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Large colonies of chinstrap penguins in Antarctica are a significant natural source of methane, a greenhouse gas whose impact on global warming is greater than that of carbon dioxide (CO₂).
This has been demonstrated for the first time by a study carried out by the Institute of Marine Sciences of Andalusia (ICMAN), a research centre of the Spanish National Research Council (CSIC), in collaboration with the University of Granada.
The research, published (source in Spanish) in the journal 'Climate and Atmospheric Science', estimates that the guano produced by these birds generates around 490,000 tonnes of methane a year. This amount is comparable to emissions from other recognised natural sources, such as all the world's coastal ocean areas.
Until now, most studies on methane emissions have focused on human activities such as the use of fossil fuels, agriculture and waste management, as well as on domesticated animals. However, large concentrations of wildlife can also generate emissions through the accumulation and decomposition of organic matter.
"The guano that builds up in these bird colonies, which can bring together tens of thousands of individuals, creates extraordinarily intense methane emission hotspots that until now had never been measured or quantified in situ," explains Alejandro Román, a researcher at ICMAN-CSIC and lead author of the study, quoted in a press release (source in Spanish).
To obtain these results, the team carried out direct gas measurements in two large penguin colonies on Deception Island, in the South Shetland Islands archipelago. It also used drones equipped with optical sensors to map the surfaces covered in guano and to estimate the size of the populations.
If the calculation is extended to all Antarctic land areas influenced by these birds, emissions could reach millions of tonnes. "They could amount to around 7 million tonnes of methane per year, a figure of the same order of magnitude as global estimates for other major methane sources associated with animal activity, such as termites," says Emma Huertas, principal investigator of the DICHOSO project, together with Antonio Tovar.
The authors believe that this phenomenon should be included in global emissions inventories and underline the need to study how climate change could alter it by affecting both penguin populations and the soil microorganisms that produce methane as the guano breaks down.