The study, published in Nature by M. H. Nunes, H. C. Muller-Landau, E. B. Görgens and colleagues, focuses on aboveground biomass, or AGB—the mass of trunks, branches, bark and leaves held above the soil. AGB is a critical component of the global carbon cycle because carbon absorbed from the atmosphere through photosynthesis is locked into woody tissue for years or decades. When forests grow, they can remove carbon dioxide from the atmosphere; when trees die, burn or decompose, much of that carbon can return. Measuring how AGB varies across climate gradients therefore provides an important clue to how tropical forests may influence future climate–carbon feedbacks.

For years, scientists have reported apparently conflicting relationships between tropical-forest biomass and climate. Some studies have linked greater biomass primarily to rainfall or water availability, while others have emphasized temperature. Still others have found that drought, rather than average climate conditions, is the most important factor. The new research argues that these disagreements may not necessarily reflect irreconcilable scientific results. Instead, they may arise because forests in different regions operate under different environmental constraints, or because studies have used different methods, spatial scales and measurements. By analysing the three largest tropical forest regions within a unified framework, the researchers sought to separate genuine geographical variation from methodological noise.

The analysis shows that temperature becomes increasingly important in drier forests. In forests where water is already limited, a rise in temperature can intensify atmospheric demand for moisture. Warmer air can hold more water vapour, increasing evaporative demand and forcing trees to lose more water through transpiration. If rainfall does not compensate, trees may close their stomata, reducing carbon dioxide uptake and photosynthesis. Prolonged heat and dryness can also increase hydraulic stress, impair growth and raise mortality risk. According to the study, these temperature-related associations are strongest in the Congo Basin, making its forests particularly sensitive to warming compared with the Amazon and Southeast Asia under similar environmental conditions.

The findings also reveal a different vulnerability in Southeast Asia. There, the strongest declines in aboveground biomass are associated with increasing water limitation. This does not mean that Southeast Asian forests are unaffected by heat, but it suggests that drought-related stress is a particularly powerful constraint on their carbon storage. The distinction matters because climate change does not alter temperature and rainfall independently. A forest may experience a modest change in annual precipitation but a major shift in the length or intensity of dry seasons. Such changes can reduce soil moisture, restrict tree growth and increase the probability that vulnerable trees die during drought episodes.

Rather than treating temperature and drought as separate, uniform influences, the researchers found that their effects intensify with aridity and are modified by local environmental conditions. Aridity describes the balance between atmospheric water demand and available precipitation, and it can reveal stress that rainfall totals alone may conceal. Two forests receiving similar annual rainfall may experience very different levels of biological water stress if one is hotter, has a longer dry season or loses water rapidly from shallow soils. The study indicates that climatic anomalies become more consequential as forests move toward drier conditions, highlighting why regional averages can obscure the mechanisms operating on the ground.

Soils and topography further complicate the picture. Soil properties influence how much water and nutrients remain available to trees, while slopes and elevated terrain affect drainage, rooting conditions and exposure to weather. A forest growing on deep, water-holding soil may tolerate a dry period better than one on a shallow or rapidly draining substrate. Topography can also create fine-scale differences in microclimate and disturbance exposure that are invisible in broad climate maps. By incorporating these environmental factors, the study presents tropical-forest biomass as the outcome of interacting pressures rather than a simple response to one dominant variable.

One of the most striking results appears in the tallest forests. In stands exceeding 70 metres, where carbon stocks can be exceptionally high, storms emerge as a strong negative driver of biomass. Lightning strikes and windthrow can kill or damage large trees, opening gaps in the canopy and releasing stored carbon through decomposition. The effect is especially important because tall trees contain a disproportionate share of a forest’s aboveground carbon. A single storm event can therefore produce a biomass loss far larger than its footprint might suggest. This result also demonstrates why climate-based models that omit disturbance may overestimate the stability of carbon-rich tropical forests.

The study’s broad message is both a warning and a guide for the future. There is no single tropical-forest response to climate change: the Congo Basin may be especially exposed to warming, Southeast Asia to increasing water limitation, and the tallest forests to storm damage, while local soils and terrain can amplify or soften these pressures. Spaceborne LiDAR makes it possible to observe forest structure over enormous areas, offering a powerful complement to ground plots and satellite optical imagery. Yet the researchers emphasize that present-day associations should be interpreted within their environmental context rather than treated as universal laws. Reliable projections of tropical carbon storage will require models that combine temperature, drought, aridity, disturbance, soil conditions and topography. As climate extremes become more frequent, understanding these interactions may determine whether the world’s forests continue to buffer atmospheric carbon—or begin to lose that capacity in different ways across different continents.

Subject of Research: Tropical-forest aboveground biomass and its relationships with climate, drought, storms, soils and topography.

Article Title: Heterogeneous climatic controls on tropical-forest biomass

Article References: Nunes, M.H., Muller-Landau, H.C., Görgens, E.B. et al. Heterogeneous climatic controls on tropical-forest biomass. Nature (2026). https://doi.org/10.1038/s41586-026-10880-2

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DOI: https://doi.org/10.1038/s41586-026-10880-2

Keywords: tropical forests, aboveground biomass, climate change, carbon cycle, drought, warming, Congo Basin, Amazon, Southeast Asia, spaceborne LiDAR, storms, aridity, forest carbon, soils, topography

The Amazon rainforest’s aboveground biomass, predominantly composed of trees and other plant life, is a primary reservoir of carbon. When healthy and thriving, these ecosystems sequester vast quantities of carbon dioxide, mitigating global warming. Historically, natural factors such as droughts and fires have occasionally altered the carbon stock. However, the new findings emphasize that anthropogenic factors — including deforestation, selective logging, and land-use change — have accelerated the disruption of carbon storage in ways previously underestimated.

To unravel these complex carbon dynamics, the researchers employed an innovative combination of satellite remote sensing technology and ground-based measurements. Leveraging advancements in optical and radar imaging, they captured detailed, high-resolution data on forest biomass changes. This multifaceted approach enabled precise monitoring of aboveground carbon stocks over the Amazon basin across multiple years, offering unprecedented temporal and spatial granularity.

Their analysis uncovered that the decade spanning 2010 to 2020 witnessed a sharp decline in the rainforest’s carbon uptake capacity. Human activities, especially illegal logging and expansion of agricultural frontiers, have introduced a heightened degree of fragmentation in large forested areas. Fragmented landscapes not only lose carbon-storing potential but also become more vulnerable to external stressors such as drought and fire, thereby amplifying carbon emissions.

Crucially, the study identifies that the rate of aboveground carbon losses due to human intervention far exceeds natural carbon fluxes resulting from climate variability. This shift suggests that human activities are no longer peripheral stressors but central drivers reshaping the Amazon’s carbon budget. Furthermore, the research indicates that net carbon gains previously observed in certain regions have stagnated or reversed, challenging earlier assumptions about the rainforest’s resilience.

One of the technical breakthroughs in this study lies in the integration of synthetic aperture radar (SAR) data with traditional optical satellite imagery. SAR excels at penetrating cloud cover and dense canopy, a persistent challenge in the perpetually humid tropics. This dual-data synergy allowed researchers to continuously monitor biomass changes despite frequent atmospheric obstructions, enhancing the reliability of carbon estimates.

The implications of these findings extend beyond the Amazon basin itself. Given that the Amazon is often referred to as the “lungs of the Earth,” alterations in its carbon dynamics have far-reaching impacts on the global carbon cycle. Reduced carbon sequestration translates into higher atmospheric concentrations of greenhouse gases, potentially accelerating climate change effects worldwide. This feedback loop could exacerbate drought frequency, forest degradation, and biodiversity loss, setting off a cascade of ecological crises.

Another pivotal aspect detailed in the study is the temporal acceleration of human impacts. The last decade has exhibited an alarming trend: deforestation rates, formerly erratic, have become more concentrated and intense, linked with policy shifts and economic pressures in the region. The study underscores the importance of socio-political factors, demonstrating that environmental outcomes are intricately tied to governance and regional development dynamics.

The researchers also stress the limitations of past monitoring efforts that relied heavily on coarse-resolution data and infrequent sampling. Previous estimates may have understated the carbon losses and overestimated forest recovery rates due to inadequate observational tools. This new methodology provides a more nuanced and precise evaluation, paving the way for better-informed conservation strategies and policy interventions.

In light of these revelations, urgent measures are advocated to curb the accelerating anthropogenic pressures. The study calls for enhanced international cooperation to enforce stricter deforestation controls, promote sustainable land management practices, and support indigenous communities who serve as stewards of biodiverse landscapes. The robustness of Amazon carbon dynamics hinges on collective action, combining scientific vigilance with proactive policy frameworks.

Furthermore, the study highlights the potential of emerging technologies such as hyperspectral imaging and machine learning for near-real-time carbon monitoring. These tools promise to revolutionize how environmental agencies and policymakers track ecosystem health and enforce compliance, ensuring that dynamic carbon stock assessments remain updated and spatially accurate.

To contextualize these findings, the authors drew comparisons across multiple biomes within the Amazon, noting that while some regions exhibit persistent carbon depletion, others retain pockets of resilience. Understanding these spatial nuances enables targeted conservation efforts, focusing resources where recovery potential is greatest. This site-specific insight is indispensable for optimizing carbon sequestration strategies in an era of rapid environmental change.

Beyond carbon dynamics, the human impact on the Amazon deepens the crisis of biodiversity loss. As forests degrade, countless species lose habitat, triggering declines in ecosystem services that support human livelihoods and ecological stability. The study’s results underscore the interconnectedness of carbon, biodiversity, and human well-being, providing a comprehensive framework for holistic environmental stewardship.

This paradigm-shifting research adds urgency to global climate dialogues. The intensification of human influence on the Amazon’s carbon budget diminishes the credibility of the forest as a reliable carbon sink. Consequently, international climate models must adjust projections to account for these altered dynamics to formulate realistic emissions targets and mitigation pathways.

In summation, Fendrich, Feng, Wigneron, and colleagues deliver a compelling narrative backed by robust empirical data: human activities have accelerated the alteration of the Amazon rainforest’s carbon storage capacity in the last decade. This intensification of human influence diminishes the forest’s role as a climate stabilizer and signals an inflection point in the region’s ecological trajectory. The study not only advances scientific understanding but also serves as a clarion call for immediate, coordinated global action to preserve one of Earth’s most vital ecosystems.

Intensive monitoring, coupled with policy reform and community engagement, stands as the path forward if humanity hopes to safeguard the Amazon’s carbon reservoir. Failure to act decisively risks not only the loss of carbon sequestration benefits but also the unraveling of intricate ecological networks and the livelihoods intertwined with them. The Amazon’s future—and indeed the future of the global climate—depends on the choices made now.

Subject of Research: Human impact on the carbon dynamics of the Amazon rainforest and its recent intensification.

Article Title: Human influence on Amazon’s aboveground carbon dynamics intensified over the last decade.

Article References:
Fendrich, A., Feng, Y., Wigneron, JP. et al. Human influence on Amazon’s aboveground carbon dynamics intensified over the last decade. Nat Commun 16, 6681 (2025). https://doi.org/10.1038/s41467-025-61856-1

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