Increase in CH4 emissions in Pantanal wetland lagoon due to extreme drought and sediment exposure

The Pantanal is one of the largest and most unique wetlands on the planet, holding significant carbon stocks in its soils, freshwater and saline-alkaline ecosystems. Despite its importance, it faces threats from natural and man-induced fires, inadequate soil management, deforestation, and the impacts of climate change, such as severe drought-heat events, which may increase CH4 emissions. Given the importance of this ecosystem, we investigated methane (CH4) emissions from limnetic zone, sediments, and marginal soils in a drying lagoon in the Pantanal during a drought period unprecedented in over 75 years. The highest emissions occurred during the drying event, primarily when the water column decreased (7.05 mg CH₄ m⁻² day⁻¹) and along the margins (2.98 mg CH₄ m⁻² day⁻¹). This indicates that the lowering of the water column and exposed sediments became a significant source of CH₄ emissions. Our results suggest that these environments can become large CH₄ emitters during drying events, although current CH₄ emission models underestimate their contribution. With the expected increase in drying events in the Pantanal, it is likely that CH₄ emissions will rise in the coming years, exacerbating global warming and intensifying climate change.