Tue, Mar 12, 2019 - Page 9 News List

Climate change is
reshaping Australia’s forests

Scientists said it is getting harder to plan for climate change as droughts, heat waves, bushfires and rising temperatures are driving ecosystems toward collapse

By Graham Readfearn  /  The Guardian

Illustration: Yusha

Australia’s forests are being reshaped by climate change as droughts, heat waves, rising temperatures and bushfires drive ecosystems towards collapse, ecologists said.

Trees are dying, canopies are getting thinner and the rate that plants produce seeds is falling.

Ecologists have long predicted that climate change would have major consequences for Australia’s forests. Now they believe that those effects are unfolding.

“The whole thing is unraveling,” said David Bowman, a professor of environmental change biology at the University of Tasmania who studies the effects of climate change and fire on trees. “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 last year’s State of the Climate 2018 report published by the Commonwealth Scientific and Industrial Research Organisation and the Australian Bureau of Meteorology, large parts of the country have experienced increases in weather patterns favorable to fires.

Rainfall has dropped in the southeast and southwest of the country, temperatures have warmed by an average of 1°C, and a “shift to a warmer climate in Australia is accompanied by more extreme daily heat events,” the report said.

Forests across Australia are changing, Murdoch University ecologist Joe Fontaine said.

“Impacts are direct — trees dying from heat and drought — as well as indirect — more fire, fewer seeds and a raft of associated feedbacks,” Fontaine said.

Leaves are the “machinery that makes the plant work” and how those leaves cope with heat depends on moisture reserves, he said.

“The question then is, how much do you have in reserve?” he said. “A lot of us are really concerned about that.”

Fontaine has studied one large shrub species — the southwestern native Hooker’s banksia — and found that seed production has “halved in the last 30 years,” which was “definitely a climate-driven problem with increased drought,” he said.

Last spring, Fontaine and colleagues inspected an area 300km north of Perth where the banksias had been hit by fire several years earlier. He wanted to know if they could cope with fire on top of the area’s long-term reduction in rainfall.

“At this stage, years after fire, those plants should be recovering and really going for it,” he said. “Except instead these banksias were dead and falling over left and right. The young plants were dying too — this area was losing all their young vigorous plants. With more bushfire, this species is at real risk of being wiped off the map.”

INTERVAL SQUEEZE

A study of the effects of a heat wave in 2010 and 2011 in southwest Australia that followed long-term drops in rainfall found that the large jarrah eucalypts and the area’s giant banksias were severely affected.

A knock-on effect was that the area became even more prone to fires, another study said.

Bowman said that the consequences of the changing climate are “absolutely” happening.

He said that he and his colleagues have found that big eucalypts grow slower as temperatures rise and alpine ash forests are at risk of being wiped out because fires are coming along too often.

That is part of a phenomenon known as the “interval squeeze,” where species that are adapted to cope with drought or fire struggle when the time between impacts gets shorter.

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