Mangrove ecosystems have long been heralded as powerful natural allies in the global effort to mitigate climate change due to their exceptional ability to store carbon. Often described as blue carbon ecosystems, mangroves are known for their dense biomass and the substantial carbon reserves locked deep within their sediments. This carbon sequestration prowess has positioned mangroves at the forefront of climate mitigation strategies worldwide. However, recent research reveals a more nuanced interaction between carbon storage and greenhouse gas emissions that could reshape our understanding of these vital coastal habitats and their role in global carbon budgets.
While the capacity of mangroves to bury carbon in sediments is undisputed, their methane emissions introduce a complex dynamic that may offset some of their net carbon burial benefits. Methane, as a potent greenhouse gas, has a global warming potential many times higher than carbon dioxide over short timescales. Traditionally, attention has been focused on methane released from wetland soils, including those underlying mangrove forests. Yet emerging evidence now suggests that methane might also be transported directly through the stems of mangrove trees themselves, representing a heretofore underappreciated pathway for methane release into the atmosphere.
This novel understanding stems from a groundbreaking global quantification effort that combines direct field measurements, extensive global datasets, and sophisticated machine learning models. The study harnesses the power of interdisciplinary approaches to estimate the scale of stem-mediated methane emissions on a planetary scale. Surprisingly, the analysis reveals that mangrove tree stems emit methane at a magnitude that has previously been unexpected, thus requiring a re-evaluation of their net contribution to greenhouse gas fluxes.
The comprehensive analysis estimates that annual methane emissions through mangrove tree stems amount to approximately 730.60 gigagrams per year, with a 95% confidence interval between 586.09 and 876.93 gigagrams. This volume of methane release is remarkable and calls attention to an offsetting effect on the sediment carbon burial capacity of these ecosystems, which is reduced by roughly 16.9% owing to the methane emitted via stems. When combined with methane released directly from soils, stem emissions further intensify the overall methane budget, ultimately counterbalancing about 27.5% of the total blue carbon sequestration attributed to mangroves.
Exploring the environmental and physiological factors that influence stem methane fluxes, the study identifies several key variables intricately linked to these emissions. Wood density stands out as a pivotal factor, with lower wood density correlating to higher methane release through stems. This finding suggests that the structural characteristics of mangrove trees may play an essential role in gas transport dynamics. Additionally, the concentration of organic carbon in nearby soils influences methane generation and subsequent emission, highlighting the interconnected nature of sediment biogeochemistry and plant physiology.
Salinity emerges as another influential parameter; the research found that lower salinity conditions tend to promote higher methane emissions from mangrove stems. This association may reflect the sensitivity of microbial communities and methane production pathways in sediments to salt concentration gradients. Finally, wood water content correlates positively with methane emissions, reinforcing the idea that water-saturated tissues serve as conduits or reservoirs facilitating methane transport from sediment to atmosphere via mangrove aboveground biomass.
These insights provide crucial evidence supporting the hypothesis that mangrove stems act primarily as conduits for soil-derived methane. This mechanism suggests that methane generated in anoxic sediment layers traverses through the roots and vascular tissues, bypassing conventional soil oxidation processes that typically mitigate methane release. As a result, methane escapes efflux pathways in a more direct manner, amplifying atmospheric emissions despite the presence of an extensive carbon sink in the sediment.
The implications of this discovery are profound for global carbon accounting and climate change mitigation strategies. Incorporating stem-mediated methane fluxes into blue carbon budgets ensures more accurate predictions of the net greenhouse gas balance associated with mangrove ecosystems. By highlighting the considerable methane offset, the study cautions that neglecting this emission component could lead to overestimations of the climate mitigation potential of mangroves.
Moreover, the findings stimulate new avenues for future research and environmental management. Understanding how wood density, salinity, soil organic carbon, and wood water content drive methane emissions empowers scientists and policymakers to develop more nuanced strategies for preserving and restoring mangrove forests. Targeted conservation and restoration efforts might consequently optimize carbon sequestration while minimizing undesired methane fluxes.
The methodology employed in this research represents a significant advancement in the field. Combining diverse data collection from multiple global research sites with machine learning upscaling techniques offers a powerful framework for assessing ecosystem-scale emissions from complex and heterogeneous landscapes. This integrative approach not only refines the global methane budget but also sets a precedent for examining gas exchanges in other wetland ecosystems.
Indeed, the concept of trees acting as methane conduits is gaining traction beyond mangrove forests, paralleling findings in various freshwater wetland environments. Yet, the magnitude and environmental controls elucidated in mangroves underscore the uniqueness of these coastal forests in global methane dynamics. Such revelations necessitate revisiting ecosystem models and integrating tree-mediated pathways when forecasting greenhouse gas fluxes under changing climatic conditions.
Taken together, this study sheds light on an overlooked dimension of mangrove biogeochemistry. While these forests remain critical carbon sinks, the role of tree stem methane emissions must be recognized as an important counterbalance to their carbon burial benefits. This paradigm shift enriches our understanding of blue carbon ecosystems and propels efforts to refine climate mitigation policies grounded in ecological realities.
Ultimately, the discovery described here challenges the simplistic notion of mangroves as carbon storage panaceas by revealing a nuanced interplay between carbon sequestration and methane emission. This knowledge equips scientists and environmental managers with a more holistic perspective on how these vital coastal forests function within Earth’s climate system. Enhanced accounting of such methane pathways will strengthen the scientific basis for integrating nature-based solutions into global climate strategies.
Continued investigation into the mechanisms underlying stem methane emissions, their variability across species and environmental gradients, and their response to anthropogenic disturbances promises to further illuminate the complex role of mangroves. Combining ecophysiology, microbial ecology, and advanced remote sensing methods may yield essential insights for sustaining and harnessing the full climate potential of these blue carbon champions.
As the planet grapples with escalating climate challenges, deepening our understanding of nuances like stem-mediated methane fluxes in mangrove forests exemplifies the need for comprehensive ecosystem science. This research represents a significant stride toward unveiling the intricate carbon and greenhouse gas balances operating in natural systems that form the bedrock of humanity’s climate future.
Subject of Research:
Carbon cycling in mangrove ecosystems, specifically methane emissions from mangrove tree stems and their impact on blue carbon sequestration.
Article Title:
Mangrove sediment carbon burial offset by methane emissions from mangrove tree stems.
Article References:
Qin, G., Lu, Z., Sanders, C. et al. Mangrove sediment carbon burial offset by methane emissions from mangrove tree stems. Nat. Geosci. (2025). https://doi.org/10.1038/s41561-025-01848-4
Image Credits: AI Generated
DOI: https://doi.org/10.1038/s41561-025-01848-4
Keywords:
Mangrove ecosystems, blue carbon, methane emissions, carbon sequestration, tree stem methane flux, sediment organic carbon, salinity, wood density, methane oxidation, greenhouse gases, climate change mitigation, wetland carbon cycling, machine learning upscaling
