Tree planting provides wood, biomass and climate benefits, but the location where those new forests are established matters. An international study by researchers in Spain, Chile and Finland shows that converting non-forested land into planted forests can increase wildfire activity, with contrasting outcomes across temperate regions.
The study, published in the Proceedings of the National Academy of Sciences (PNAS), used satellite records from 2001–2023 to analyse 67,248 patches converted into planted forests. After accounting for climate, accessibility and patch size, afforestation was associated with an average 26% increase in fire occurrence per hectare per year and a 23% increase in expected burned area when fires occurred.
“Forest plantations change the fuel conditions in which fires start and spread. We wanted to understand how these changes differ across landscapes, rather than assuming that tree planting has the same consequences everywhere,” says lead author Irene Repeto-Deudero from the University of Cádiz and the University of Eastern Finland.
The researchers emphasise that wildfires can also undermine the long-term carbon storage expected from tree planting.
“These results therefore require that tree planting initiatives consider their exposure to fire. As the climate warms, increased wildfire risk may impact the capacity of forest plantations to store carbon in the long term,” says the study’s coordinator, Professor Susana Gómez-González of the University of Cádiz.
The findings have practical implications for forestry and land-use planning, particularly where plantation expansion coincides with increasingly severe fire weather.
“Plantations are necessary in many cases to produce wood and other ecosystem services, including soil protection. However, their location must be carefully planned to avoid unintended consequences on local fire regimes,” says Professor Blas Mola-Yudego of the University of Eastern Finland. “Fire risk needs to be considered from the outset, alongside production goals and environmental benefits.”
The strongest increases were found in temperate conifer forest regions, where fire occurrence rose almost threefold and expected burned area approximately doubled. Both measures also increased in Mediterranean regions. However, in temperate broadleaf and mixed forest regions, fires became less frequent but burned larger areas. Temperate grasslands, savannas and shrublands showed reduced fire occurrence without a significant increase in burned area.
“These contrasting responses show why local ecological conditions must guide afforestation decisions. The same intervention can have very different consequences depending on the vegetation, climate and existing fire regime,” says co-author Alejandro Miranda of the University of La Frontera, Chile.
The research involved institutions in Spain, Chile and Finland and received funding from the Spanish Ministerio de Ciencia e Innovación, the Chilean Centre for Climate and Resilience Science (CR2), and the Fondo Nacional de Desarrollo Científico y Tecnológico (FONDECYT), and the European Union’s Horizon Europe project Eco2Adapt (Ecosystem-based Adaptation and Changemaking to Shape, Protect and Maintain the Resilience of Tomorrow’s Forests).
For further information, please contact:
Dr. Irene Repeto-Deudero, [email protected]
Professor Blas Mola-Yudego, [email protected]
Research article:
Repeto-Deudero, I., Miranda, A., Pausas, J. G., Hormazábal, C., Mola-Yudego, B., Lopatin, J., & Gómez-González, S. (2026). Afforestation reshapes wildfire activity across global temperate biomes. Proceedings of the National Academy of Sciences, 123, e2623623123. https://doi.org/10.1073/pnas.2623623123
