Fires Reshaping Southern Amazonian Forests: New Research Highlights Degradation and Carbon Loss

Posted by Ted Feldpausch

7 January 2025

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We recently published a paper led by PhD student Maurivan Barros Pereira (State University of Mato Grosso (UNEMAT)), supervised by Prof. Ted Feldpausch and co-supervised by Drs Ben Hur Marimon Junior and Fernando Elias da Silva. The findings were published in the journal Forest Ecology and Management, “Post-fire changes in tree diversity, composition and carbon in seasonal forests in the southern Amazonia”. The study was conducted in the Amazon-Cerrado transition in the Arc of Deforestation, a critical transition zone between the Amazon rainforest and the Cerrado savanna. This region is increasingly threatened by deforestation and fires, with potentially devastating consequences for biodiversity and carbon storage.

Our study compared unburned forests with areas that had experienced single and multiple fires. We found evidence that fire is significantly altering these ecosystems:

• Shifting Species Composition: Fires are leading to a decline in tree species that thrive in undisturbed forest environments. While the number of species adapted to open areas (Cerrado) or those that can tolerate both forest and open conditions (generalists) remained relatively stable, the overall composition is shifting towards a less diverse and more homogenized forest. This indicates a degradation process rather than a direct conversion to savanna.
• Reduced Carbon Storage: A key finding is the significant reduction in carbon stocks in burned forests. This highlights the crucial role these forests play in carbon sequestration and the negative impact of fires on their ability to mitigate climate change. Multiple fires led to even greater carbon losses.
• Impact on Forest Structure: We also observed a decrease in tree density (the number of trees per hectare) in burned areas, further demonstrating the structural damage caused by fire.

Figure: Floristic gradient associated with fire frequency in seasonal forests in the southern Amazonia. * = indicator tree species of forest classes according to INDVAL.

These findings underscore the urgent need for conservation efforts to protect these fire-affected ecosystems. Increased fire frequency, driven by human activities and exacerbated by climate change, is pushing these forests towards a new, degraded state with reduced biodiversity and diminished capacity to store carbon. Our research emphasises the importance of preventing fires and managing landscapes sustainably to safeguard the future of these unique and valuable forests.

The paper can be access here: https://www.sciencedirect.com/science/article/pii/S037811272400759X