When it comes to methane emissions, cows tend to wear most of the blame. But what if we told you that trees and wetlands are also significant contributors?
Two Southern Cross University researchers, Dr Luke Jeffrey and Dr Judith Rosentreter, have secured Australian Research Council (ARC) Discovery Early Career Researcher Award (DECRA) grants worth a total of $891,197 to further their studies on methane emissions from vegetation, soils and water, which have already turned up some game-changing findings.
“Dr Jeffrey and Dr Rosentreter have already made significant contributions to their specialised areas of research, which is very impressive given they’re both still early career researchers. I’m excited about the learnings this next phase of their work will deliver, along with the associated global benefits,” said Professor Mary Spongberg, Southern Cross University’s Deputy Vice Chancellor (Research and Academic Capability).
“These grants really are a testament to the amazing research environment we have at Southern Cross University, and to our support of early-career researchers. Both of these researchers undertook their PhDs here, and are now entering this exciting new phase of their careers at Southern Cross University.”
Methane is a potent greenhouse gas about 45 times stronger at warming our planet's atmosphere than carbon dioxide. Most naturally occurring methane is produced within earth's wetlands. Methane is created when organic carbon from vegetation and soils are slowly decomposed by microbes in these saturated environments. Our preliminary data suggests that in wetland forests the below ground methane is transported upwards by the roots and the bark of trees and then outwards through their stems. But while measuring methane gas emissions our team recently discovered that the bark of melaleuca was home to a unique microbial community that make an easy living out of consuming the potent greenhouse gas. So we now know that bark dwelling microbes have the capacity to regulate the methane emissions from trees and therefore may play an important mitigation role in the global methane cycle and in climate change. With this newfound knowledge and data land managers, decision makers and future climate change mitigation strategies can be better advised in ways to maximize carbon sequestration in forests and avoid potential and unwanted methane emissions.
Dr Jeffrey’s previous research, which earned him a Chancellor’s Medal from Southern Cross University and has been recognised in the United Nations Intergovernmental Panel (IPCC) on Climate Change Assessment Report 6, has shown that wetland trees can emit substantial amounts of methane, or ‘treethane’, via their stems or trunks – a process that, until now, has been broadly overlooked.
“While wetland soils store vast amounts of carbon, they also emit methane, a greenhouse gas that is about 45 times more powerful than carbon dioxide when it comes to warming our planet,” said Dr Jeffrey. Wetland trees tend to suck this soil-produced methane up through their roots and then emit it to the atmosphere via their trunks.
"However, our research has also uncovered hungry and abundant ‘methane-eating’ communities of bacteria living within the bark of the common Australian paperbark tree, which consume the methane and convert it to carbon dioxide – a far less potent greenhouse gas. This paradigm shifting discovery changed how we view the role of wetland forests within the global methane cycle.”
Dr Jeffrey’s $457,155 DECRA research will investigate the diversity and metabolic capabilities of microbial communities within tree bark in other Australian forests. While it’s already known that trees are vitally important for sequestering atmospheric carbon, the role played by tree bark-associated microbiome in regulating other climate-active trace gases such as methane, hydrogen and carbon monoxide is not. It’s hoped that Dr Jeffrey’s research may soon be able to tell us that.
In a different but related area of study, Dr Judith Rosentreter’s new research, funded with an ARC DECRA grant worth $434,042, will focus on identifying and quantifying methane oxidation and production processes in mangrove environments, mostly in soils and water. This will generate the first complete picture of the mangrove methane cycle to accurately quantify Australia’s contribution to global coastal mangrove emissions, which in turn will help to improve strategies for natural climate solutions of Australian coastal wetlands.
Dr Rosentreter has a special interest in assessing greenhouse gas fluxes in coastal environments such as estuaries and coastal wetlands on local, regional and global scales, with some of her previous research papers being cited in the United Nations Intergovernmental Panel (IPCC) on Climate Change Assessment Report 6. She was also invited to review a chapter of the Report.
Other earlier research by Dr Rosentreter, which highlighted the importance of considering methane emissions when evaluating the climate benefits of blue carbon, was used to develop The Global Methane Budget.
“Blue carbon refers to carbon burial in coastal ocean ecosystems such as mangroves, seagrass and salt marshes,” she said. “Efficient as they may be, they do produce greenhouse gas emissions, particularly methane, and these need to be accounted for.”
Dr Rosentreter’s previous work has earned her both a Southern Cross University Chancellor’s Medal and a prestigious Yale Hutchinson Fellowship at Yale University in Connecticut, New York, where her research included producing a global paper on uncertainties in global methane sources and sinks.