Once again, we are hearing that Australia’s forests are being ‘reshaped’ by climate change as droughts, heat waves, rising temperatures and bushfires drive ecosystems towards collapse.

Ecologists have long predicted that climate change would have major consequences for Australia’s forests. Now they believe those impacts are already unfolding. Mountain Journal has often reported on this, for instance:

  • In Tasmania, research has confirmed the trend towards more extreme fire seasons. It suggests that we reached a ‘tipping point’ sometime around the year 2000 and that, since then, there has been an increase in the number of lightning-caused fires and an increase in the average size of the fires. This is impacting on fire sensitive vegetation like the high elevation Pencil Pine (Athrotaxis cupressoides) forests and cool temperate rainforest.
  • Fires have decimated some populations of Alpine Ash and Snow Gum
  • Mountain Ash forests could collapse as a result of climate change

A new report, covered in The Guardian describes one of the processes driving the change, called the ‘interval squeeze’.

We all know that Australia has a climate that is often characterised by extreme weather, Dorothea MacKellar’s land of ‘droughts and flooding rains’. But climate change is increasing the extremes of heat, drought and flood. This means that many species that are adapted to cope with drought or fire struggle when the time between impacts gets shorter.

Prof David Bowman, who studies the impacts of climate change and fire on trees at the University of Tasmania, says the idea that Australia’s forests are well adapted to the country’s variable climate and can withstand fire and drought, was incorrect. “A big misapprehension is that these things are climatologically flexible, but they’re just not,” he says, explaining that Australia’s dominant eucalypts have “fine-tuned their life history around assumptions of fire frequency”, but “climate change is just blowing that up”.

“All this is non-linear,” he says. “What will happen is the system will crash faster than we realise. Yes, it will reassemble and there will be forests, but they won’t look anything like what we have now. We are going to see this transformation before our eyes.”

“The whole thing is unravelling,” says Prof David Bowman. “Most people have no idea that it’s even happening. The system is trying to tell you that if you don’t pay attention then the whole thing will implode. We have to get a grip on climate change.”

According to the 2018 State of the Climate Report, produced by CSIRO and the Bureau of Meteorology, large parts of the country are experiencing increases in weather patterns favourable to fires. The report found that rainfall has dropped in the south-east and south-west of the country, temperatures have warmed by an average of 1C, and a “shift to a warmer climate in Australia is accompanied by more extreme daily heat events”.

Dr Joe Fontaine, an ecologist at Murdoch University, says forests across Australia are changing. “Impacts are direct – trees dying from heat and drought – as well as indirect – more fire, fewer seeds and a raft of associated feedbacks.”

Fontaine says leaves are the “machinery that makes the plant work” and how those leaves cope with heat depends on moisture reserves. “The question then is, how much do you have in reserve? A lot of us are really concerned about that.”