Methane fluxes from tropical wetlands of the Orinoco River Basin and their regional implications

Abstract. The Llanos del Orinoco, a vast tropical savanna floodplain in northern South America, plays a significant yet understudied role in the global methane (CH₄) budget. This study synthesizes existing data to evaluate CH₄ emissions from the region, highlighting the interplay between natural processes and anthropogenic influences. Top-down and bottom-up estimates for 2018 reveal annual CH₄ emissions ranging from 3.27 ± 0.71 to 5.31 ± 2.50, with wetlands contributing 41–70 % of total fluxes. Seasonal variability follows precipitation patterns, with greater emissions occurring during the rainy season (April–October). However, discrepancies between global biogeochemical models and sparse field measurements underscore significant uncertainties, exacerbated by inconsistencies in inundation mapping and outdated local data. Anthropogenic activities, including oil extraction, livestock farming, and expanding rice cultivation, further modulate CH₄ fluxes, though their impacts remain poorly quantified. Historical trends show declining precipitation and increasing temperatures, with models predicting more extreme weather events, potentially reducing wetland extent but favouring CH₄ release during remaining inundated periods. Critical research gaps, including the need for updated field measurements, improved inundation mapping, and a better understanding of neglected habitats like peatlands and seasonal wetlands, are discussed. Addressing these gaps is essential for refining global and regional CH₄ budgets and developing mitigation strategies. This work calls for integrated monitoring efforts to reconcile model disparities, assess land-use impacts, and predict responses to climate change, ensuring accurate representation of the Llanos del Orinoco in regional and global carbon cycle models.