Lower methane emissions from coastal ecosystems
They are thin streaks of vegetation where the ocean meets the land, and they are found all over our planet – from the poles to the tropics. But despite their relatively small areas globally, coastal ecosystems are crucial hot spots for carbon storage. New research from the University of Gothenburg now shows that methane emissions from these areas are lower than previously thought.
Seagrass meadows, saltmarshes, and mangrove forests are examples of key areas where ecosystems have been shown to be effective at capturing and storing carbon, thereby mitigating climate change and its impacts.
An unresolved issue is how much of the stored carbon is released back into the atmosphere as carbon dioxide and methane. Previous research has concluded that these so-called “blue carbon” ecosystems emitted large amounts of methane, which partially reduces net climatic benefits of carbon storage.
“My findings challenge the conventional assumptions and reveal that methane emissions from coastal ecosystems are lower than previously estimated and significantly lower than those from freshwater ecosystems such as lakes and reservoirs,” says Yvonne Yu Yan Yau, Doctoral Student at the Department of Marine Sciences, University of Gothenburg.
“Coastal ecosystems have a greater potential to store carbon than we previously thought. They are very important for our climate, and it is urgent that we protect them,” says Yvonne Yu Yan Yau.
Urgent to protect coastal ecosystems
Coastal ecosystems are among the most important, yet they are the most exposed on Earth. They are vulnerable to threats mainly from human activities: coastal development, pollution, and deforestation to make way for crops. But they are also vulnerable to the effects of climate change, such as rising temperatures and ocean acidification.
Yvonne Yu Yan Yau's studies did not just focus on the emissions of the methane. The thesis investigated the underexplored pathways such as groundwater, and detected that high methane is transported through groundwater to mangroves and saltmarshes.
The research also showed that not all the methane produced in these ecosystems was released into the atmosphere. Instead, some of the methane was consumed in the sediment and in the water column, reducing the methane released into the atmosphere. The ability to consume methane is also important to include in order to make accurate calculations for methane budgets.
“Glacier lagoons are also one of the coastal ecosystems I studied, since glaciers also stores a lot of organic carbon. With the melting of glacier, there will be an input of the carbon to the nearby coastal waters. We also detected elevated methane near the glacier,” says Yvonne Yu Yan Yau.
Link to thesis: Methane offsets to carbon sequestration in coastal ecosystems.
Contact: Yvonne Yu Yan Yau, Doctoral Student at the Department of Marine Sciences, University of Gothenburg,
email: yu.yan.yau@gu.se
Writer: Annika Wall
