They were once so common, swarms of Australian bogong moths almost seemed to “block out the moon” at certain times of the year.
Now, the bogong has been listed as endangered on the global red list of threatened species after crashes in its population in recent years.
The list, compiled by the International Union for the Conservation of Nature, was updated overnight with 124 new entries for Australian wildlife.
The addition of the bogong moth, famously seen in swarms at Parliament House in Canberra during its annual migration to the Australian alps, should be a wake-up call about declines in Australia’s invertebrates, the scientist Marissa Parrott said.
Parrott is a reproductive biologist at Zoos Victoria and one of the researchers behind the moth tracker website that was launched two years ago to try to map the migration routes of bogong moths and learn more about changes in the species’ populations.
Bogong moths were previously found in large numbers in parts of Queensland, New South Wales, the ACT, Victoria and South Australia.
“It is a really big step for the beautiful bogong moth to be listed as endangered,” she said.
“It is a really sad moment that a species that is so iconic to Australia, that people remember from their childhood as blocking out the moon, has now collapsed to the point of being listed as endangered.”
Other Australian species to be added to the red list include several other invertebrates, as well as plants and mammals.
Among them are Kangaroo Island species that suffered losses in the 2019-20 fires, such as the Kangaroo Island assassin spider, which has been listed as critically endangered, and the Kangaroo Island marauding katydid, listed as endangered.
The grey-headed flying fox, listed as vulnerable under Australian laws, has been given a vulnerable listing and the Arcadia velvet gecko, found in Queensland, has been listed as critically endangered.
Scientists have detected steady declines in numbers of bogong moths since the 1980s.
But in 2017 and 2018 that crashed to numbers so low the species was described as “undetectable” in the alpine regions where it used to arrive in spring in numbers as high as 4.4 billion.
The moths are so important as a food source to animals such as the mountain pygmy possum that when they arrive in the mountains they are the second largest energy source after the sun.
Researchers working with Gunaikurnai Land and Waters Corporation have also highlighted the species’ importance as a food source to traditional owners, with the discovery of microscopic remains of a bogong moth on a 2,000-year-old stone tool in a cave in Victoria’s alps.
The ecologist, Ken Green, has been monitoring bogong moths for 40 years.
He and other researchers were consulted by the International Union for the Conservation of Nature as part of the assessment and asked if they could quantify the size of the declines.
“They said are we talking 60%? Or 40%? And we said no. Three years ago we had a decline of about 99.5%.”
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Green recalls one set of surveys in the Canberra and Kosciuszko region in 2017 and viewing one cave that would typically house 17,000 moths a square metre. He said they could see just three moths inside.
Factors including pesticides and urban light pollution have been considered in relation to the decline in the species.
Green said Australia’s drought through 2017, 2018 and 2019 was likely the largest contributor. He said last summer recorded a slight improvement in populations but numbers were, at best, 5% of what they used to be.
Jesse Wallace is a researcher at the Australian National University writing his PhD on the bogong moth. He has been studying their migration patterns for more than four years to try to learn how the species navigates to the same locations each year.
He remembers the first surveys he did in 2017 at breeding sites in NSW where in previous seasons hundreds of moths would have been caught every night.
He said the endangered listing was both sad and unsurprising.
“I caught about 50 in five weeks. That was the first indication that there was a problem,” he said.
Jess Abrahams, the Australian Conservation Foundation’s nature campaigner, said the collapse of bogong moth numbers was affecting other species that rely on the moths for food.
“The bogong moth’s population crash – and its cascading impact on other species – should concern every Australian, as we all depend on the interconnected web of nature, which gives us drinkable water, pollinated crops and clean air,” he said.
He added the State of the Environment report, published every five years by the federal government, was due to be released soon and was expected to reveal further declines in the health of plants, animals and ecosystems across Australia.
Parrott said sightings of bogong moths could still be recorded at the moth tracker website and people could help the species on its journey by keeping outdoor lighting to a minimum.
She said so far this year the website had recorded 150 sightings but only one swarm.
“It really should be a wake-up call that we need to help our invertebrates,” she said.