Fire is an element that has always been present in Mediterranean ecosystems. Thus, once the direct impacts caused by fires have been overcome, to a greater or lesser extent, in the medium or long term, there is a recovery of forest mass, and life re-emerges.
To what extent does this regeneration occur? How long does it take? What effects does it have on the structure and composition of the vegetation? Answering these questions was the aim of a new study carried out by the Forestry Engineering Department at the University of Cordoba, in which the post-fire dynamics of vegetation in an area of the Sierra Morena mountain rage were analyzed in order to better understand the resilience of ecosystems in the face of different fire recurrence and severity scenarios.
According to the study's principal investigator, Macarena Ortega, the work focused on a non-reforested area affected by two overlapping forest fires in the last 30 years. In this way, through photographic interpretations and field inventories, areas that have burned twice (in 1988 and 2016), areas in which fire has struck only once, and, finally, areas not affected by fires (reference or control areas) were analyzed. Looking at the past of these events, analyzing their evolution over time, and making comparisons between all these scenarios is precisely what allowed the research team to draw conclusions about how vegetation recovers over time.
A scientific basis for prescribed burns
One of the study's main conclusions is that recurrent fires of moderate severity reduce the brush that grows under trees without compromising their regeneration. In the words of another of the researchers who participated in the study, Juan Ramón Molina, "this is further evidence of the utility of prescribed burns, which are, ultimately, moderate-intensity fires, as a scrub management strategy to restore ecosystems and prevent forest disasters." In fact, according to the study, those areas featuring dense woodland and undergrowth and that have only suffered moderate-intensity fires, exhibit full recoveries after 30 years (compared to the control area), almost as if the fire had never occurred.
When woods become overgrown with brush
According to the results of the study, the real problem for woodlands arises when fires occur on a severe and recurrent basis. This was the case in Pino Piñonero, in the area studied; exhibiting recovery after the first fire, the regeneration of the area’s trees was completely thwarted when a second fire struck, as, after severe and recurrent fires woodlands tend to give way to systems in which brush almost completely prevails.
"It would be foolish to plan post-fire restoration without understanding how the ecosystem evolves naturally," adds researcher Macarena Ortega. In this way, the work could serve as a guide to forest restoration strategies and their risks.
The study was carried out by the UCO's Forest Fire Laboratory (LABIF) and the academic institution's Forest Engineering Department, in collaboration with researcher Larissa Yocom, attached to the Forest Resources Department at Utah State University (USA).
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Reference:
Macarena Ortega, Ángel Lora, Larissa Yocom, Rafael Zumaquero, Juan Ramón Molina. Effects of fire recurrence and severity on Mediterranean vegetation dynamics: Implications for structure and composition in southern Spain. Science of the Total Environment, Volume 961, 2025,178392, ISSN 0048-9697, https://doi.org/10.1016/j.scitotenv.2025.178392