Karri forests, native plants face extinction, climate experts say


A third of the State’s plant species face extinction and South-West karri forests could be reduced to small pockets even if international climate change targets are met, experts have warned
University of WA school of earth and geographical sciences researcher Ray Wills said the Intergovernmental Panel on Climate Change had recommended a 60 per cent reduction in greenhouse emissions in the hope that global warming could be limited to just 2C, but many SW species would not survive even that rise.
“The majority of species on the planet live in less than a three-degree temperature band so if we increase the temperature by three degrees we put all those species at risk,” he said.
“Eucalypts and close to two-thirds of vegetation and species in the SW live in a close to two-degree temperature band. In the recent history of the planet we’ve never warmed above the temperatures we’re at now during the past 40 to 50 million years and most of the species on the planet have evolved in the past 25 million years in the kind of temperatures we live in or lower, but not higher.”
National Climate Centre figures show the annual mean temperature for WA has increased by a little more than 0.8C since 1910.
Species of banksia, which Dr Wills called the “canary in the coalmine” have already begun dying on a large scale in the Mid-West. “With two degrees of warming my view is for the most part there probably won’t be any banksias left in the wild,” he said.
“They live in a rainfall zone between 500mm and 900mm and if it falls below that we lose them and it will affect eucalypts which grow in that band as well. Certainly up to 3000 species could be at risk with a twodegree temperature increase and we’re talking about any species with less than a 300km range — which is most of the species we know in WA.”
Murdoch University boundarylayer climatologist Tom Lyons said all the climate models predicted that rainfall in the SW also would decrease markedly — by up to 60 per cent over the next 40 to 50 years.
Average rainfall in the SW has fallen about 10 per cent since 1970, which coincides with a global change in atmospheric circulation. Professor Lyons’ research also has shown that widespread clearing has affected rainfall because rain-bearing clouds are more likely to form over native vegetation than cleared paddocks.
The scientists said the combination of rainfall and temperature changes meant even the biggest and most robust species, such as karri, would face survival challenges.
Dr Wills said if the climate forecast was correct, karri forests in Pemberton and Walpole would eventually become marginal remnant stands and already remnant stands would die.
Department of Environment and Conservation principle research scientist Lachie McCaw said karri required up to 1000mm of rain a year. Sustained dry warm weather would result in its distribution shrinking to the wettest and most sheltered areas.


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