Mangrove dieback reveals an unexpected source of methane

ARC-supported researchers from Southern Cross University were some of the first on the scene to investigate the unprecedented dieback of mangrove forests along a 1000 kilometre stretch of coastline in northern Australia’s Gulf of Carpentaria.

The loss of 7,400 hectares of mangrove forest occurred during 2015-2016, and is thought to be the result of a combination of extreme temperatures, drought and lowered sea levels.

Supported by ARC funding, Dr Luke Jeffrey, who was a PhD candidate at the time, and a large multidisciplinary research team led by ARC Discovery Early Career Researcher Award (DECRA) recipient, Associate Professor Damien Maher, headed to the Gulf of Carpentaria to examine the consequences.

The team had an opportunity to compare methane emissions from mangrove tree-stems in living forest with those from the dead mangrove forests, to understand what happens when climatic-change stressors result in forest mortality.

The researchers say the results revealed that while living mangroves emit some methane, dead mangroves emit much more. This discovery has significant implications for greenhouse gas emissions from these valuable coastal habitats. It is also the first time that scientists have been able to quantify emissions from mangrove tree-stems, and adds to our understanding of the role of these ecosystems globally.

“WHAT WAS CONCERNING WAS THAT THE DEAD MANGROVE FOREST EMITTED ABOUT EIGHT TIMES MORE METHANE THAN THE LIVING FOREST,” SAYS DR LUKE JEFFREY.

 

Image: The research team on the way to measuring methane emissions from a forest of dead mangroves in the Gulf of Carpentaria. Credit: Southern Cross University.