Australia’s forests are dying faster than they can recover

TREES across Australia’s forests are dying at increasing rates as the climate warms, according to a major new study led by Western Sydney University.

The research found a continent-wide rise in background tree mortality, defined as tree loss not caused by fire, clearing or logging.

Published in Nature Plants, the study analysed 83 years of data from more than 2,700 forest plots across Australia.

The plots span a range of forest ecosystems, including tropical rainforests, savannas and temperate eucalypt forests.

Researchers found background tree mortality has increased steadily since the 1940s across all forest types.

Over the same period, tree growth has remained the same or slowed, indicating the trend is not part of a natural cycle of renewal.

The study found the rise in tree deaths closely tracks Australia’s warming and drying climate.

Rising temperatures were identified as the dominant driver of increased mortality.

Tree deaths increased most rapidly in hot, dry regions and in dense forests where competition for water and light intensifies stress.

Senior author Distinguished Professor Belinda Medlyn from Western Sydney University’s Hawkesbury Institute for the Environment said the findings pointed to growing pressure on Australia’s forests.

“Australians rely on their forests for a wide range of ecosystem services, from cultural values and recreation to timber for houses. Increasing tree mortality in our unique forests will affect all of these,” Professor Medlyn said.

“A particular worry is that the forests’ ability to store carbon will decline. This has significant implications for Australia’s net carbon balance,” she said.

Professor Medlyn said forests worldwide currently absorb about one-third of human carbon dioxide emissions.

“If mortality continues to rise while growth stagnates, that buffering capacity will erode,” she said.

She said recent evidence from northern Australia showed tropical rainforests shifting from being net absorbers of carbon to net producers.

“This will weaken the planet’s ability to absorb emissions and amplify existing climate feedbacks, further narrowing the window for stabilising the global climate,” she said.

The study found the combined trend of rising mortality and stagnant growth signals a decline in the resilience of Australian forests.

Researchers said adapting forest management could help safeguard forest health but warned that monitoring capacity has declined.

The study found the number of long-term forest monitoring plots has fallen sharply over the past 25 years.

“Our results highlight the critical need for ongoing forest monitoring that is designed to detect long-term trends, in order to guide effective forest management for the future,” Professor Medlyn said.