Search for: All records

Abstract Understanding the resilience of tropical forests to fire is essential for evaluating their dynamics under climate change and increasing land-use pressures. Here, we assess how different fire frequencies and intensities influence tree mortality and carbon dynamics in southeastern Amazonia. Using a replicated randomized block design with 24 plots (40 × 40 m), we applied four treatments: unburned control, one burn in 2016 (B1), two burns in 2013 and 2016 (B2), and two burns with added fuel (B2+) to increase fire intensity. Forest inventories conducted from 2012 to 2024 measured tree mortality, diversity, composition, and aboveground biomass. Fire frequency and intensity significantly increased mortality, particularly among small trees, but impacts on forest structure and productivity were more nuanced. Aboveground biomass declined modestly in burned plots, with the greatest loss in B2+ (13%). Aboveground net primary productivity (ANPP) dropped immediately post-burn, especially in B2 and B2+, and partially recovered by 2022–2024. In contrast, leaf area index (LAI) and litterfall rebounded within a couple of years, suggesting a degree of structural and functional resilience. Species richness and composition remained relatively stable in the years following the first experimental fires, but gradually declined and shifted in B2 and B2+ plots beginning in 2014. These results indicate that the experimental forests’ resilience to low-intensity and infrequent fires can prevent widespread forest collapse, but repeated and intensified burns likely undermine long-term resilience by altering forest structure, composition, and carbon dynamics. With the southeastern Amazon forests projected to burn more often in the coming decades, our results highlight both the vulnerability and recovery potential of these ecosystems. Maintaining ecological integrity and minimizing additional disturbances that influence fuel availability will be critical for sustaining forest functions under future fire regimes. 

Amazon forests are undergoing rapid transformations driven by deforestation, climate change, fire, and other anthropogenic pressures, leading to the hypothesis that they may be nearing a catastrophic tipping point—beyond which ecosystems could shift to a permanently altered state. This review revisits the concept of an Amazon tipping point and assesses the risk of forest collapse from an ecological perspective. We synthesize evidence showing that environmental stressors can drive critical ecosystem transitions, either gradually through incremental loss of resilience or abruptly via synergistic feedbacks. The interplay between climate and land-use change amplifies risks to biodiversity, ecosystem services, and livelihoods. Yet, there is limited evidence for a single, system-wide tipping point. Instead, the Amazon's resilience—although not unlimited—offers meaningful pathways for recovery. The most immediate and effective strategies to support this resilience include slowing forest loss, mitigating climate change, reducing fire activity, curbing defaunation, and restoring degraded ecosystems. Without decisive action to address direct threats, the Amazon system may be pushed beyond safe ecological-climatological operating limits—even in the absence of sharply defined thresholds—due to the scale and persistence of anthropogenic pressures. Preserving the Amazon's ecological integrity and its vital role in regulating the global climate requires urgent, sustained conservation efforts in collaboration with local and Indigenous communities.