The 2019–20 wildfires in eastern Australia presented a globally important opportunity to evaluate the respective roles of climatic drivers and natural and anthropogenic disturbances in causing high-severity fires. Here, we show the overwhelming dominance of fire weather in causing complete scorch or consumption of forest canopies in natural and plantation forests in three regions across the geographic range of these fires. Sampling 32% (2.35 Mha) of the area burnt we found that >44% of the native forests suffered severe canopy damage. Past logging and wildfire disturbance in natural forests had a very low effect on severe canopy damage, reflecting the limited extent logged in the last 25 years (4.5% in eastern Victoria, 5.3% in southern New South Wales (NSW) and 7.8% in northern NSW). The most important variables determining severe canopy damage were broad spatial factors (mostly topographic) followed by fire weather. Timber plantations affected by fire were concentrated in NSW and 26% were burnt by the fires and >70% of the NSW plantations suffered severe canopy damage showing that this intensive means of wood production is extremely vulnerable to wildfire. The massive geographic scale and severity of these Australian fires is best explained by extrinsic factors: an historically anomalous drought coupled with strong, hot dry westerly winds that caused uninterrupted, and often dangerous, fire weather over the entire fire season.
Subscribe to Journal
Get full journal access for 1 year
only $9.92 per issue
All prices are NET prices.
VAT will be added later in the checkout.
Tax calculation will be finalised during checkout.
Rent or Buy article
Get time limited or full article access on ReadCube.
All prices are NET prices.
Satellite-based fire severity mapping based on Sentinel-2 satellite imagery38 was obtained for the Victorian fires from the Victorian Department of Environment, Land, Water and Planning and is available on the Victoria government spatial data portal (https://discover.data.vic.gov.au/dataset/fire-severity-map-of-the-major-fires-in-gippsland-and-north-east-victoria-in-2019-20-version-1-). Severity classes were calculated for the NSW fires using the fire extent and severity algorithm (FESM) developed by Gibson et al.39 and are available on the NSW SEED data portal (https://datasets.seed.nsw.gov.au/dataset/fire-extent-and-severity-mapping-fesm). Forest harvest date for Victoria was obtained from the Victorian Department of Environment, Land, Water and Planning and is available on the Victoria government spatial data portal (https://discover.data.vic.gov.au/dataset/logging-history-overlay-of-most-recent-harvesting-activities). Forest harvest date for NSW was obtained from NSW Forestry Corp on request, with data for older age classes within NSW supplemented with statewide land cover and trees study (SLATS) data provided by NSW Department of Planning, Industry and Environment. The 2017 NSW Landuse mapping was obtained from the NSW seed data portal (https://datasets.seed.nsw.gov.au/dataset/nsw-landuse-2017-v1p2-f0ed). Fire history and fire progression isochrons were obtained from the Victorian Department of Environment, Land, Water and Planning (https://discover.data.vic.gov.au/dataset/fire-history-overlay-of-most-recent-fires) and were provided by the NSW Rural Fire Service for NSW. Gridded FFDI data are available from the Bureau of Meteorology60. TPI was calculated from the NASA Shuttle Radar Topography Mission 90-m digital elevation model with a window of 250 m (ref. 62). Vegetation type was derived from the National Vegetation Inventory System 4.1 (https://data.gov.au/data/dataset/57c8ee5c-43e5-4e9c-9e41-fd5012536374) for Victoria and from the state vegetation formation dataset for NSW (https://www.environment.nsw.gov.au/research/Visclassification.htm).
Code for the analyses is available on FigShare at the following URL: https://figshare.com/articles/software/Drivers_of_the_Severity_and_Extent_of_2019_20_Australian_Fires_and_Forest_Management_-_Data_and_Code/14331530.
Bowman, D. M. J. S. et al. Fire in the Earth system. Science 324, 481–484 (2009).
Davis, K. T. et al. Wildfires and climate change push low-elevation forests across a critical climate threshold for tree regeneration. Proc. Natl Acad. Sci. USA 116, 6193–6198 (2019).
Enright, N. J., Fontaine, J. B., Bowman, D. M. J. S., Bradstock, R. A. & Williams, R. J. Interval squeeze: altered fire regimes and demographic responses interact to threaten woody species persistence as climate changes. Front. Ecol. Environ. 13, 265–272 (2015).
Abatzoglou, J. T. & Williams, A. P. Impact of anthropogenic climate change on wildfire across western US forests. Proc. Natl Acad. Sci. USA 113, 11770–11775 (2016).
Bowman, D. M. J. S. et al. Vegetation fires in the Anthropocene. Nat. Rev. Earth Environ. 1, 500–515 (2020).
Keeley, J. E., van Mantgem, P. & Falk, D. A. Fire, climate and changing forests. Nat. Plants 5, 774–775 (2019).
Lindenmayer, D. B., Kooyman, R. M., Taylor, C., Ward, M. & Watson, J. E. Recent Australian wildfires made worse by logging and associated forest management. Nat. Ecol. Evol. 4, 898–900 (2020).
Murphy, B. P. et al. Fire regimes of Australia: a pyrogeographic model system. J. Biogeogr. 40, 1048–1058 (2013).
Poulos, H. M., Barton, A. M., Slingsby, J. A. & Bowman, D. M. J. S. Do mixed fire regimes shape plant flammability and post-fire recovery strategies? Fire 1, 39 (2018).
Cawson, J. G. et al. Exploring the key drivers of forest flammability in wet eucalypt forests using expert-derived conceptual models. Landsc. Ecol. 35, 1775–1798 (2020).
Thomas, P. B., Watson, P. J., Bradstock, R. A., Penman, T. D. & Price, O. Modelling surface fine fuel dynamics across climate gradients in eucalypt forests of south‐eastern Australia. Ecography 37, 827–837 (2014).
Bennett, L. T. et al. Mortality and recruitment of fire-tolerant eucalypts as influenced by wildfire severity and recent prescribed fire. For. Ecol. Manag. 380, 107–117 (2016).
Fairman, T. A., Bennett, L. T., Tupper, S. & Nitschke, C. R. Frequent wildfires erode tree persistence and alter stand structure and initial composition of a fire‐tolerant sub‐alpine forest. J. Veg. Sci. 28, 1151–1165 (2017).
Prior, L. D., Williamson, G. J. & Bowman, D. M. J. S. Impact of high-severity fire in a Tasmanian dry eucalypt forest. Aust. J. Bot. 64, 193–205 (2016).
Bassett, O. D., Prior, L. D., Slijkerman, C. M., Jamieson, D. & Bowman, D. M. J. S. Aerial sowing stopped the loss of alpine ash (Eucalyptus delegatensis) forests burnt by three short-interval fires in the Alpine National Park, Victoria, Australia. For. Ecol. Manag. 342, 39–48 (2015).
Bowman, D. et al. Wildfires: Australia needs national monitoring agency. Nature 584, 188–191 (2020).
King, A. D., Pitman, A. J., Henley, B. J., Ukkola, A. M. & Brown, J. R. The role of climate variability in Australian drought. Nat. Clim. Change 10, 177–179 (2020).
Sharples, J. J. et al. Natural hazards in Australia: extreme bushfire. Clim. Change 139, 85–99 (2016).
Bowman, D. M. J. S., Williamson, G. J., Price, O. F., Ndalila, M. N. & Bradstock, R. A. Australian forests, megafires and the risk of dwindling carbon stocks. Plant, Cell Environ. 44, 347–355 (2020).
Khaykin, S. et al. The 2019/20 Australian wildfires generated a persistent smoke-charged vortex rising up to 35 km altitude. Commun. Earth Environ. 1, 22 (2020).
Borchers Arriagada, N. et al. Unprecedented smoke-related health burden associated with the 2019–20 bushfires in eastern Australia. Med. J. Aust. 213, 282–283 (2020).
Johnston, F. H. et al. Unprecedented health costs of smoke-related PM2.5 from the 2019–20 Australian megafires. Nat. Sustain. 4, 42–47 (2021).
Ward, M. et al. Impact of 2019–2020 mega-fires on Australian fauna habitat. Nat. Ecol. Evol. 4, 1321–1326 (2020).
Bowman, D. M. J. S., Williamson, G. J., Prior, L. D. & Murphy, B. P. The relative importance of intrinsic and extrinsic factors in the decline of obligate seeder forests. Glob. Ecol. Biogeogr. 25, 1166–1172 (2016).
Povak, N. A., Kane, V. R., Collins, B. M., Lydersen, J. M. & Kane, J. T. Multi-scaled drivers of severity patterns vary across land ownerships for the 2013 Rim Fire, California. Landsc. Ecol. 35, 293–318 (2020).
Parks, S. A. et al. High-severity fire: evaluating its key drivers and mapping its probability across western US forests. Environ. Res. Lett. 13, 044037 (2018).
Fang, L., Yang, J., Zu, J., Li, G. & Zhang, J. Quantifying influences and relative importance of fire weather, topography, and vegetation on fire size and fire severity in a Chinese boreal forest landscape. For. Ecol. Manag. 356, 2–12 (2015).
Thompson, J. R. & Spies, T. A. Vegetation and weather explain variation in crown damage within a large mixed-severity wildfire. For. Ecol. Manag. 258, 1684–1694 (2009).
Stephens, S. L. et al. Fire and climate change: conserving seasonally dry forests is still possible. Front. Ecol. Environ. 18, 354–360 (2020).
Dieleman, C. M. et al. Wildfire combustion and carbon stocks in the southern Canadian boreal forest: implications for a warming world. Glob. Change Biol. 26, 6062–6079 (2020).
Nolan, R. H. et al. Causes and consequences of eastern Australia’s 2019–20 season of mega‐fires. Glob. Change Biol. 26, 1039–1041 (2020).
Boer, M. M., Resco de Dios, V. & Bradstock, R. A. Unprecedented burn area of Australian mega forest fires. Nat. Clim. Change 10, 171–172 (2020).
van Oldenborgh, G. J. et al. Attribution of the Australian bushfire risk to anthropogenic climate change. Nat. Hazards Earth Syst. Sci. 21, 941–960 (2021).
Adams, M. A., Shadmanroodposhti, M. & Neumann, M. Letter to the Editor. Causes and consequences of Eastern Australia’s 2019‐20 season of mega‐fires: a broader perspective. Glob. Change Biol. 26, 3756–3758 (2020).
Lindenmayer, D. B. & Taylor, C. New spatial analyses of Australian wildfires highlight the need for new fire, resource, and conservation policies. Proc. Natl Acad. Sci. USA 117, 12481–12485 (2020).
Lindenmayer, D. B., Hobbs, R. J., Likens, G. E., Krebs, C. J. & Banks, S. C. Newly discovered landscape traps produce regime shifts in wet forests. Proc. Natl Acad. Sci. USA 108, 15887–15891 (2011).
Taylor, C., McCarthy, M. A. & Lindenmayer, D. B. Nonlinear effects of stand age on fire severity. Conserv. Lett. 7, 355–370 (2014).
Collins, L., Griffioen, P., Newell, G. & Mellor, A. The utility of Random Forests for wildfire severity mapping. Remote Sens. Environ. 216, 374–384 (2018).
Gibson, R., Danaher, T., Hehir, W. & Collins, L. A remote sensing approach to mapping fire severity in south-eastern Australia using sentinel 2 and random forest. Remote Sens. Environ. 240, 111702 (2020).
Collins, L., Bradstock, R. & Penman, T. Can precipitation influence landscape controls on wildfire severity? A case study within temperate eucalypt forests of south-eastern Australia. Int. J. Wildland Fire 23, 9–20 (2014).
Price, O. F. & Bradstock, R. A. 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. Manag. 113, 146–157 (2012).
Storey, M., Price, O. & Tasker, E. The role of weather, past fire and topography in crown fire occurrence in eastern Australia. Int. J. Wildland Fire 25, 1048–1060 (2016).
Bradstock, R. A., Hammill, K. A., Collins, L. & Price, O. Effects of weather, fuel and terrain on fire severity in topographically diverse landscapes of south-eastern Australia. Landsc. Ecol. 25, 607–619 (2010).
Taylor, C., Blanchard, W. & Lindenmayer, D. B. Does forest thinning reduce fire severity in Australian eucalypt forests? Conserv. Lett. https://doi.org/10.1111/conl.12766 (2020).
Lydersen, J. M. et al. Evidence of fuels management and fire weather influencing fire severity in an extreme fire event. Ecol. Appl. 27, 2013–2030 (2017).
Gómez-González, S., Ojeda, F. & Fernandes, P. M. Portugal and Chile: longing for sustainable forestry while rising from the ashes. Environ. Sci. Policy 81, 104–107 (2018).
Bowman, D. M. J. S. et al. Human–environmental drivers and impacts of the globally extreme 2017 Chilean fires. Ambio 48, 350–362 (2019).
Jackson, W. Fire, air, water and earth–an elemental ecology of Tasmania. Proc. Ecol. Soc. Aust. 3, 9–16 (1968).
Tolhurst, K. G. & McCarthy, G. Effect of prescribed burning on wildfire severity: a landscape-scale case study from the 2003 fires in Victoria. Aust. For. 79, 1–14 (2016).
Gammage, B. The Biggest Estate on Earth: How Aborigines Made Australia (Allen & Unwin, 2011).
Dargavel, J. Views and perspectives: why does Australia have ‘forest wars’? Int. Rev. Environ. Hist. 4, 33–51 (2018).
Kanowski, P. J. Australia’s forests: contested past, tenure-driven present, uncertain future. For. Policy Econ. 77, 56–68 (2017).
Australian Forest and Wood Products Statistics Mar-Jun 2019 (Australian Bureau of Agricultural and Resource Economics and Sciences, 2019).
Ferguson, I. Australian plantations: mixed signals ahead. Int. For. Rev. 16, 160–171 (2014).
Raison, R. & Squire, R. Forest Management in Australia: Implications for Carbon Budgets Technical Report 32 (Australian Greenhouse Office, 2008).
Proctor, E. & McCarthy, G. Changes in fuel hazard following thinning operations in mixed-species forests in East Gippsland, Victoria. Aust. For. 78, 195–206 (2015).
NSW Regional Forest Agreements Assessment of Matters Pertaining to Renewal of Regional Forest Agreements (NSW Department of Primary Industries, 2018).
Evans, J. spatialEco_. R package version 1.3-1 https://github.com/jeffreyevans/spatialEco (2020).
Farr, T. G. et al. The shuttle radar topography mission. Rev. Geophys. https://doi.org/10.1029/2005RG000183 (2007).
Dowdy, A. J. Climatological variability of fire weather in Australia. J. Appl. Meteorol. Climatol. 57, 221–234 (2018).
Hodges, J. S. & Reich, B. J. Adding spatially-correlated errors can mess up the fixed effect you love. Am. Stat. 64, 325–334 (2010).
Rabus, B., Eineder, M., Roth, A. & Bamler, R. The shuttle radar topography mission—a new class of digital elevation models acquired by spaceborne radar. ISPRS J. Photogramm. Remote Sens. 57, 241–262 (2003).
Kuhn, M. et al. caret: Classification and regression training. R package version 6.0-77 (2018).
De Reu, J. et al. Application of the topographic position index to heterogeneous landscapes. Geomorphology 186, 39–49 (2013).
We thank the New South Wales Government’s Department of Planning, Industry & Environment for providing funds to support this research via the NSW Bushfire Risk Management Research Hub.
The authors declare no competing interests.
Peer review information Nature Ecology & Evolution thanks the anonymous reviewers for their contribution to the peer review of this work.
Publisher’s note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
Extended Data Fig. 1 Marginal effect of topographic position index (TPI) in fire severity for the three study regions.
Marginal effect of topographic position index (TPI) in fire severity for the three study regions.
About this article
Cite this article
Bowman, D.M.J.S., Williamson, G.J., Gibson, R.K. et al. The severity and extent of the Australia 2019–20 Eucalyptus forest fires are not the legacy of forest management. Nat Ecol Evol 5, 1003–1010 (2021). https://doi.org/10.1038/s41559-021-01464-6