How does climate change affect wildfires?

Climate change is increasing the frequency and severity of wildfires in many regions, both directly by favouring meteorological conditions compatible with large wildfires and indirectly through cascading effects on ecosystems and societies. While most wildfires are initiated accidentally or intentionally by human activity – over 95% of wildfires across Southern and Central Europe are caused by humans[1] – climate change is significantly exacerbating their severity. The summer of 2022 in Europe witnessed the second worst wildfire season on record (after 2017), with wildfires seen in 45 countries and a total burnt area equivalent to the size of Montenegro.[2] Fires also broke out in several parts of England, after it experienced the warmest summer on record and the driest since July 1935.[3]

Globally, the length of fire seasons has increased 20% over the last four decades. Furthermore, about 60% of burnable areas experience more fire-prone climate due to more frequent and longer droughts, higher temperatures and stronger winds.[4] [5] This is leading to more intense and synchronized wildfires at a regional level as well as the emergence of mega-fires, defined as fire events above 10,000 hectares.[6]

Additionally, there is some evidence that climate change is increasing the total amount of vegetation and thus the amount of wildfire ‘fuel’ (any substance that can burn), for example by inducing tree mortality or stimulating growths during warmer winters. However, these effects are less understood.[7]

Human activity can play an important role in alleviating the impact of climate change on wildfires through effective fuel management, fire prevention and suppression measures.[8]

References

[1] Ganteaume, A., Camia, A., Jappiot, M., San-Miguel-Ayanz, J., Long-Fournel, M., Lampin, C., 2013. A Review of the Main Driving Factors of Forest Fire Ignition Over Europe. Environmental Management 51, 651–662. https://doi.org/10.1007/s00267-012-9961-z

[2] European Commission, 2023. The EU 2022 wildfire season was the second worst on record [WWW Document]. URL https://joint-research-centre.ec.europa.eu/jrc-news-and-updates/eu-2022-wildfire-season-was-second-worst-record-2023-05-02_en  (accessed 6.15.23).

[3] Goodier, M., 2023. Record number of serious outdoor fires tackled in England in summer 2022. The Guardian.

[4] Abatzoglou, J.T., Williams, A.P., Barbero, R., 2019. Global Emergence of Anthropogenic Climate Change in Fire Weather Indices. Geophys. Res. Lett. 46, 326–336. https://doi.org/10.1029/2018GL080959

[5] Jolly, W.M., Cochrane, M.A., Freeborn, P.H., Holden, Z.A., Brown, T.J., Williamson, G.J., Bowman, D.M.J.S., 2015. Climate-induced variations in global wildfire danger from 1979 to 2013. Nat Commun 6, 7537. https://doi.org/10.1038/ncomms8537

[6] Linley, G.D., Jolly, C.J., Doherty, T.S., Geary, W.L., Armenteras, D., Belcher, C.M., Bliege Bird, R., Duane, A., Fletcher, M., Giorgis, M.A., Haslem, A., Jones, G.M., Kelly, L.T., Lee, C.K.F., Nolan, R.H., Parr, C.L., Pausas, J.G., Price, J.N., Regos, A., Ritchie, E.G., Ruffault, J., Williamson, G.J., Wu, Q., Nimmo, D.G., Poulter, B., 2022. What do you mean, ‘megafire’? Global Ecol Biogeogr 31, 1906–1922. https://doi.org/10.1111/geb.13499

[7] Harris, R.M.B., Remenyi, T.A., Williamson, G.J., Bindoff, N.L., Bowman, D.M.J.S., 2016. Climate–vegetation–fire interactions and feedbacks: trivial detail or major barrier to projecting the future of the Earth system? WIREs Clim Change 7, 910–931. https://doi.org/10.1002/wcc.428

[8] Jones, Matthew W., John T. Abatzoglou, Sander Veraverbeke, Niels Andela, Gitta Lasslop, Matthias Forkel, Adam J. P. Smith, et al. 2022. Global and Regional Trends and Drivers of Fire Under Climate Change. Reviews of Geophysics 60 (3). https://doi.org/10.1029/2020RG000726. 

Wildfires can have significant impacts on human health and the economy, as well as on the climate and the environment.

Extreme fire events can have significant material and human costs. In particular, mega-fires and multiple fires concentrated in one region can overwhelm firefighting efforts and increase the risk of damages and severe outcomes. A recent example is the 2017 Pedrógão Grande fires in Portugal, which caused extensive damages exceeding 200 million euros and 66 fatalities.[1]

Wildfire smoke exposure is a serious public health issue that majorly contributes to ambient air pollution and increases respiratory morbidity and cardiovascular diseases.[2] [3] Wildfires can release large amounts of Fine Particulate Matter (PM2.5), which is particularly harmful to public health due to its ability to penetrate deeply into the lungs. It can also travel great distances from the fire site[4] [5] as observed during the Canadian wildfires in June 2023, where smoke travelled to New York City, qualifying it as having the worst air quality in the world at the time.[6]

Wildfires are also a significant source of greenhouse gas (GHG) emissions. For example, in 2019, the Flow Country fires doubled the GHG emissions of Scotland in only a couple of days and record-breaking wildfires in Canada released about 1.5 times the annual emissions of the UK over the first six months of 2023. Additionally, rapid temperature rise in the Arctic, and associated damages to the permafrost and drying of the vegetation, are leading to an increase in Arctic fires. Most fires in the Arctic burn underground and form ‘zombie fires,’ which can last for several years and are particularly hard to detect and extinguish.[7] These fires emit large quantities of carbon, accumulated in Arctic soils over millennia, which could lead to the emission of 544 megatons of carbon in 2100, compared to about 143 megatons currently. They also have further impacts on permafrost and other indirect impacts on climate.[8] Overall, fires (including controlled ones) currently emit around 2 gigatons of carbon every year globally (about 5% of total GHG emissions), although three-quarters of these emissions are recaptured during post-fire vegetation regrowth.[9]

The impact of wildfires on ecosystems depends on the specific vulnerability of the ecosystem and the intensity of the burns. Some ecosystems, such as tropical rainforests, can prove extremely vulnerable to fires and even low-intensity wildfires could lead to important tree mortality and radical changes in ecosystem composition.[10] Fire-prone ecosystems, such as savannas, are dependent on fire disturbance for some essential functions such as the regeneration of some plants species, but can be negatively affected by change in the fire regime's characteristics, such as increased intensity of the fires or changes in seasonality.[11] Wildfires also have a significant impact on wildlife, due to smoke exposure and resulting impacts on respiratory health and behaviours, destruction of habitats, displacement, exposure to predators, and stress.[12]

References:

[1] Ribeiro, L.M., Rodrigues, A., Lucas, D., Viegas, D.X., 2020. The Impact on Structures of the Pedrógão Grande Fire Complex in June 2017 (Portugal). Fire 3, 57. https://doi.org/10.3390/fire3040057

[2] Chen, H., Samet, J.M., Bromberg, P.A., Tong, H., 2021. Cardiovascular health impacts of wildfire smoke exposure. Part Fibre Toxicol 18, 2. https://doi.org/10.1186/s12989-020-00394-8

[3] Reid, C.E., Brauer, M., Johnston, F.H., Jerrett, M., Balmes, J.R., Elliott, C.T., 2016. Critical Review of Health Impacts of Wildfire Smoke Exposure. Environ Health Perspect 124, 1334–1343. https://doi.org/10.1289/ehp.1409277

[4] Naeher, L.P., Brauer, M., Lipsett, M., Zelikoff, J.T., Simpson, C.D., Koenig, J.Q., Smith, K.R., 2007. Woodsmoke Health Effects: A Review. Inhalation Toxicology 19, 67–106. https://doi.org/10.1080/08958370600985875 

[5] Xing, Y.-F., Xu, Y.-H., Shi, M.-H., Lian, Y.-X., 2016. The impact of PM2.5 on the human respiratory system. Journal of Thoracic Disease 8.

[6] Chaffin, J., Campbell, C., Williams, A., 2023. Wildfire smoke makes New York air quality worst in the world. Financial Times.

[7] McCarty, J.L., Smith, T.E.L., Turetsky, M.R., 2020. Arctic fires re-emerging. Nat. Geosci. 13, 658–660. https://doi.org/10.1038/s41561-020-00645-5

[8] Lin, S., Liu, Y., Huang, X., 2021. Climate-induced Arctic-boreal peatland fire and carbon loss in the 21st century. Science of The Total Environment 796, 148924. https://doi.org/10.1016/j.scitotenv.2021.148924

[9] Van Der Werf, G.R., Randerson, J.T., Giglio, L., Van Leeuwen, T.T., Chen, Y., Rogers, B.M., Mu, M., Van Marle, M.J.E., Morton, D.C., Collatz, G.J., Yokelson, R.J., Kasibhatla, P.S., 2017. Global fire emissions estimates during 1997–2016. Earth Syst. Sci. Data 9, 697–720. https://doi.org/10.5194/essd-9-697-2017

[10] Balch, J.K., Brando, P.M., Nepstad, D.C., Coe, M.T., Silvério, D., Massad, T.J., Davidson, E.A., Lefebvre, P., Oliveira-Santos, C., Rocha, W., Cury, R.T.S., Parsons, A., Carvalho, K.S., 2015. The Susceptibility of Southeastern Amazon Forests to Fire: Insights from a Large-Scale Burn Experiment. BioScience 65, 893–905. https://doi.org/10.1093/biosci/biv106

[11] Keeley, J.E., 2009. Fire intensity, fire severity and burn severity: a brief review and suggested usage. Int. J. Wildland Fire 18, 116. https://doi.org/10.1071/WF07049

[12] Garcês, A., Pires, I., 2023. The Hell of Wildfires: The Impact on Wildlife and Its Conservation and the Role of the Veterinarian. Conservation 3, 96–108. https://doi.org/10.3390/conservation3010009

Globally, current policies have revolved around extinguishing and controlling wildfires, rather than proactive prevention.  However, research has shown that these approaches often fail to address the complex social and ecological process driving wildfires, linked to factors such as rural abandonment and lack of vegetation management, which could result in increasing the risk of extreme fire events.[1]

For example, criminalization of fire use and changes in economic incentives resulted in the decline of traditional controlled fires use by smallholders around the world. Most of the time this was without alternative practices to limit vegetation buildup, further increasing the risks of intense wildfires[2]. In England, a ban on prescribed fires on blanket bogs has been adopted, even though there is mixed evidence regarding the impact of this practice on biodiversity, carbon storage and wildfire prevention.[3] [4]

In some jurisdictions, there has been a move towards integrated fire management – a holistic approach aimed at alleviating destructive wildfires and maintaining desirable fire regimes. This approach consists of five phases: review and analysis, wildfire risks reductions, readiness, response and recovery.[5] Integrated fire management is seen as more effective as it addresses upstream causes of wildfires, such as fuel accumulation or lack of awareness with economically realistic options, which can increase the resilience of landscape to fire in the long-term.[6] For example, across the Global South, traditional landholders in savanna regions are increasingly recognized as essential actors in fire management, through their extensive fire management knowledge and their use of fires to reduce fuel load and wildfire risks.[7] [8]

Climate change will increase the intensity and frequency of wildfires over the coming decades and record-breaking fire seasons will become increasingly common across the globe, including in regions that have experienced few fires until now. Urban areas close to nature are the areas exposed to the highest risks of materials and human damage. Thus, in these areas, urban planning, structural design and choice of materials need to consider fire risks, and effective fuel management and evacuation strategies need to be developed.[9] [10] Nature-based solutions to climate change, such as forest landscape restoration, must also account for mitigation and adaptation to wildfire risks for sequestrating carbon and yielding biodiversity benefits on long-term.[11] 

Moreover, there is a pressing need for multi-disciplinary and long-term research on fire ecology and management, as well as a need to involve scientists, policymakers and fire management stakeholders in these research efforts. Moving away from operating in silos and reducing the science-policy divide will help facilitate more effective and fair wildfire management policies.[12] [13]

Key resources for policymakers

• EFFIS portal: Provides fire danger forecasts, maps of fuels and other drivers of wildfires regimes, map of recent burns and other useful data.
• What can we do differently about the extreme wildfire problem: An overview: A book chapter providing an introduction to Shared Wildfires Governance – an alternative to the fire suppression approach.
• PyroLife blog: A European Union funded PhD training programme for fire scientists, which has many useful blog posts on integrated fire management.
• Leverhulme Centre for Wildfires, Environment and Society: news about fires research in UK and abroad, regular events and contact of UK-based fires researchers.

References:

[1] Xanthopoulos, G., Leone, V., Delogu, G.M., 2020. The suppression model fragilities, in: Extreme Wildfire Events and Disasters. Elsevier, pp. 135–153. https://doi.org/10.1016/B978-0-12-815721-3.00007-2

[2] Smith, C., Perkins, O., Mistry, J., 2022. Global decline in subsistence-oriented and smallholder fire use. Nat Sustain 5, 542–551. https://doi.org/10.1038/s41893-022-00867-y

[3] Heinemeyer, A., Thomas, D.S.G., Pateman, R., 2023. Restoration of heather-dominated blanket bog vegetation for biodiversity, carbon storage, greenhouse gas emissions and water regulation. Comparing burning to alternative mowing and uncut management. 10 year report. University of York. https://doi.org/10.15124/YAO-2WTG-KB53

[4] Holland, J.P., Pollock, M., Buckingham, S., Glendinning, J., McCracken, D., 2022. Reviewing, assessing and critiquing the evidence base on the impacts of muirburn on wildfire prevention, carbon storage and biodiversity (No. 1302). NaturScot.

[5] United Nations Environment Programme, 2022. Spreading like Wildfire—The Rising Threat of Extraordinary Landscape Fires.

[6] Wollstein, K., Creutzburg, M.K., Dunn, C., Johnson, D.D., O’Connor, C., Boyd, C.S., 2022. Toward integrated fire management to promote ecosystem resilience. Rangelands 44, 227–234. https://doi.org/10.1016/j.rala.2022.01.001

[7] Eloy, L., A. Bilbao, B., Mistry, J., Schmidt, I.B., 2019. From fire suppression to fire management: Advances and resistances to changes in fire policy in the savannas of Brazil and Venezuela. Geogr J 185, 10–22. https://doi.org/10.1111/geoj.12245 

[8] Nikolakis, W., Welham, C., Greene, G., 2022. Diffusion of indigenous fire management and carbon-credit programs: Opportunities and challenges for “scaling-up” to temperate ecosystems. Front. For. Glob. Change 5, 967653. https://doi.org/10.3389/ffgc.2022.967653

[9] Dossi, S., Messerschmidt, B., Ribeiro, L.M., Almeida, M., Rein, G., 2022. Relationships between building features and wildfire damage in California, USA and Pedrógão Grande, Portugal. Int. J. Wildland Fire 32, 296–312. https://doi.org/10.1071/WF22095

[10] Moritz, M.A., Batllori, E., Bradstock, R.A., Gill, A.M., Handmer, J., Hessburg, P.F., Leonard, J., McCaffrey, S., Odion, D.C., Schoennagel, T., Syphard, A.D., 2014. Learning to coexist with wildfire. Nature 515, 58–66. https://doi.org/10.1038/nature13946

[11] Lindenmayer, D.B., Bowd, E.J., Gibbons, P., 2023. Forest restoration in a time of fire: perspectives from tall, wet eucalypt forests subject to stand-replacing wildfires. Phil. Trans. R. Soc. B 378, 20210082. https://doi.org/10.1098/rstb.2021.0082

[12] Aguilar, S., Montiel, C., 2011. The challenge of applying governance and sustainable development to wildland fire management in Southern Europe. Journal of Forestry Research 22, 627–639. https://doi.org/10.1007/s11676-011-0168-6

[13] Moritz, M.A., Batllori, E., Bradstock, R.A., Gill, A.M., Handmer, J., Hessburg, P.F., Leonard, J., McCaffrey, S., Odion, D.C., Schoennagel, T., Syphard, A.D., 2014. Learning to coexist with wildfire. Nature 515, 58–66. https://doi.org/10.1038/nature13946

There are significant knowledge gaps in our understanding of wildfires. For example, scientists know that extreme fire events can change size and direction suddenly, due to heat convection and smoke plumes.[1] However, these processes are still poorly understood, reducing our ability to predict wildfires’ behaviour to plan firefighting and evacuation efforts and reduce societal costs.[2] [3]

Additionally, scientists do not fully understand how ecosystems recover from and adapt to wildfires, which is important for developing fire management strategies fitted to the local ecosystems.[4]

Our understanding of human impacts is also incomplete. Current fire models have been developed with limited data on human use of fire and have a simplistic representation of human influence on wildfires.[5] Multidisciplinary research projects, wider availability of data on the use of fires adapted to quantitative analysis and coupling of different types of models can help scientists better understand future fires regimes and how they interact with societal changes.[6]

References:

[1] Duane, A., Castellnou, M., Brotons, L., 2021. Towards a comprehensive look at global drivers of novel extreme wildfire events. Climatic Change 165, 43. https://doi.org/10.1007/s10584-021-03066-4

[2] Castellnou, M., et. al., 2018. Fire growth patterns in the 2017 mega fire episode of October 15, central Portugal, in: Advances in Forest Fire Research 2018. Imprensa da Universidade de Coimbra, pp. 447–453. https://doi.org/10.14195/978-989-26-16-506_48

[3] Duane, A., Castellnou, M., Brotons, L., 2021. Towards a comprehensive look at global drivers of novel extreme wildfire events. Climatic Change 165, 43. https://doi.org/10.1007/s10584-021-03066-4

[4] Harris, R.M.B., Remenyi, T.A., Williamson, G.J., Bindoff, N.L., Bowman, D.M.J.S., 2016. Climate–vegetation–fire interactions and feedbacks: trivial detail or major barrier to projecting the future of the Earth system? WIREs Clim Change 7, 910–931. https://doi.org/10.1002/wcc.428

[5] Ford, A.E.S., Harrison, S.P., Kountouris, Y., Millington, J.D.A., Mistry, J., Perkins, O., Rabin, S.S., Rein, G., Schreckenberg, K., Smith, C., Smith, T.E.L., Yadav, K., 2021. Modelling Human-Fire Interactions: Combining Alternative Perspectives and Approaches. Front. Environ. Sci. 9, 649835. https://doi.org/10.3389/fenvs.2021.649835

[6] Ford, A.E.S., Harrison, S.P., Kountouris, Y., Millington, J.D.A., Mistry, J., Perkins, O., Rabin, S.S., Rein, G., Schreckenberg, K., Smith, C., Smith, T.E.L., Yadav, K., 2021. Modelling Human-Fire Interactions: Combining Alternative Perspectives and Approaches. Front. Environ. Sci. 9, 649835. https://doi.org/10.3389/fenvs.2021.649835