New research reveals some rainforest tree species use self-cooling strategies to withstand rising temperatures, but others are more at risk.
The study, published in the journal Global Change Biology, was led by Kali Middleby, a recent PhD graduate from James Cook University and now postdoctoral researcher at the French Institute for Research and Development.
She said tropical rainforests are vital for biodiversity, carbon storage and climate regulation.
"Unfortunately, heatwaves and droughts are pushing many tree species toward their thermal limits and tropical forests may be particularly vulnerable because they evolved with relatively stable thermal environments," said Dr Middleby.
She said understanding how tropical trees have adapted to temperature is crucial for evaluating their resilience to global warming and helping develop effective management strategies.
From October 2021 to May 2022, scientists sampled trees from 16 forest sites across the Wet Tropics of Queensland. The team measured leaf characteristics that determine how hot leaves get, along with heat tolerance thresholds to assess how at risk the trees were to climate change.
They then used a combination of genetic sequencing and common garden experiments to see if adaptation to climate had influenced their ability to avoid damaging temperatures.
"Two of the three studied species - Darlingia darlingiana (silky oak) and Elaeocarpus grandis (blue fig) - showed a clear ability to reduce the temperature difference between their leaves and the surrounding air, effectively 'self-cooling' in hotter environments," said Dr Middleby.
But she said Cardwellia sublimis (bull oak) lacked this capacity, making it more vulnerable as temperatures rise.
"Leaves on trees with stronger self-cooling strategies stayed farther below damaging temperature thresholds even as air temperatures climbed," said Dr Middleby.
"These species all adapted to their local climates over time, but those adaptations don't necessarily protect them from today's rapid warming.
"To survive future conditions, some species may also need to adjust in real time - through acclimation - but we still don't know which species have that capacity."
She said as heatwaves become more frequent and intense, trees that can't adjust their leaf temperatures may face higher risks of tissue damage, reduced growth or even local extinction.
Link to paper here.
