Climate extremes will boost methane emissions in the Amazon
The potential role of climate change in escalating harmful emissions worldwide has expanded into the Amazon rainforest.
Climate extremes predicted for the Amazon region, such as excessive rain and prolonged drought, could significantly impact the emission and uptake of methane, a potent greenhouse gas.
Methane emissions from Amazon floodplains
For half the year, steady rainfall and rising river levels result in over 800,000 square kilometers of Amazon rainforest’s floodplains being submerged. These swaths of land comprise 20 percent of the total rainforest area.
The submerged organic matter, broken down by microbial communities, increases methane production. Shockingly, Amazon’s floodplains contribute almost a third of methane emissions from global wetlands.
In stark contrast, the forested regions of higher ground, or “upland forests,” operate as methane sinks. They make an invaluable contribution to mitigating greenhouse gas emissions by removing methane from the atmosphere.
Functionality of soil microbial communities
The research, led by experts at the University of São Paulo (USP) in Brazil, is published in the journal Environmental Microbiome.
“Seasonal floodplains in the Amazon basin are important sources of methane (CH4), while upland forests are known for their sink capacity,” explained the study authors.
“Climate change effects, including shifts in rainfall patterns and rising temperatures, may alter the functionality of soil microbial communities, leading to uncertain changes in CH4 cycling dynamics.”
The findings highlight the urgent need for conservation and management plans that account for Amazon methane emissions.
Methane flow in the Amazon
Júlia Brandão Gontijo, the study’s first author, is a postdoctoral researcher at the University of California, Davis.
“Although it’s already been shown that factors such as air temperature and seasonal flooding can influence the composition of microbial communities and hence affect the flow of methane in these environments, what should we expect in the context of climate change and the projected alterations in rainfall and temperature patterns, with more intense extremes?” said Brandão Gontijo.
The research team designed a 30-day experiment to find answers, testing soil samples from two floodplains and an upland forest in two municipalities located in the west of Pará state.
“To investigate the microbial feedback under climate change scenarios, we performed a microcosm experiment,” noted the researchers.
The Amazon’s methane balance
The samples were subjected to extreme temperatures and humidity. The findings revealed that the number of methane-producing microorganisms increased in both floodplains, potentially indicating future methane emission concerns.
Additionally, methane consumption by the upland forest soil plummeted by 70 percent during warm and dry conditions.
On the contrary, methane production surged significantly during periods of heavy rain. Since the soil is not routinely exposed to extreme humidity, the research shed light on its responsiveness to these conditions. This scenario is particularly concerning.
Implications of the study
“Taken together, our data indicate that CH4 cycle dynamics and microbial communities in Amazonian floodplain and upland forest soils may respond differently to climate change effects,” wrote the study authors.
“We also highlight the potential role of CH4 oxidation pathways in mitigating CH4 emissions in Amazonian floodplains.”
The floodplain microbiome could adapt to climate change, while the upland forest microbiome appears sensitive to its effects. This potential disparity could seriously disrupt the balance of greenhouse gas emissions in the Amazon region in the future.
Considering the enormous significance of the Amazon rainforest biome on a global scale, this could pose a severe problem.
Complex interactions in the Amazon
The study also revealed a glimmer of hope – methanotrophic microorganisms. These methane-consuming life forms use methane as an energy source, giving them the potential to offset an increase in methane emissions.
This is just the beginning. The team is planning to conduct field experiments and laboratory trials with these microorganisms to deepen their understanding of methane cycling dynamics.
The experts noted that the findings emphasize the importance of considering both environmental factors when assessing the dynamics of methane in these distinct ecosystems.
This contributes to our understanding of the complex interactions between climate, hydrology, and microbial processes in the Amazon region, concluded the researchers.
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