduce the likelihood that they are destroyed during a bushfire [14,25,26,27]. Prescribed burns rarely stop fires by themselves, but they may be helpful if conducted in places where fire crews or residents can fight fires directly [26].

When is prescribed burning ineffective? Prescribed burns become less effective as the weather becomes more severe [12,27,34]. Burning can also make a range of forest ecosystems more flammable after the first few years have passed post-burning [10, 40]. Increased flammability occurs if fires have stimulated plant growth close to the ground, or reduced the cover of taller plants by scorching or killing them, thereby creating a drier, windier environment.  Prescribed burning can therefore make some landscapes more flammable if it is not limited to intensive treatment areas which are frequently burnt.

What other options are available for hazard reduction? The risk of house loss during bushfires is reduced when houses are set back from adjacent native vegetation, adjacent vegetation is greener, or is separated into discrete patches [13,14]. Mechanical methods such as cutting of grass and shrubs can be used in intensively managed areas, and fire should be aggressively suppressed in those forests that become less flammable over time, to allow them to reach maturity [10, 40]. Bushfire hazard cannot, however, be eliminated with prescribed burning or other methods of hazard reduction so other strategies such as building designs with greater fire resilience and early evacuation to safer places should be part of the fire plan for anyone in a bushfire-prone area [14].

A downloadable pdf on this Hot Topic can be found here.

 

Supporting Research

Title
Aims
[1] AFAC. (2017) National Guidelines for Prescribed Burning Strategic and Program Planning – National Burning Project sub-project 4. Australasian Fire and Emergency Service Authorities Council Limited, East Melbourne, Victoria.
To provide national best-practice guidelines for prescribed burning.
[2] Boer M. M., Sadler R. J., Wittkuhn R. S., McCaw W. L. & Grierson P. F. (2009) Long-term impacts of prescribed burning on regional extent and incidence of wildfires—Evidence from 50 years of active fire management in SW Australian forests. For. Ecol. Manage. 259 , 132–142. [online]. Available from: http://linkinghub.elsevier.com/retrieve/pii/S0378112709007294 [Accessed March 2, 2012].
To measure the effectiveness of prescribed burning for wildfire mitigation in the Warren bioregion
[3] Bowman D. M. J. S., Murphy B. P., Neyland D. L. J., Williamson G. J. & Prior L. D. (2014) Abrupt fire regime change may cause landscape-wide loss of mature obligate seeder forests. Glob. Chang. Biol. doi: 10.1111/gcb.12433. [online]. Available from: http://www.ncbi.nlm.nih.gov/pubmed/24132866 [Accessed January 22, 2014].
To test the vulnerability of E. delegatensis forests to ecosystem collapse
[4] Bradshaw S. D., Dixon K. W., Lambers H., Cross A. T., Bailey J. & Hopper S. D. (2018) Understanding the long-term impact of prescribed burning in mediterranean-climate biodiversity hotspots, with a focus on south-western Australia. Int. J. Wildl. Fire 27 , 643–657.
To summarise existing work on the efficacy and effects of prescribed burning in SW Australia, and to foreshadow its ecological impacts..
[5] Burrows N. D. (1999) Fire behaviour in Jarrah forest fuels. I: Laboratory experiments CALMScience 3 , 31–56.
To determine the relationship between the weight of jarrah surface litter and fire behaviour
[6] Burrows N. D. (1999) Fire behaviour in Jarrah forest fuels. II: Field experiments CALMScience 3 , 57–84.
To determine the relationship between the weight of jarrah surface litter and fire behaviour
[7] Burrows N. & McCaw L. (2013) Prescribed burning in southwestern Australian forests. Front. Ecol. Environ. 11, e25-e34.
To describe and analyse prescribed burning in SW Western Australia.
[8] Cheney N. P., Gould J. S., McCaw W. L. & Anderson W. R. (2012) Predicting fire behaviour in dry eucalypt forest in southern Australia. For. Ecol. Manage. doi: 10.1016/j.foreco.2012.06.012. [online]. Available from: http://dx.doi.org/10.1016/j.foreco.2012.06.012.
To build a model of fire behaviour in dry eucalypt forest using slected fuel descriptors
[9] Cui X., Alam M. A., Perry G. L. W., Paterson A. M., Wyse S. V & Curran T. J. (2019) Green firebreaks as a management tool for wildfires: Lessons from China. J. Environ. Manage. 233 , 329–336. [online]. Available from: https://linkinghub.elsevier.com/retrieve/pii/S0301479718314658.
To treview the extensive Chinese literature documenting the effectiveness of green fire breaks in China
[10] Dixon K. M., Cary G. J., Worboys G. L., Seddon J. & Gibbons P. (2018) A comparison of fuel hazard in recently burned and long-unburned forests and woodlands. Int. J. Wildl. Fire 27 , 609–622.
To examine the trends in an operational measure of fire risk (overall fuel hazard) in long-unburnt forests
[11] Fernandes P. A. M. (2015) Empirical support for the use of prescribed burning as a fuel treatment. Curr. For. Reports doi: 10.1007/s40725-015-0010-z. [online]. Available from: http://link.springer.com/10.1007/s40725-015-0010-z.
To document observational evidence supporting the value of prescribed burning
[12] Fernandes P. A. M. & Botelho H. S. (2003) A review of prescribed burning effectiveness in fire hazard reduction. Int. J. Wildl. Fire.
To document evidence of prescribed fire effectiveness
[13] Gibbons P., Gill A. M., Shore N., Moritz M. A., Dovers S. & Cary G. J. (2018) Options for reducing house-loss during wildfires without clearing trees and shrubs. Landsc. Urban Plan.
To quantify the protective value to houses afforded by fuel treatments other than tree and shrub clearance
[14] Gibbons P., van Bommel L., Gill A. M. et al. (2012) Land management practices associated with house loss in wildfires. PLoS One 7 , e29212. [online]. Available from: http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=3260958&tool=pmcentrez&rendertype=abstract [Accessed March 9, 2012].
To quantify the protective value to houses afforded by fuel treatments
[15] Gifford R. M. & Howden M. (2001) Vegetation thickening in an ecological perspective: Significance to national greenhouse gas inventories. Environ. Sci. Policy 4 , 59–72.
To summarise the drivers of vegetation thickening and their influence on the carbon balance
[16] Gosper C. R., Prober S. M. & Yates C. J. (2013) Multi-century changes in vegetation structure and fuel availability in fire-sensitive eucalypt woodlands. For. Ecol. Manage. doi: 10.1016/j.foreco.2013.08.005. [online]. Available from: http://dx.doi.org/10.1016/j.foreco.2013.08.005.
To measure long-term fuel dynamics in a semi-arid woodland
[17] Harrington G. N. & Sanderson K. D. (1994) Recent contraction of wet sclerophyll forest in the wet tropics of Queensland due to invasion by rainforest. Pacific Conserv. Biol. 1 , 319.
To measure rates and determine drivers of succession from tropical wet sclerophyll forest to rainforest.
[18] Haslem A., Kelly L. T., Nimmo D. G. et al. (2011) Habitat or fuel? Implications of long-term, post-fire dynamics for the development of key resources for fauna and fire. J. Appl. Ecol. 48 , 247–256.
To measure changes in habitat and fuel parameters in mallee woodland over a 110-year chronosequence.
[19] Jenkins M. E., Collins L., Price O. F. et al. (2016) Environmental values and fire hazard of eucalypt plantings. Ecosphere 7 , e01528.
To model the flammability of eucalypt plantations relative to surrounding pasture
[20] Kenny S. A., Bennett A. F., Clarke M. F. & Morgan J. W. (2018) Time-since-fire and climate interact to affect the structural recovery of an Australian semi-arid plant community. Austral Ecol. 43 , 456–469. [online]. Available from: http://doi.wiley.com/10.1111/aec.12582.
To measure long-term vegetation dynamics in a semi-arid woodland
[21] Kitzberger T., Aráoz E., Gowda J. H., Mermoz M. & Morales J. M. (2012) Decreases in fire spread probability with forest age promotes alternative community states, reduced resilience to climate variability and large fire regime shifts. Ecosystems 15 , 97–112.
To simulate the landscap effects of various forest ages with positive feedbacks
[22] Lindenmayer D. B., Hobbs R. J., Likens G. E., Krebs C. J. & Banks S. C. (2011) Newly discovered landscape traps produce regime shifts in wet forests. Proc. Natl. Acad. Sci. U. S. A. 108 , 15887–15891.
To describe and define the concept of a landscape trap, using E. regnans as an example
[23] McArthur A. G. (1967) Fire behaviour in Eucalypt forests. Forestry and Timber Bureau Leaflet 107. In: 9th Commonwealth Forestry Conference p. 26 Canberra, ACT.
To propose a model of fire behaviour
[24] McCaw W. L. (2013) Managing forest fuels using prescribed fire - A perspective from southern Australia. For. Ecol. Manage. doi: 10.1016/j.foreco.2012.09.012. [online]. Available from: http://dx.doi.org/10.1016/j.foreco.2012.09.012.
To summarise the theoretical and empirical arguments in support of prescribed fire
[25] Penman T. D., Bradstock R. & Price O. (2014) Reducing wildfire risk to urban developments: Simulation of cost-effective fuel treatment solutions in south eastern Australia. Environ. Model. Software 52, 166-75.
To identify the most cost-effective way to reduce risk to urban areas from wildfire
[26] Price O. F. & Bradstock R. A. (2010) The effect of fuel age on the spread of fire in sclerophyll forest in the Sydney region of Australia. Int. J. Wildland Fire 19, 35-45.
To examne the influence of fuel age on the extent of unplanned fire
[27] Price O. F. & Bradstock R. A. (2012) The efficacy of fuel treatment in mitigating property loss during wildfires: Insights from analysis of the severity of the catastrophic fires in 2009 in Victoria, Australia. J. Environ. Manage.
To examine the efficacy of various fuel treatments in mitigating fire severity and property loss from a major fire event.
[28] Price O. F., Pausas J. G. H., Govender N. et al. (2015) Global patterns in fire leverage: the response of annual area burnt to previous fire. Int. J. Wildl. Fire 24 , 297–306.
To catalogue leverage values from diverse forests across the globe, and determine whether leverage is proportional to the annual area burnt by wildfires.
[29] Price O. F., Penman T. D., Bradstock R. A., Boer M. M. & Clarke H. G. (2015) Biogeographical variation in the potential effectiveness of prescribed fire in south-east Australia. J. Biogeogr. 42 , 2234–2245. [online]. Available from: http://onlinelibrary.wiley.com/doi/10.1111/jbi.12579/full.
To explore biogeographical patterns in the efficacy of prescribed burning by calculating leverage
[30] Sneeuwjagt R. J. & Peet G. B. (1976) Forest fire behaviour tables for Western Australia. Forests Department Western Australia, Perth, Australia.
No research involved or evidence presented. The authors presented a series of tables defining rates of fire spread in some West Australian forest types.
[31] Sullivan A. L., Surawski N. C., Crawford D. et al. (2018) Effect of woody debris on the rate of spread of surface fires in forest fuels in a combustion wind tunnel. For. Ecol. Manage. 424 , 236–245. [online]. Available from: https://doi.org/10.1016/j.foreco.2018.04.039.
To empirically measure the effect of woody debris on rates of fire spread.
[32] Taylor C., McCarthy M. A. & Lindenmayer D. B. (2014) Nonlinear effects of stand age on fire severity. Conserv. Lett. 7 , 355–370. [online]. Available from: http://doi.wiley.com/10.1111/conl.12122 [Accessed October 30, 2014].
To measure the relationship between stand age and severity of the 2009 Black Saturday fires in E. regnans forest
[33] Tepley A. J., Veblen T. T., Perry G. L. W., Stewart G. H. & Naficy C. E. (2016) Positive feedbacks to fire-driven deforestation following human colonization of the South Island of New Zealand. Ecosystems 19 , 1325–1344.
To examine the fire-vegetation feedbacks that facilitated historic ecosystem collapse across New Zealand
[34] Tolhurst K. G. & McCarthy G. (2016) Effect of prescribed burning on wildfire severity: a landscape-scale case study from the 2003 fires in Victoria. Aust For 79, 1-14.
To examine the effects of prescribed burning on the severity of unplanned fires.
[35] Tiribelli F., Kitzberger T. & Morales J. M. (2018) Changes in vegetation structure and fuel characteristics along post-fire succession promote alternative stable states and positive fire-vegetation feedbacks. J. Veg. Sci. doi: 10.1111/jvs.12620. [online]. Available from: http://doi.wiley.com/10.1111/jvs.12620.
To characterise flammability feedbacks in fores vs. shrublands
[36] Tiribelli F., Morales J. M., Gowda J. H., Mermoz M. & Kitzberger T. (2018) Non-additive effects of alternative stable states on landscape flammability in NW Patagonia: Fire history and simulation modelling evidence. Int. J. Wildl. Fire doi: 10.1071/WF18073.
To determine whether landscape flammability was controlled by the dominant vegetation
[37] Tng D. Y. P., Murphy B. P., Weber E. et al. (2012) Humid tropical rain forest has expanded into eucalypt forest and savanna over the last 50 years. Ecol. Evol. 2 , 34–45. [online]. Available from: http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=3297176&tool=pmcentrez&rendertype=abstract%5Cn%3CGo to ISI%3E://WOS:000312442000003.
To quantify the rate of tropical rainforest expansion into wet sclerophyll forest, and predict future cover in the absence of fire.
[38] Wilson N., Cary G. J. & Gibbons P. (2018) Relationships between mature trees and fire fuel hazard in Australian forest. Int. J. Wildl. Fire.
To test for relationships between the cover of mature trees and understorey density
[39] Zylstra P. J. (2013) The historical influence of fire on the flammability of subalpine Snowgum forest and woodland. Vic. Nat. 130 , 232–239. [online]. Available from: http://ro.uow.edu.au/smhpapers/1332/.
To identify the long-term flammability dynamics in subalpine snowgum forest and woodland, and validate the predicted drivers
[40] Zylstra P. J. (2018) Flammability dynamics in the Australian Alps. Austral Ecol. 43 , 578–591. [online]. Available from: https://onlinelibrary.wiley.com/doi/abs/10.1111/aec.12594.
To identify the long-term flammability dynamics across a diverse range of forests in south-eastern Australia
[41] Zylstra P. J., Bradstock R. A., Bedward M. et al. (2016) Biophysical mechanistic modelling quantifies the effects of plant traits on fire severity: species, not surface fuel loads determine flame dimensions in eucalypt forests. PLoS One 11 , e0160715. [online]. Available from: http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0160715.
To quantify the biophysical drivers of fire behaviour and severity, combine these in a mechanistic model, and validate predictions against a diverse dataset.