SYDNEY, Aug. 21 (Xinhua) — New research reveals that heat-stressed mountain ash forests in the Australian state of Victoria are rapidly thinning and turning from carbon sinks to carbon sources.
These forests, storing more carbon per hectare than the Amazon, are predicted to lose a quarter of their trees by 2080 due to global warming, according to a statement released Thursday by Australia’s University of Melbourne (UoM).
Native to southeastern Australia and among the world’s tallest trees, mountain ash faces climate-driven stress that will reduce its capacity as a carbon reservoir, warn researchers from UoM and the University of New Hampshire in the United States.
Scientists analyzed almost 50 years of Australian forest data, finding that for every degree of warming, these forests lose around 9 percent of their trees, said the study’s lead researcher Raphael Trouve from UoM.
“A growing tree needs space and resources to survive. Under resource-limited conditions, such as water stress, a big tree will outcompete smaller, surrounding trees, causing their deaths,” Trouve said.
The forests’ natural thinning, driven by competition for water and resources, could significantly reduce the forests’ capacity to store carbon and slow global warming, said the study published in Nature Communications.
“Australia’s mountain ash forests are one of the Earth’s most carbon-dense ecosystems, but our study reveals how climate warming could turn them from carbon sinks into carbon emitters,” Trouve said.
He warned that tree deaths and decomposition will boost carbon emissions equivalent to a million cars driving 10,000 km annually for 75 years, excluding the added threat of increasing bushfires.
The thinning in forests also poses risks to regional water supplies, including Melbourne’s, through altered streamflow and water yield, he added. ■