Murdoch University scientists say parts of our climate change impacted forests may never be the same again.

Hounded in the last decade by increasing frequencies of drought, heatwaves, insect pests, disease and fire, trees are often more dead than alive with their regrowth vulnerable to further climate change-caused impacts, the researchers say.

In a series of papers, the researchers have examined the recovery of the Northern Jarrah Forest in South-West Australia following the drought and heatwaves of 2010-11. Around 16,000 hectares suddenly collapsed after the disturbances.

They found that many of the jarrah and marri trees affected underwent a profound structural change when they began to regrow, from tall open stands, to short, multi-stemmed individuals with large dead trunks standing over the regrowth.

These younger, shorter trees are far more vulnerable to the impacts of climate change, especially increased fire threat because of their thin bark and inability to resprout, the scientists say.

Carbon loss

In the latest published work, the scientists found that the dead trunks represented a significant carbon loss and it was unlikely impacted areas of the forest would regain their carbon storage in the future.

Forests play an integral role in the carbon cycle, absorbing approximately one-third of the carbon dioxide released from burning fossil fuels every year.

Researcher Lewis Walden said the team visited areas of forest from Brookton Highway to Dwellingup five times over the course of two years to document regrowth and measure dead and live pools of carbon, finding encouraging signs of recovery.

“But many of the stands that experienced die off are likely to be burnt by either wild fire or planned burns before they have completely recovered, so it’s unlikely these areas of the Northern Jarrah Forest will regain or increase their carbon storage,” Mr Walden said.

Researcher Dr Joe Fontaine said the Northern Jarrah Forest was fighting back, but it may not get the time it needs to fully recover.

“We want resilient forests for many reasons, not least to continue to mitigate climate change,” he said. “But the next die off caused by heatwaves or fire could make the full recovery of some sections of forest unlikely - research is showing that such disturbances are occurring more frequently in our changing climate.

Unfortunately, there will be no silver bullet to ‘save’ our forests from climate change impacts. But by understanding the complexities of the forest, we can help to inform management practices that helps to retain our south-western forests for future generations.

The latest research was published in the journal Global Change Biology.