Updated
In the wake of Adelaide's hottest day on record, which came soon after the end of Australia's third hottest year on record, arguments will continue about climate change and its impacts.
But
according to Professor Ary Hoffmann from the University of Melbourne,
definitive signs climate change has landed can now be observed in some
backyards.His team of academics and ecologists have released a paper detailing the land-based effects of climate change over several decades, uncovering flora diebacks and extinctions, insect booms and out-of-whack orchids and butterflies.
"Everyone knows about coral reef bleaching, but very few people, I think, are aware that we are also seeing forests suffering from heat stress along with other terrestrial ecosystems," the professor said.
"There's certainly some evidence some orchids are coming up much earlier as it gets warmer, and there are also changes happening in arrival times of some insects.
"But if a flower pops up at the wrong time, particularly an orchid, their pollinators are not around and they're not going to be successfully pollinated.
"You get that sort of disconnect between the pollinator and the flowering time and that can lead to severe consequences for those species."
Fluctuating weather conditions a 'challenge'
The ABC reported last month that erratic plant flowering in South Australia had led to reduced bee numbers and a forecast 80 per cent drop in honey yield.
"That reinforces something that's really important," Professor Hoffmann said.
"It's the fluctuation in conditions, not so much the fact they're getting warmer, that makes everything become more variable, which is a challenge for species."Some common brown butterflies were also appearing earlier, while in Canberra annual swarms of bogong moths had more than halved, "which some people think is related to climate change and the dry conditions that are happening".
"But in that particular case, there might be other explanations," Professor Hoffmann said.
Less-reported issues emerging
Beyond backyards, there have been extensive signs that climate change is having a negative effect on forest ecosystems.This includes Jarrah forests in Western Australia which are dying due to a lack of rainfall and poor water retention in the soil, while eucalyptus forests on the Cumberland Plain west of Sydney are suffering dieback.
Professor Hoffmann said a common psyllid species favourable to warmer weather had repeatedly "blown up" in the forests, which had led to defoliated canopies, dieback and tree mortalities.
"They [psyllids] can effectively defoliate trees quite quickly once it happens," he said.
"In the Northern Hemisphere there are massive examples of forest deaths resulting from insect attacks, particularly bark beetles.
"We haven't seen that yet, but we are starting to see the first evidence of insect outbreaks occurring in response to climate change and I think that's quite worrying."
Cushion plants dying back
His team also reported cushion plants on Macquarie Island were dying off due to drying conditions in what was usually a wet and misty environment, leaving them vulnerable to pathogens.It also reported significant changes in vegetation composition across areas of the Victorian alps along with increased insect invasions and a higher frequency of bushfires that had affected seed production and re-sprouting ability.
Other case studies reported in his team's paper, published in the peer-reviewed Austral Ecology journal during October, included:
- local plant extinctions
- size changes in birds
- shifting biotic interactions that threaten communities and endangered species
Climate effects becoming more definitive
Professor Hoffmann said it had historically been hard to directly attribute events to climate change, but with multiple decades having now passed since studies began, the volume of information had increased and predictions made under climate modelling were ringing true."The argument has always been, 'We've had extreme conditions in Australia, drought and hot conditions, so how can you attribute a particular condition to climate change'," he said.
"But we've been tracking these changes for 10, 20, 30 years now, so it's not just one event but a repeated pattern.
"Where you see eucalyptus forests in the alpines burning again and again due to heat events, or psyllid attacks occurring again and again as seasonable conditions change, then you become confident about the validity of the cases."
He said it was time to do something more dramatic to conserve threatened species, such as protecting "refuges" where a species might be thriving due to a location's unique topography.
"We also need to think about the bigger landscape and how we make sure that we keep canopy cover.
"There are many species, for instance, where we have different genotypes that have adapted to different climates, and maybe there's a case to move those genotypes around the country."He pointed out that Adelaide's climate in a few decades would likely resemble today's climate about 300 kilometres north of the city where endemic plants have adapted to hotter and drier conditions.
"The extremes are going to build up, so when you're doing revegetation, rather than sourcing plants locally, perhaps you should be sourcing genotypes and even your species from the north," Professor Hoffmann said.
"It's about vegetating now for the future."
No comments:
Post a Comment