j.g. pausas' blog

During the 2016/17 fire season in Chile, wildfires burned about 600,000 ha, a record for the region. The fact that the region was covered by large and dense tree plantations that created a continuous fuel bed, contributed to these massive wildfires (Fig. 1), together with an intense drought with strong head waves. That is, afforestation as established in Chile can lead to larger and more severe fires under warming conditions [1]. These mega-fires have multiple socioeconomic consequences. A recent analysis suggests that afforestation generates the emission of large amounts of greenhouse gases (they act as a net carbon source) while native forests act as a sink (Figure 2). 

Figure 1: Analysis of the areas affected by fires according to types of use (forest plantations, native forest, Scrubland + pastures, and agricultural areas), in relation to what is available in each of the 4 regions that have burned the most (V, RM, VI, VII are: Valparaiso, Metropolitana, O’Higgins, and Maule). Positive data means that fire has positively selected this type of use (it has burned more than expected by the area it occupies); the negative data indicates that fire tends to avoid such land use. There is a strong tendency for plantations to burn more than expected according to their abundance in the landscape (positive values), while native forests, scrub, or agricultural areas are burned similarly or less than expected according to their abundance (negative values). The region VII (Maule) is the most extreme in the positive selection of plantations and negative of other uses. Elaborated based on official SIDCO-CONAF data (Chile) [2].

Figure 2, left: Forest plantations act as a net carbon source in contrast to the native forests (sink). Shown is the carbon balance (million tons of CO₂-equivalent; including CO₂, CH₄, and N₂O) for the period 1990–2018, including capture (biomass increment and long-lived harvested wood products) and emissions (short-lived harvested wood products and wildfires), for native forests and for plantations in Chile. Dots are mean annual values (the outlier for plantations corresponds to the 2017 mega-fires). From [3]

Figure 2, right: The contribution of tree plantations to burned area is increasing. Shown are the area of plantations burnt annually (ha, in orange) and the proportion of the area of plantations burnt annually in relation to the total area burnt, including native forests, shrublands, and grasslands (%; data in black symbols, fit in red for the period 1984–2022). Note that the proportion of plantations burnt increases more steadily than the area of plantations burnt, probably as an indication that plantations have become increasingly more fire-prone compared with other land uses. From [3]

Reference
[1] Leverkus A.B., Thorn S., Lindenmayer D.B. & Pausas J.G. 2022. Tree planting goals must account for wildfires. Science 376: 588–589. [doi | science | pdf]

[2] Incendios en Chile 2017, jgpausas.blogs.uv.es/2017/02/10

[3] Gómez-González S, Miranda A, Hoyos-Santillan J, Lara A, Moraga P & Pausas J.G. 2024. Afforestation and climate mitigation: lessons from Chile. Trends Ecol. Evol. 39(1) [doi | pdf]

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