- Claudia Leal Medina, PhD student, University of Freiburg, Germany; Graduate School, Faculty of Forest Sciences and Natural Resources, Austral University of Chile, Valdivia, Chile.
- Mauro E. González, Professor at the Faculty of Forest Sciences and Natural Resources, Austral University of Chile, and Researcher at the Center for Climate and Resilience Research CR2
- Mauricio Galleguillos, Professor at the Faculty of Engineering and Sciences, Adolfo Ibáñez University, and CR2 Researcher
- Javier Lopatín, Professor at the Faculty of Engineering and Sciences, Adolfo Ibáñez University, and CR2 Researcher
- Rocío Urrutia-Jalabert, Researcher, Department of Forest Sciences, University of La Frontera, and CR2 Researcher
Edited by: José Barraza, Science Communicator, CR2
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Radiata pine (Pinus radiata) is a pioneer species naturally adapted to high-severity wildfires, giving it a competitive advantage for colonization and rapid post-fire growth.
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Five years after the 2017 megafire, this exotic species massively invaded high- and medium-severity burned areas in the coastal Maulino forest, reaching average densities of over 9,000 individuals per hectare.
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The invasion of radiata pine significantly alters the dynamics of this forest, generating an alternative successional state where native species, such as the ruil (Nothofagus alessandrii), are displaced. This could accelerate the extinction process of this species and lead to ecosystem collapse.
The loss of biodiversity and ecosystem degradation is a global issue occurring on a large scale, with potentially irreversible consequences for life on our planet. Forests are considered essential, as they cover nearly one-third of the Earth’s land surface (31%) and harbor a large portion of global biodiversity. However, despite efforts in recent decades, forest area continues to decline due to deforestation and degradation worldwide (FAO, 2022).
The south-central zone of Chile is a biodiversity hotspot with a high presence of endemic species, whose habitats are highly threatened, mainly due to land-use change (Echeverría et al., 2006; Aguayo et al., 2009; Zamorano-Elgueta et al., 2015; Miranda et al., 2017; Lara et al., 2023). In this part of the country, particularly in the Coastal Range of the Maule Region, the Maulino coastal forest is one of the ecosystems in Chile that has experienced the greatest loss of area and degradation (Bustamante et al., 2005; Arnold et al., 2009). Only small and scattered remnants of young forests remain, embedded within a forested landscape dominated by radiata pine (Pinus radiata) plantations. These remnant forests are dominated by hualo (Nothofagus glauca) and ruil (Nothofagus alessandrii), species classified as Vulnerable (VU) and Endangered (EN), respectively (Alaniz et al., 2016; Barstow et al., 2017).
Fire has been a prevalent disturbance shaping the structure and composition of Maulino coastal forests (González et al., 2022; San Martín et al., 2022). However, large-scale wildfires (megafires), such as those that occurred during the summer of 2017 under extreme climatic conditions like drought and heatwaves (González et al., 2020), have raised major concerns regarding the resilience of these forests (Pausas, 2012).
Notofagus alessandrii forests have undergone a historical population decline, experiencing a deforestation rate of 8.15% between 1981 and 1991, resulting in the loss of more than 50% of these forests due to replacement by Pinus radiata plantations (Bustamante & Castor, 1998; Grez et al., 1998). In 2017, much of this ecosystem was affected by the “Las Máquinas” wildfire, which burned 34% of the native coastal forests in the Maule Region, impacting nine out of the fifteen remaining populations of N. alessandrii. Of the 314 hectares (ha) of existing forest of this species, 172 ha (55%) were affected (Valencia et al., 2018; Santelices et al., 2022; González et al., 2020), seriously worsening its endangered status (González et al., 2022).
This CR2 policy brief highlights the alarming condition of native forests in the Maule Region following the 2017 megafires, where the invasion of P. radiata dramatically threatens the recovery of N. alessandrii and N. glauca forests—both endemic native species of Chile.
Post-Fire Vegetation Cover Changes in N. alessandrii Remnant Forests
Using high-resolution PlanetScope satellite imagery, a rapid recovery in vegetation cover and vigor was observed in three remnant stands of N. alessandrii five years after the wildfire. Vegetation vigor, represented by the Normalized Difference Vegetation Index (NDVI), showed values consistent with dense vegetation exhibiting high photosynthetic activity.
In the early years after the megafire, NDVI trends varied among the stands depending on fire severity, but by the end of the five-year period, sites with moderate and high severity reached similar vigor levels to those affected by low severity, in line with other studies conducted at the regional scale (Leal-Medina et al., 2024).
Additionally, significant seasonal changes in vegetation vigor were detected. In summer, an increase in vigor was observed two years after the fire in sites affected by high and medium severity, highlighting the effective regrowth of typical deciduous vegetation in these forests. In contrast, during winter—when deciduous vegetation loses its foliage—high and medium severity sites showed high NDVI values in the first post-fire year, which may indicate early establishment of vegetation immediately after the fire. However, this elevated vigor condition does not remain stable in subsequent winter seasons.
Changes in the Composition and Structure of N. alessandrii Forests After the Fire
Field data showed a significant shift in vegetation composition and structure following the fire, linked to the recovery process of Nothofagus alessandrii and the invasion of Pinus radiata.
a. Invasion of Pinus radiata
Analyses revealed a direct relationship between fire severity and the degree of invasion by P. radiata. In high-severity sites, the average density of this species reached 9,760 individuals per hectare five years after the fire (Table 1, Figure 1). This pattern suggests that the original vegetation has undergone drastic changes in composition and structure, due both to canopy tree mortality and the high density of the invasive species. As a result, the ecosystem’s natural recovery process is being severely impacted due to intense competition for critical resources in the early stages of forest development.


b. Post-fire Regeneration of N. alessandrii
Five years after the fires, N. alessandrii reestablished through both vegetative regeneration and seed-based reproduction (Figure 2). Adult individuals in severely affected areas were able to sprout from the base of the trunk (Figure 3), and some surviving adult trees produced seeds that successfully germinated, demonstrating the ruil tree’s resilience and adaptive capacity to fire.

Seventy percent of N. alessandrii trees in areas affected by medium and high severity fires showed vegetative reproduction. This trait has allowed the species to recover from severe fire damage and other anthropogenic disturbances.

On the other hand, seed-based regeneration was only recorded in sites with low and medium severity. This mechanism is crucial for dispersal and genetic diversity in new plant generations and is therefore key for the conservation and adaptive capacity of these endangered populations (San Martín, 2022; Santelices et al., 2023). While N. alessandrii seedlings were recorded, their successful establishment is likely to be limited or threatened by the high density of Pinus radiata, due to intense competition for resources such as light, water, and nutrients during the forest’s early development stages (San Martín, 2022).
A critical factor for successful seed regeneration is the presence of seed-producing adult trees, which were only recorded in sites with low and medium fire severity. In high-severity sites, the fire caused the death of most adult trees, and therefore, it is presumed that there was limited seed availability within the severely burned stands (González et al., 2022).
Recommendations
The invasion of Pinus radiata in Nothofagus alessandrii forests reduces the resilience of these native ecosystems, degrading them irreversibly. The dominance of this exotic species significantly alters forest dynamics, creating an alternative successional state in which native species are displaced by non-native ones. This alteration in forest structure and composition may lead to the extinction of N. alessandrii and the overall collapse of the Maulino forest ecosystem. Therefore, the main recommendations are:
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Monitoring and Control of Invasive Species
Implement monitoring and control programs for Pinus radiata in fire-affected areas, prioritizing highly threatened ecosystems such as Maulino forests dominated by N. alessandrii and N. glauca. It is essential to establish an early detection system for biological invasions in burned areas, using satellite monitoring or field surveys that can quantify early invasions. Additionally, regulations must be strengthened to ensure shared responsibility among forestry companies in preventing and controlling the spread of invasive species in Maulino forests and other ecologically valuable ecosystems. -
Ecological Restoration
Design and implement ecological restoration plans that include invasive species control and reforestation or enrichment with native species under conservation status, such as ruil (N. alessandrii) and hualo (N. glauca). Building partnerships between public agencies, forestry companies, local communities, and non-governmental organizations (NGOs) is key to deploying effective landscape-scale restoration strategies. -
Community Participation and Environmental Education
Promote the involvement of local communities in restoration programs and provide training on identifying conservation-status species and controlling invasive species. This is essential for encouraging the conservation of ruil forests. Furthermore, fostering sustainable economic initiatives based on the conservation of the Maulino forest, such as ecotourism, could enhance the protection and conservation of this endangered species.
References
Aguayo, M., Pauchard, A., Azócar, G., & Parra, O. (2009). Cambio del uso del suelo en el centro sur de Chile a fines del siglo XX: Entendiendo la dinámica espacial y temporal del paisaje. Revista chilena de historia natural, 82(3), 361-374. https://www.scielo.cl/pdf/rchnat/v82n3/art04.pdf
Alaniz, A. J., Galleguillos, M., & Perez-Quezada, J. F. (2016). Assessment of quality of input data used to classify ecosystems according to the IUCN Red List methodology: The case of the central Chile hotspot. Biological Conservation, 204, 378-385. https://doi.org/10.1016/j.biocon.2016.10.038
Arnold, F., Sepúlveda, C., Martín, J., Boshier, D., Penailillo, P., Lander, T., Garrido, P., Harris, S., & Hawthorne, W. (2009). Propuesta de una estrategia de conservacion para los bosques nativos de la subregion costera del Maule. https://doi.org/10.13140/2.1.4928.4802
Barstow, M., Echeverría, C., Baldwin, H., & Rivers, M. C. (2017). Nothofagus alessandrii. The IUCN Red List of Threatened Species 2017: E. T32033A2808995.
Bustamante, R. O., & Castor, C. (1998). The decline of an endangered temperate ecosystem: The ruil (Nothofagus alessandrii) forest in central Chile. Biodiversity & Conservation, 7(12), 1607-1626. https://doi.org/10.1023/A:1008856912888
Bustamante, R. O., Simonetti, J. A., Grez, A. A., & San Martin, J. 2005. Fragmentación y dinámica de regeneración del bosque maulino: Diagnóstico actual y perspectivas futuras. Historia, biodiversidad y ecología de los bosques costeros de Chile, 555-564.
Echeverría, C., Coomes, D., Salas, J., Rey-Benayas, J. M., Lara, A., & Newton, A. (2006). Rapid deforestation and fragmentation of Chilean Temperate Forests. Biological Conservation, 130(4), 481-494. https://doi.org/10.1016/j.biocon.2006.01.017
Organización de las Naciones Unidas para la Agricultura y la Alimentación (FAO). (2022). El estado de los bosques del mundo 2022: Vías forestales hacia la recuperación verde y la creación de economías inclusivas, resilientes y sostenibles. FAO. https://doi.org/10.4060/cb9360es
González, M. E., Galleguillos, M., Lopatin, J., Leal, C., Becerra-Rodas, C., Lara, A., & Martín, J. S. (2022). Surviving in a hostile landscape: Nothofagus alessandrii remnant forests threatened by mega-fires and exotic pine invasion in the coastal range of central Chile. Oryx, 57(2), 228-238. https://doi.org/10.1017/S0030605322000102
González, M.E., Sapiains, R., Gómez-González, S., Garreaud, R., Miranda, A., Galleguillos, M., Jacques, M., Pauchard, A., Hoyos, J., Cordero, L., Vásquez, F., Lara, A., Aldunce, P., Delgado, V., Arriagada, Ugarte, A.M., Sepúlveda, A., Farías, L., García, R., Rondanelli, R.J., Ponce, R.,Vargas, F., Rojas, M., Boisier, J.P., C., Carrasco, Little, C., Osses, M., Zamorano, C., Díaz-Hormazábal, I., Ceballos, A., Guerra, E., Moncada, M., Castillo, I. (2020). Incendios forestales en Chile: causas, impactos y resiliencia. Centro de Ciencia del Clima y la Resiliencia (CR)2, (ANID/FONDAP/15110009), 84 pp. Disponible en https://www.cr2.cl/incendios/