Extreme weather events are causing severe damage to native flora and fauna, but the casualties are slipping under the radar
— Some headed for the beach while others took refuge in air-conditioned buildings to escape Australia’s unprecedented weeks-long heatwave this summer.
But for ecosystems up and down the country – languishing far from the cities and the social media glare – there was no escape.
Australia’s Bureau of Meteorology confirmed 2018 was the hottest December since records began in 1910, while January was the hottest month ever recorded.
Climate change has altered Australia’s weather patterns. The BoM and CSIRO say the country has warmed by more than 1°C since 1910, and temperatures will continue to rise.
There have been obvious signs: bushfires, drought and coral bleaching on the Great Barrier Reef. But there have also been less headline-grabbing climate change-related tragedies. Based on studies of past extreme heat events, the affect of this summer’s heatwaves on Australia’s flora and fauna would have been severe, fundamental and, in some cases, deadly.
“I think in a lot of places it would have been carnage,” says James Cook University ecologist Prof Bill Laurance of the January heatwave. “We have just had records after records being broken. We only tend to notice when things start dropping out of the trees. We know that basically, lots of things are dying.”
Prof Ary Hoffmann, a biologist at the University of Melbourne, has studied the impact of climate change on natural systems for more than two decades.
“You are going to get some major ecosystem changes,” he says, “but it’s the interactions that drive things. Our extremes are getting much greater, and so the consequences are going to be greater.”
One study found: “Summer heatwaves and winter warm spells will increase in frequency, duration and amplitude across Australia.” Increases in extreme heat conditions and shifting rainfall patterns have already been seen across the continent.
“We know that in heatwaves animals have a temperature threshold and above that, they start to die” — Prof Bill Laurance
One 2018 study, led by Hoffmann, pulled together eight case studies showing how aspects of climate change such as drought, extreme heat and changes to rainfall were working together to devastate ecosystems.
Pest outbreaks – themselves likely promoted by climate change – were harming trees already struggling though persistent droughts and heatwaves. Intervals between bushfires were not long enough to allow seeds to germinate and “drastic management interventions” were required to keep alpine ash ecosystems viable. Birds and mammals in the wet tropics were moving up mountains to stay in their preferred temperature ranges.
According to Laurance, the damage caused by climate change is mostly out of sight of field biologists, and major problems caused by heatwaves can go undetected for years, if they are found at all.
He cites the case of the rare white lemuroid ringtail possum. In 2008, after hearing reports the possums had gone missing, Laurance tried to find one in north Queensland. He and others concluded a heatwave three years earlier had killed many, pushing the species closer to the brink. The possums cannot survive for more than a few hours if temperatures rise above 30°C.
“Lots of people think heatwaves will be dangerous for things in cooler climates, but probably the tropics and tropical mountains will be where we lose most of our biodiversity,” Laurance says.
“We know that in heatwaves animals have a temperature threshold and above that, they start to die.
“There are silent crises happening all around us and it might be a few years down the track that we work out the skinks and frogs and plants that have died off.”
Heatwaves cause the most damage when they arrive on top of other stressors such as fragmented habitats, drought, disease and fire.
Last year scientists published an analysis of a 2011 heatwave in Western Australia. They found it had affected an area larger than Victoria – more than 300,000 sq km – spanning land and ocean.
An article published in the journal Scientific Reports said the heatwave caused “tree die-off and coral bleaching” as well as “terrestrial plant mortality, seagrass and kelp loss, population crash of an endangered terrestrial bird species, plummeting breeding success in marine penguins, and outbreaks of terrestrial wood-boring insects”.
Co-author Joseph Fontaine, an ecologist at Murdoch University, says: “We are getting more heatwaves and less time in between them. If you are a plant that’s close to your threshold then you’re going to die faster if it’s already hotter than it used to be.”
The heatwaves have a knock-on effect, he explains: “Here in the south-west we have these fantastic black cockatoos and they rely on the resources in the trees – the seeds – from eucalypts and banksia cones. If these events affect trees, then the resources are gone and the trees won’t produce food the following year.”
Ecologists are concerned by the speed of changes in the climate and how normally adaptable species are failing to keep up.
“Given that in Australia the climate is so variable and most of our animals and plants should be adapted to that, we start to ask: why is it that we are seeing so many impacts?” says University of Tasmania climate impact scientist Rebecca Harris.
“We keep talking about this as something that’s in the future, but we are seeing impacts now. Heatwaves and bushfires are what people are aware of, but there are many other impacts.”
Last year Harris led a study, published in the journal Nature Climate Change, looking at how Australia’s ecosystems coped with both long-term and sudden extreme climate change events.
“A single extreme event can be sufficient to cause irreversible regime shift or an ecosystem ‘tipping point’,” the study said.
Among the examples were the pencil pine forests in Tasmania devastated by fire in 2016; a “boom and bust” of extreme rainfall and heat in arid areas coinciding with massive outbreaks of rodents, and then bushfires; and in 2016 mangroves dying en masse along a 1,000km stretch of the Gulf of Carpentaria.
“We thought those undisturbed places would be more resilient,” says Harris. “But we showed that just wasn’t the case.”
by Graham Readfearn | The Guardian