Tomás Carrasco, CR2 Climate Science Center researcher; René Garreaud, CR2 Deputy Director; Deniz Bozkurt, CR2 Associate Researcher; Martín Jacques, Principal Investigator; Aníbal Pauchard, Institute of Ecology and Biodiversity (IEB) researcher, University of Concepción professor.
Editor: José Barraza, CR2 Science Communication Specialist
Key Findings:
Research has revealed that during the mega-fires of the 2016-2017 and 2022-2023 seasons, unprecedented extreme temperatures exceeding 41°C were recorded across much of south-central Chile, resulting in low humidity and desiccation of vegetation and soil. The meteorological conditions that facilitated these temperatures and humidity levels also generated the Puelche wind, which caused further air warming, and southerly winds that propagated the fires. These atmospheric phenomena that transformed fires into mega-fires can be forecast, suggesting the implementation of warnings when temperatures exceed 40°C.
Forest fires generate negative impacts on human life and health, biodiversity, and economic activities within affected territories. In Chile, these events are predominantly human-caused (98.5%), whether intentional (36.6%) or accidental (58.2%) (Pozo et al., 2022). Fire propagation depends on fuel availability, landscape characteristics, and atmospheric conditions. Since the 1970s, south-central Chile has experienced rapid land-use change, where the replacement of native forests with exotic pine and eucalyptus plantations, combined with invasive exotic species, has created homogeneous landscapes that increase fire risk (Pauchard et al., 2008; González et al., 2011; Cóbar-Carranza et al., 2015).
Furthermore, rising temperatures and megadrought conditions have facilitated fire propagation, contributing to increased burned areas since 2010 (González et al. 2017).
Until 2016, the area burned per season (July to June of the following year) in south-central Chile fluctuated between 10,000 and 100,000 hectares (ha), averaging 40,000 ha. However, this average was substantially exceeded during the 2016-2017 and 2022-2023 fire seasons, which resulted in unprecedented, burned areas exceeding 500,000 and 400,000 ha, respectively. The majority of this burned area occurred during the respective summers of 2016-2017 and 2022-2023 (Figure 1), when within a few weeks, several high-intensity, rapidly spreading fires caused damage to populations and local ecosystems and claimed dozens of lives.
Faced with these high-impact disasters, it is important to identify the factor(s) that explain how localized fires escalated into megafires. This task was addressed in a study whose results were recently published in the journal Weather and climate extremes yand which we summarize below.
Figure 1. Panel (a) shows in violet the megafire that occurred in central-southern Chile on January 26, 2017, while panel (b) shows the one that occurred in 2023. Both panels highlight the magnitude of the fires and the smoke columns.
Mega-fires and Extreme Weather:
The study revealed unprecedented extreme temperatures across much of south-central Chile during the mega-fires, including the affected areas. For reference, maximum temperatures in Chillán reached 41.5°C on January 26, 2016, and 41.6°C on February 3, 2023, exceeding previous records by nearly 1.5°C. This extreme heat was the primary factor in the exceptionally low humidity during these periods, directly contributing to vegetation and soil desiccation.
In both cases, the intense heat and low humidity at the local level were facilitated by larger-scale meteorological configurations, which also generated the eastern Puelche wind in the foothills, further reinforcing air subsidence and warming. Simultaneously, this meteorological configuration accelerated southerly winds over the coastal mountain range, which were particularly intense and promoted rapid-fire advancement in affected areas. While acknowledging that the mega-fires were human-initiated and occurred in terrain prone to burning due to high fuel loads, their propagation in the summers of 2017 and 2023 appears largely determined by unprecedented extreme weather conditions.
The research also indicates that current weather forecasting systems can predict extreme heat events several days in advance, potentially significantly improving preparation and response to future mega-fires in south-central Chile.
Finally, a formal attribution of these extreme weather events to climate change demonstrated that their intensity and frequency have increased in the region due to greenhouse gas emissions. This increase will continue to manifest in the coming decades if global temperature rises are not curtailed.
Recommendations
- Activate alerts for potential large-scale, high-intensity mega-fires when extreme temperatures above 40°C are forecasted in south-central Chile during summer.
- Implement continuous prevention and mitigation actions against mega-fire effects by governmental institutions, private companies, and the general public within the current climate change scenario.
- Substantially reduce human-caused ignitions (currently approximately 5,000 per season), as each has the potential to develop into a mega-fire. Environmental education and legal prosecution of intentional fire-starters are fundamental to this task. Still, risks of accidental ignitions from infrastructure such as high-voltage power lines and urbanised areas must also be reduced.
- Intervene in vegetation zones dominated by invasive exotic species to ensure heterogeneous vegetation landscapes and reduce fuel loads in risk zones around cities, roads, and other infrastructure. These interventions include the creation and maintenance of firebreaks and the cleaning of urban-rural interface zones. While these activities will not create landscapes immune to forest fires, they will generate conditions less favourable to fire propagation and thus facilitate effective fire control before they transform into mega-fires.
References
Carrasco-Escaff, T., Garreaud, R., Bozkurt, D., Jacques-Coper, M., & Pauchard, A. (2024). The key role of extreme weather and climate change in the occurrence of exceptional fire seasons in south-central Chile. Weather and Climate Extremes, 100716.
Cóbar-Carranza, A. J., García, R. A., Pauchard, A., & Peña, E. (2015). Efecto de la alta temperatura en la germinación y supervivencia de semillas de la especie invasora Pinus contorta y dos especies nativas del sur de Chile. Bosque (Valdivia), 36(1), 53-60.
González, M. E., Lara, A., Urrutia, R., & Bosnich, J. (2011). Cambio climático y su impacto potencial en la ocurrencia de incendios forestales en la zona centro-sur de Chile (33º-42º S). Bosque (Valdivia), 32(3), 215-219.
González, M. E., Gómez‐González, S., Lara, A., Garreaud, R., & Díaz‐Hormazábal, I. (2018). The 2010–2015 Megadrought and its influence on the fire regime in central and south‐central Chile. Ecosphere, 9(8), e02300.
Pauchard, A., García, R. A., Pena, E., González, C., Cavieres, L. A., & Bustamante, R. O. (2008). Positive feedbacks between plant invasions and fire regimes: Teline monspessulana (L.) K. Koch (Fabaceae) in central Chile. Biological Invasions, 10, 547-553.
Pozo, R. A., Galleguillos, M., González, M. E., Vásquez, F., & Arriagada, R. (2022). Assessing the socio-economic and land-cover drivers of wildfire activity and its spatiotemporal distribution in south-central Chile. Science of the total environment, 810, 152002.