On another hot, dry day a few weeks ago, Joe Fontaine stood in a eucalyptus forest in Western Australia, devoid of the usual din of bird calls.
‘I heard the crunching of the trees,’ said Fontaine, a forest ecologist at Murdoch University in Perth.
Peeling back the bark, several pinky-sized beetle larvae are gnawing at the dead wood. He said when trees are stressed, the beetles take over.
The forest canopy above Fontaine is turning brown. Trees over a hundred years old are almost lifeless. Some of these giant tamarisk eucalyptus may survive, but some do not.
In the wake of drought and intense heat, the scene is repeated across more than 1,000 kilometers (620 miles) of forest and coastal scrub in the state’s southwest.
Many of these ecosystems are dominated by eucalyptus trees such as Jarrah and Eucalyptus marigold, and coastal scrub is populated by banksia, a species found nowhere else on Earth.
Fontaine’s inbox is filled with photos of dead and dying shrubs and trees. One of the earliest signs came in February, when Perth’s street trees began dying after several days of record temperatures above 40 degrees Celsius. The city experienced its driest six months on record, from October to March.
Similar conditions occurred in eucalyptus forests in the state’s southwest in 2010 and 2011, a dieback event that prompted more than a dozen studies. Drought-stricken forests are hit by fires a few years later, releasing carbon dioxide, raising concerns that forests may transform into carbon sources rather than carbon storage.
Dr Katinka Ruthrof, a senior research scientist at the state government’s Department of Biodiversity, Conservation and Attractions, said the current deaths had similar characteristics to the 2011 incident. The department is using imagery from satellites, fixed-wing aircraft and drones, as well as on-site inspections, to assess the damage.
When conditions improve, some plants may be able to survive and resprout, but many may die, she said. It depends on how long the dry season lasts.
Ruslov said changes in habitat structure and composition will have knock-on effects for some species, including providing habitat and food resources for wildlife.
Dr Mark Harvey, curator of spiders, millipedes and centipedes at the Western Australian Museum, said south-west Western Australia has hundreds of invertebrate species found nowhere else.
The southwestern corner of Western Australia has been isolated from the rest of the continent for the past three million years. This allows species to develop in isolation.
These species have been accustomed to wet conditions for thousands of years, he said.
We are very concerned about this drying event. If animals don’t have coping mechanisms like digging burrows to escape the heat, they will die.
They are locally extinct. They have nowhere to go. Even if the habitat recovers well again, it will take thousands of years to recolonize. The prognosis is not good.
Fontaine said it was distressing to see the death in the bush and forest and he was worried about the wildlife.
I’m now trying my best to find leather to make people go, oh shit, we need to record this, he said.
Clear climate signals
Atmospheric scientist Dr Kerin Hawke, a colleague at Murdoch University in Fontaine, said trees and plants in the region were accustomed to a Mediterranean-style climate, with cold fronts from the ocean to the south bringing ample rainfall in winter.
But research shows these fronts have moved further south, away from the coast.
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“These fronts are no longer reaching as far north as they are, which means there’s less rainfall from the fronts and when they get to us, they’re not as intense,” she said. Due to climate change, we are seeing increasingly hotter days. Vegetation is not adapted to such low rainfall.
Rainfall over the past 12 months has been well below average across much of the Western state, with some locations seeing the lowest rainfall ever recorded, while temperatures were the highest on record.
It was a perfect storm of temperatures and rainfall. But what stands out are the high temperatures we experienced early on, she said, pointing to heat waves in September and November.
The conditions in recent months are part of a pronounced drying phenomenon that scientists have observed in the region since the 1970s.
Cold-season rainfall has dropped by 20% over the past two decades compared with 1901 to 1960. Very wet years have almost completely disappeared.
About half of the change is attributable to increases in greenhouse gas emissions, which may be an underestimate, according to a study led by Met Office scientists.
Research shows that even with rapid reductions in greenhouse gas emissions, the drying trend is likely to continue for the rest of the century.
Dr. Michael Grose, a climate scientist at the Australian Government’s Commonwealth Scientific and Industrial Research Organization, said that scientists had discovered drought trends as early as the 1970s.
He said it was one of the clearest and strongest signals of average rainfall anywhere in the world.
fire and fear
There appears to be little relief from the situation, with hotter and drier weather expected over the next three months.
Fontaine said the risk of bushfires was rising due to the massive die-off of surrounding vegetation.
He said fire departments need to be cautious as they conduct prescribed burns to try to reduce the risk of large, out-of-control fires.
About 430 kilometers south-east of Perth is Walpole, where David Edmonds owns a beef and orchid farm and works for the Walpole-Nonalup National Park Association. Walpole-Nornalup National Parks Association).
He grew up in Walpole and has seen parts of the wilderness, including the 90-metre-tall Cowrie trees, turn brown this year.
The rain stopped really early. He said the die-off of the granite outcrops became apparent.
It’s sad. Are you worried if this is a one-time thing or will it be something more common. We can’t start watering the tree.
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Image Source : www.theguardian.com