The impact of compound drought and heatwave events on the unprecedented 2020 fire season in the Pantanal, Brazil
Authors: Libonati Renata , Geirinhas João L , Silva Patrícia S , Russo Ana , Rodrigues Julia A , Belem Liz B C , Nogueira Joana , Roque Fabio O , DaCamara Carlos C , Nunes Ana M B , Marengo Jose A , Trigo Ricardo M 
Published: March 2022

&lt;p&gt;The year of 2020 was characterised by an unprecedented fire season in Pantanal, the largest continuous tropical wetland, located in south-western Brazil. This event was the largest ever recorded over, at least, the last two decades, reaching an amount of 3.9 million ha and affecting 17 million vertebrates&lt;sup&gt;1,2&lt;/sup&gt;. Recent evidence points out that this event resulted from a complex interplay between human, landscape, and meteorological factors&lt;sup&gt;3,4&lt;/sup&gt;. Indeed, much of the Pantanal has been affected by severe dry conditions since 2019, with 2020&amp;#8217;s drought being the most extreme and widespread ever recorded in the last 70 years&lt;sup&gt;5,6&lt;/sup&gt;. The drought condition was maintained at record levels during most of the year of 2021, following the climate change scenarios expected for this region&lt;sup&gt;7&lt;/sup&gt;. Prior to this comprehensive assessment, the 2020&amp;#8217;s fire season has been analyzed at the univariate level of a single climate event, not considering the co-occurrence of extreme and persistent temperatures with soil dryness conditions. Here, we show that the influence of land&amp;#8211;atmosphere feedbacks contributed decisively to the simultaneous occurrence of dry and hot spells, exacerbating fire risk. These hot spells, with maximum temperatures 6 &amp;#186;C above-average were associated with the prevalence of the ideal synoptic conditions for strong atmospheric heating, large evaporation rates and precipitation deficits&lt;sup&gt;4&lt;/sup&gt;. We stress that more than half of the burned area during the fire season occurred during compound drought-heatwave conditions. The synergistic effect between fuel availability and weather-hydrological conditions was particularly acute in the vulnerable northern forested areas. These findings are relevant for integrated fire management in the Pantanal as well as within a broader context, as the driving mechanisms apply across other ecosystems, implying further efforts for monitoring and predicting such extreme events.&lt;/p&gt;&lt;p&gt;&amp;#160;&lt;/p&gt;&lt;p&gt;References&lt;/p&gt;&lt;p&gt;[1] Garcia, L.C, et al.. Record-breaking wildfires in the world&amp;#8217;s largest continuous tropical wetland: Integrative fire management is urgently needed for both biodiversity and humans. J. Environ. Manage. 2021, 293, 112870.&lt;/p&gt;&lt;p&gt;[2] Tomas, W. M., et al. Counting the dead: 17 million vertebrates directly killed by the 2020&amp;#8217;s wildfires in the Pantanal wetland, Brazil. Sci. Rep. accepted.&lt;/p&gt;&lt;p&gt;[3] Libonati, R.; et al. Rescue Brazil&amp;#8217;s burning Pantanal wetlands. Nature. 2020, 588, 217&amp;#8211;219.&lt;/p&gt;&lt;p&gt;[4] Libonati, R., et al. Assessing the role of compound drought and heatwave events on unprecedented 2020 wildfires in the Pantanal. Environmental Research Letters. 2022, 17, 1.&lt;/p&gt;&lt;p&gt;[5] Thielen, D., et al. The Pantanal under Siege&amp;#8212;On the Origin, Dynamics and Forecast of the Megadrought Severely Affecting the Largest Wetland in the World. Water. 2021, 13(21), 3034.&lt;/p&gt;&lt;p&gt;[6] Marengo, J.A., et al. Extreme Drought in the Brazilian Pantanal in 2019&amp;#8211;2020: Characterization, Causes, and Impacts. Front. Water. 2021, 0, 13.&lt;/p&gt;&lt;p&gt;[7] Gomes, G.D.; et al.. Projections of subcontinental changes in seasonal precipitation over the two major river basins in South America under an extreme climate scenario. Clim. Dyn. 2021, 1-23.&lt;/p&gt;&lt;p&gt;&lt;em&gt;&amp;#160;&lt;/em&gt;&lt;/p&gt;&lt;p&gt;&lt;em&gt;This work &lt;/em&gt;&lt;em&gt;was supported by &lt;/em&gt;&lt;em&gt;Project Rede Pantanal from the Ministry of Science, Technology and Innovations of Brazil (FINEP grant 01.20.0201.00). R.L. was supported by CNPq [grant 305159/2018&amp;#8211;6] and FAPERJ [grant E26/202.714/2019]&lt;/em&gt;&lt;/p&gt;