A new study reveals tree mortality rates are rising across Australia’s diverse ecosystems, driven by warming temperatures and threatening forests’ carbon storage capacity.
BANGKOK: Australia’s forests are losing trees at an accelerating rate as the climate warms, according to a new study published on Tuesday.
The research, which examined decades of data, warns the trend is likely a “widespread phenomenon” beyond Australia.
It analysed forest inventory data from 2,700 plots across the country, ranging from cool moist forests to dry savanna.
Areas affected by logging, clearance or fires were excluded to examine changes in “background tree mortality”.
“What we found is that the mortality rate has consistently increased over time, in all of the different forest types,” said Belinda Medlyn, a professor at Western Sydney University’s Hawkesbury Institute for the Environment.
She told AFP the increase is “very likely caused by the increase in temperature”.
The world has warmed by an average of nearly 1.2 degrees Celsius since the pre-industrial era, with most warming occurring in the last 50 years.
The study, published in the Nature Plants journal, also accounted for forest density by examining stand basal area.
“The (mortality) trend over time remains even after we correct for basal area,” explained Medlyn, who led the research.
The sharpest rise in mortality was observed in tropical savannas, where the number of trees dying increased by 3.2% per year.
Average annual deaths there nearly doubled from close to 15 per 1,000 trees in 1996 to nearly double that number by 2017.
The research found tree deaths are not being matched by new growth, leading to an overall decline in forest stock.
This makes it “very likely that the overall carbon storage capacity in the forests is declining over time”, said Medlyn.
The trend was observed across four ecosystems: tropical savanna, cool temperate forest, warm temperate forest and tropical rainforest.
Medlyn added this suggests it is likely “a widespread phenomenon, not just an Australian thing”.
The rising mortality rate tracks warming and drying linked to climate change, with the fastest rise in hotter, dryer regions.
The findings follow a recent study showing Australia’s tropical rainforests are among the first globally to emit more CO2 than they absorb.
“Forests globally currently sequester about one-third of anthropogenic carbon dioxide emissions,” said Medlyn.
“Our study suggests their capacity to act as buffer will decline over time.”
