Abu Dhabi, UAEWednesday 2 December 2020

Environment

‘We don’t know what we’ve lost’: the small-scale tragedy of the Australian bushfires

The survival of a tiny species of ancient trapdoor spider hinges on what happens next

Driving down the road that cuts through the heart of the Stirling Range National Park is at first glance like looking at a before and after picture.

On one side of the rutted gravel track, the bush is green and lush with thick undergrowth and birds darting overhead. On the other side, all that is left is ash and charred black sticks. Rugged peaks rise up, bare and exposed.

In the week between Christmas and New Year, a blaze sparked by lightning burnt through 40,000 hectares of the park, which is among the planet’s most important biodiversity hotspots.

With the world’s attention on the devastating fires burning out of control near major cities and towns on Australia’s east coast, the fire in a sparsely populated part of remote Western Australia barely ranked a mention beyond the local media. Yet, several of the park’s endemic flora and fauna species are now in peril.

What we’re concerned about at the moment is those fires becoming closer and closer and the little pockets that are being burnt are getting more restricting of populations

Dr Mark Harvey

Among them are tiny spiders that live quiet lives in shallow burrows dug into the earth between the peaks and valleys. Trapdoor spiders, which look something like miniature tarantulas, are a living relic surviving from a time hundreds of millions of years ago when this land mass was part of the ancient supercontinent of Gondwana.

Described as “the most fiercely solitary of all spiders” by the late Australian arachnologist Professor Barbara York Main, trapdoors live shy and cloistered lives. This can make them especially vulnerable to extinction from habitat destruction, climate change and bushfires.

Main, who died in 2019 at the age of 90, was known as Australia’s ‘Lady of the Spiders’ after a 1981 documentary that David Attenborough made about her. She described more than 70 species and genera of spiders and famously studied a trapdoor matriarch known as No.16, which became the oldest spider in the world before it was killed by a wasp at the age of 43, making headlines as far away as London and New York.

At least 13 species of trapdoor spiders are endemic to the Stirlings, many of which were discovered by Main. Five of them are of conservation concern, including the Eastern Stirling Range pygmy trapdoor, or ‘Bertmainius colonus’, which belongs to a genera named after the arachnologist’s late husband, zoologist Bert Main.

After leaving its mother’s burrow, a female trapdoor spider will dig a hole, cover it with a cleverly camouflaged silk-hinged lid, then stay there for years, occasionally luring in prey that comes too close, and rarely moving more than a few metres from its birthplace. This behaviour means the spiders have existed in the same relatively unchanged patches of earth for millions of years, with some entire species confined to single gullies.

The Stirlings themselves are unusual and ancient -- a collection of peaks formed from hard dolomite rising from an otherwise flattened, dry scrubland.

“We see things like spiders and insects and plants and various other creepy-crawlies that survive in the Stirlings that are species that don’t occur anywhere else,” Dr Mark Harvey, Senior Curator of Arachnology at the Western Australian Museum, tells The National. “They have evolved in isolation and they are restricted to these peaks now.”

It is too early to know if any species have been wiped out – or are under existential threat - after the latest fires. Detailed surveys will have to be carried out and it could take years to understand the full impact.

“If the fires have got into those gullies then those populations are going to be affected at the same time,” Dr Harvey says. “But until we get in there and see how far they’ve got into the gullies and how intense the heat was we won’t know.”

The same traits that make the spiders of the Stirling Ranges so unique also means they are in increasing peril as Australia’s bushfires grow in frequency and intensity.

A burnt trapdoor spider burrow in the Stirling Range National Park, Western Australia. Courtesy: Leanda Mason
A burnt trapdoor spider burrow in the Stirling Range National Park, Western Australia. Courtesy: Leanda Mason

“Hot, intense bushfires are dangerous for trapdoor spiders in any context,” says Dr Leanda Mason, who studies arachnids at Curtin University in Perth and wrote her thesis on conservation threats faced by trapdoor spiders.

If spiders are not killed directly by the fire, they may suffer subsequent predation by creatures including scorpions and centipedes, after the lids of their burrows are burnt off, or die later from starvation in a decimated ecosystem.

“More specifically in relation to the Stirling Ranges, the trapdoor spiders vary considerably in terms of size and depth of burrows,” Dr Mason says. Pygmy Trapdoors have shallow burrows, meaning they are at higher risk of being burnt in the fire front.

Bertmainius monachus, another small species with shallow burrows, is also at high risk of extinction because a bushfire could easily wipe out the remaining few or reduce the population to the point where it cannot recover.

“If it hasn't already gone extinct since the last survey,” Dr Mason adds.

The second major fire in two years

The “before picture” on the north side of the park is deceptive to the untrained eye. The lush greenery is regrowth from another fire that swept through the area just two years ago, heavily impacting several species. The full impact of that fire was still being examined as yet another major fire event struck.

While much of the Australian landscape is dependent on regular burning for regeneration and propagation of many species of plants, to have two major fires in the park in such a short space of time is potentially devastating.

Trapdoor spiders tend to take a long time to reach sexual maturity, which means it could take hundreds of years for populations to recover, if they do recover

Dr Leanda Mason

The Stirlings tend to create their own weather system, with lightning frequently starting fires. But climate change has changed the nature of those fires, with a dried out and drought-stricken environment meaning they can burn more frequently, hotter, and for longer, destroying vast areas each time.

“The Stirlings have burnt consistently for millions of years,” Dr Harvey says. “I was in the Stirlings once and looking at Toolbrunup when a bolt of lightning hit the top of it and it was probably the most amazing thing I’ve ever seen.

“Dry lightning starts fires. The issue is the intensity and the regularity of those fires. In the past, they have been spaced apart which means the landscape, the vegetation and the animals have been able to recover.”

“What we’re concerned about at the moment is those fires becoming closer and closer and the little pockets that are being burnt are getting more restricting of populations.”

Part of the problem for trapdoor spiders, Dr Mason says, is that they live longer lives than most other arachnids, taking years before they get around to breeding and replenishing their species.

“Trapdoor spiders tend to take a long time to reach sexual maturity, which means it could take hundreds of years for populations to recover, if they do recover,” she says.

Too small to matter?

As we drive along the road north from my family’s hometown in Albany, the familiar peaks came into view. But this time it’s different. As we enter the Stirlings we pass through kilometre after kilometre of blackened, denuded land.

With most of the park closed to tourists to allow the land to regenerate, including the popular hike to the top of the highest peak, Bluff Knoll, the roads are quiet for this time of year. We pass a grain truck heading in the opposite direction from the wheatbelt towards Albany’s port and a couple of emus on the side of the road, seeking out the few tender sprouts of regrowth available.

The experience is a stark reminder of the challenges faced in rural areas across Australia, with the environmental and economic tolls still being counted. A billion animals were estimated to have died in the unprecedented fires that burnt through millions of hectares, and images of charred kangaroos and koalas will haunt the country for years to come.

Those are the most visible of the tragedies. What the plight of the trapdoor spiders points to is another, quieter, battle to save the species that might otherwise slip away unnoticed, too small to matter.

'More species than we could hope to name in our lifetimes'

Back in Perth, at a nondescript cluster of large sheds tucked into an industrial area at the fringes of the city, Dr Harvey leads me through WA Museum’s huge specimen storage facility. He points out the stacks of shelves that store the most complete record of the state’s known arachnids - more than 250,000 specimens in all. Bottle after bottle after bottle packed with spiders and scorpions preserved in ethanol.

There are species in here that have not even been described yet – and it is unlikely they all could be any time soon. This is the physical representation of a major issue when it comes to preserving invertebrate diversity in Australia – there are too many species to count and too few qualified people to count them. The taxonomic backlog is immense.

A female Cataxia colesi. Courtesy Western Australian Museum
A female Cataxia colesi. Courtesy Western Australian Museum

“I think that’s the tragedy – Australia is a mega diverse country, there are hundreds and hundreds of thousands of undescribed species and we find more species every year than we could ever hope to name in our lifetimes,” Dr Harvey says.

“That’s the big challenge – we don’t know what we’ve lost. If it’s not on a list, if it’s not captured somebody’s attention, it’s hard to get funding for it.”

On the map

On Thursday, April 23, the Wildlife and Threatened Species Bushfire Recovery Expert Panel released a priority list of 191 invertebrate species known or presumed to have been severely impacted by the 2019-20 fires. They include freshwater mussels, shrimps, burrowing crayfish, land snails, spiders, millipedes, bees, dragonflies, bugs and butterflies.

However just five invertebrates have so far been included in the Australian Government’s list of 119 species considered to be a high priority for urgent intervention after the bushfires. Three of those are from the Stirling Ranges - the Eastern Stirling Range Pygmy Trapdoor Spider, Banksia brownii Plant Louse and the Banksia Montana Mealybug.

“The reason the Stirling Ranges is on the map in terms of these fires is because we understand what’s going on,” Dr Harvey says. “But you can’t say that for Eastern Australia because the extent of the fires is massive.

“In south-eastern Australia there’s going to be hundreds, even thousands of species that are undescribed.”

Dr Mason sees an injustice at play when it comes to protecting invertebrates.

“Although maintaining natural biodiversity is often referred to as being a high priority in conservation, those clades which contribute the most biodiversity, are also those that receive the least amount of funding,” she says. “Some argue that by conserving the larger animals, or even the landscape, that by default the species without funding will be protected and managed too.

“However, doing numerous, very similar studies on the same charismatic species does not seem the most efficient use of resources to preserve biodiversity.”

A fighting chance

The trapdoor spiders of the Stirling Ranges are luckier than most invertebrates. They were put on the conservation map by Main and her legacy lives on through the work of the scientists now working diligently to keep them there.

Discussions are ongoing about how to protect them from future bushfires. One option is to start breeding populations elsewhere, but the slow life-cycle of the trapdoor spiders makes this challenging. Another is for closer collaboration between scientists and fire authorities to prioritise protecting patches of bushland where the most vulnerable species live.

Dr Harvey says this has already worked successfully at least once in the past in the Stirlings, with firebreaks put in place to protect a gully at the base of Talyuberlup Peak that is home to a population of pygmy trapdoors.

“That’s probably the first time in the world I’ve ever heard of that fires have been managed to actually conserve an invertebrate species," he said.

Main once said in an interview that as a child growing up in the wheatbelt she became interested in small things, insects and spiders, because they were “on a scale I could relate to.”

Now, as environmental conditions worsen year after year with the changing climate, the question is whether Australia will prioritise its smallest creatures and give them a fighting chance in the battle for survival.

Updated: April 28, 2020 11:21 AM

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