In the vast expanse of the Amazon rainforest, productivity is primarily limited by the availability of phosphorus, a critical nutrient required for plant growth. While this nutrient scarcity has long constrained the rainforest’s ability to act as a potent carbon sink, recent research reveals an unexpected source that mitigates this limitation: dust and aerosols transported by atmospheric plumes originating from fires far afield. These plumes, primarily arising from deforestation and savannah fires in the southern arc of deforestation surrounding the Amazon basin, carry nutrient-rich particles that deposit phosphorus across vast distances, thereby augmenting forest productivity in regions previously thought to be isolated from such external nutrient inputs.
The study employed an innovative combination of satellite observations and atmospheric transport modeling to track the trajectories of aerosols originating from intense biomass burning in peripheral regions. By integrating geospatial datasets with advanced feature importance analytical techniques, the researchers were able to quantify the extent to which fire-derived phosphorus deposition influences gross primary productivity (GPP) across the Amazon rainforest. This comprehensive methodology allowed the delineation of a distinct south-to-northeast gradient in phosphorus deposition, a phenomenon intricately aligned with spatial patterns observed in sun-induced fluorescence (SIF) — a reliable proxy for GPP in dense forest canopies.
One of the most fascinating revelations of this research is the magnitude of phosphorus fertilization imparted by these fire-emitted aerosols. Long-term phosphorus deposition emerged as the single strongest predictor of gross primary productivity variability, accounting for an astonishing 22.5% of total spatial variation in forest productivity across the Amazon basin. The correlation was striking: each incremental increase of 1 mg of phosphorus per square meter per year in deposition correlated with gains of approximately 7.4 grams of carbon per square meter per year in forest carbon assimilation. This quantifiable link underscores the importance of atmospheric nutrient fluxes as a critical, yet previously underappreciated, driver of forest carbon dynamics.
By elucidating the role of distant fire emissions in alleviating phosphorus constraints, the study offers new insight into complex nutrient cycling processes that transcend geographical and ecological boundaries. Such nutrient fertilization effects challenge the simplistic view of tropical forests as closed nutrient systems solely dependent on internally recycled nutrients and highlight the interconnectedness of regional fire regimes and forest biogeochemistry. The capacity of these remote fires to provide essential nutrients may partially counterbalance the carbon losses generated by deforestation and biomass burning, effectively blunting some of the deleterious impacts on carbon sequestration potential.
This recognition of long-range nutrient deposition has profound implications for global carbon budget assessments and climate modeling efforts. Traditional models often underestimate forest carbon uptake by ignoring or simplifying nutrient constraints and their modulation by atmospheric inputs. Incorporating these phosphorus deposition gradients and their fertilization effects into ecosystem models will enhance predictive accuracy for carbon fluxes under future land-use and fire scenario projections. Moreover, the findings suggest that as deforestation patterns shift and fire activity evolves under climate change pressures, the biogeochemical feedbacks influencing forest productivity may be both complex and spatially heterogeneous.
Atmospheric transport modeling played a pivotal role in this research by simulating the movement of particulate matter emitted from fire hotspots across the Amazonian periphery. Coupled with satellite data capturing aerosol optical depth and phosphorus concentrations, these models traced how nutrient-rich aerosols travel hundreds to thousands of kilometers from source regions. This enabled the mapping of phosphorus deposition fields showing increased nutrient inputs in the southern and northeastern Amazon regions. The spatial consistency between these deposition patterns and observed SIF data provided compelling cross-validation of model outputs and empirical productivity indicators.
Beyond phosphorus, the study also indirectly highlights the broader importance of fire-derived aerosol deposition in biogeochemical cycles. Fires release a smorgasbord of nutrients and trace elements, some of which may synergistically influence forest nutrition and growth. However, phosphorus—due to its critical role as a limiting nutrient—emerged as the dominant element underpinning enhanced forest productivity in this context. Understanding the suite of nutrients transported by biomass burning aerosols and their ecological impacts could pave the way for refining nutrient cycling paradigms across tropical ecosystems.
The ecological consequences of this nutrient subsidy extend beyond photosynthesis and carbon assimilation. Enhanced phosphorus availability can foster greater biomass accumulation, influence species composition by favoring nutrient-demanding flora, and alter soil microbial communities that mediate nutrient availability. These cascading effects may reshape forest structure and function on decadal timescales. Importantly, the results underscore that nutrient deposition must be contextualized within the broader landscape of increasing anthropogenic disturbance, where these fertilization effects may mask underlying degradation processes.
The findings also raise intriguing conservation and policy questions. While deforestation-associated fires pose undeniable threats to biodiversity and climate regulation, their role in nutrient redistribution introduces a paradox: some negative impacts might be partially offset through enhanced nutrient inputs supporting adjacent intact forests. This does not imply endorsement of burning practices but rather points to complex feedback loops in the Amazon ecosystem that must be carefully navigated in land management strategies. Balancing fire suppression with maintaining ecological nutrient flows will be critical in optimizing forest resilience.
Moreover, the south-to-northeast phosphorus deposition gradient elucidated in this research offers a spatially explicit framework for targeted monitoring and management. Regions receiving elevated phosphorus inputs could be prioritized for protecting their carbon sequestration potential and studying how nutrient dynamics evolve under shifting fire and climate regimes. Integrating these nutrient flux patterns with on-the-ground ecological observations will enable more nuanced understanding of forest health trajectories.
The research team’s use of sun-induced fluorescence as a proxy for gross primary productivity represents a significant advancement in remote sensing applications for tropical ecosystems. SIF measurements capture light re-emitted by chlorophyll during photosynthesis, providing a near real-time indicator of plant carbon uptake across vast forested regions. Combining such remote sensing data with atmospheric modeling and nutrient deposition assessments epitomizes the multidisciplinary approach necessary to unravel complex earth system interactions.
Finally, the study’s conclusions emphasize that nutrient limitation in tropical forests, once considered a static and inherent constraint, is more dynamic and influenced by anthropogenic activities than previously appreciated. The recognition that distant fires contribute phosphorus nutrients challenges classical ecological models and encourages a reevaluation of how nutrient cycles integrate with global biogeochemical and climate processes. As the Amazon faces escalating pressures from deforestation, climate change, and fire regimes, understanding these complex nutrient-carbon feedbacks is vital for forecasting the rainforest’s future role in mitigating climate change.
In summary, the cutting-edge research conducted by Descals, Janssens, and Peñuelas reveals a hidden but critical driver of Amazon rainforest productivity: nutrient deposition from aerosols transported by fire plumes originating far from the forest itself. By alleviating chronic phosphorus limitations, these fire-derived inputs significantly enhance gross primary productivity and partially offset carbon losses from deforestation and biomass burning. This discovery not only deepens our understanding of tropical forest nutrient cycling but also provides essential insights for improving global carbon budget models amid escalating environmental change.
Subject of Research: Influence of fire-derived nutrient deposition on Amazon rainforest productivity and carbon sequestration.
Article Title: Amazon forest nutrient limitation is mitigated by distant fire emissions.
Article References:
Descals, A., Janssens, I.A. & Peñuelas, J. Amazon forest nutrient limitation is mitigated by distant fire emissions. Nat. Geosci. (2026). https://doi.org/10.1038/s41561-025-01899-7
DOI: https://doi.org/10.1038/s41561-025-01899-7
Image Credits: AI Generated
