The remarkable insect, which migrates more than 1000 kilometres on its journey from Queensland to Victoria, once flocked to Canberra in such density swarms were known to settle inside Parliament House, the bright lights on the hill often leading to their demise.

In the early 2000s, thousands of bogongs could be found at Mount Gingera, the Brindabella cave walls thick with dormant moths seeking respite in alpine areas over warmer months.

Today, almost 99.5 per cent of the billions of bogong moths that existed in Australia this decade have disappeared.

The bogong has since been elevated to The International Union for Conservation of Nature Red List of Threatened Species, where it is currently listed as endangered.

While the decline initially occurred steadily, a dramatic drop occurred from about 2017, when much of eastern and inland Australia, as well as parts of South and Western Australia, suffered from severe drought.

Pesticides and light pollution from Canberra and Sydney, as well as mismanagement of the Murray Darling system, are all thought to have contributed to their demise.

Ben Keaney, an expert on the species and researcher at the Australian National University, has been unable to locate a single bogong in his field trips to Mount Gingera in the last two years.

"It's absolutely shocking," he said. "The numbers dropped precipitously."

As with any upset to ecosystem equilibrium, the loss of the little moth has far-ranging complications.

Dr Keaney said several species rely on the bogong moth for sustenance, including the critically-endangered pygmy possum and two species of obligate nematodes.

"The bogong moth not going into the Alps areas has really major implications on glider populations or other vertebrates that might feed on them," he said.

"Their populations will also be reduced and that will have other trophic cascades into the ecosystem and further down as well."

While the length and severity of the 2017-2019 drought may have been difficult to predict, Dr Keaney said there were plenty of warnings when it comes to the decline of the bogong moth.

Dr Keaney said a researcher named Ken Green found evidence the moths were carrying arsenic into the mountains in the early 2000s, likely from insecticides.

"These days in Australia there's some questions about the use of neonicotinoids," he said. "In Europe, they call it the bee killer."

Dr Keaney said awareness of damage from light pollution was also well known before changes were made to the wavelength of Parliament House lights.

He said limitations on water flowing from the Murray to surrounding floodplains also negatively implicated bogong moth larvae.

"There were red flags," he said.

"Not the least of which is climate change and that's something people have been talking about since the 90s, even earlier."

Recently, the ACT government's environment directorate brought together the country's eminent bogong moth experts in the hope of better understanding how things got so bad so quickly, with a goal of devising an action plan for improving the survival of the species.

A workshop next month will invite traditional custodians to share their knowledge of the moth, which has been identified as an important food source for Indigenous Australians up to 2000 years ago.

Dr Keaney said while the bogong moth's widespread distribution meant there was hope, it was difficult to predict an outcome at this early stage of population collapse.

"We need to think how to make our cities and rural areas more bogong moth friendly," he said.

"They are an iconic species and I think Australian society has the will to protect and save them."

Land clearing was identified in the State of the Environment report, alongside invasive species and ecosystem modifications, as the biggest risk to threatened plants and animals.

Clearing has been implicated in the listing of 60 per cent of threatened species, with 93 per cent of land habitat cleared between 2000 and 2017 not referred to the Australian government for assessment.

A draft action plan for ACT's mature native trees was released earlier this year following dramatic decline largely due to land clearing, which saw them added to the key threatened species list in 2018.

It is estimated more than 21,000 trees were lost across the ACT between 2015 and 2020, or more than 6 per cent of urban mature trees.

New developments in Coombs, Denman Prospect, Throsby, Taylor, Wright and Whitlam accounted for the largest losses.

Larry O'Loughlin is a former Executive Director of the Conservation Council ACT. He said the message from the national report that Australia's environment was bad and getting worse was a wake-up call for the ACT.

"We continue to face the ongoing death of nature by a thousand cuts, mostly through urban development and associated infrastructure proposals," he said.

Mr O'Loughlin pointed to the ACT government-sponsored proposal for a solar battery facility in Central Molonglo. He said the development will involve clearing five hectares of critically endangered yellow-box-redgum woodland.

"On the other side of Canberra there is a proposal for a crematorium, which many think we don't actually need, that will involve the removal of a significant number of mature native trees, as well as the younger re-growth which could eventually become mature trees.

"While the site is quite degraded, its location next to Callum Brae Nature Reserve and the connectivity value to the Mount Mugga Mugga Nature Reserve, it is a prime example of a site that can and should be restored.

"We also have on the table an Urban Forest Bill that seems to indicate that mature native trees can be removed if the developer proponent is willing to pay a fee."

Mr O'Lougholin said if Canberra doesn't heed the call from the State of the Environment report and continues to destroy and degrade habitat it's facing a similar report in five years' time.

"The ACT is not separate from the rest of Australia in needing to step up and do better," he said.

The gang-gang cockatoo, the animal emblem of the ACT, was officially listed as a threatened species this year after a rapid decline in numbers exacerbated by climate change.

A national plan is being developed to save the bird researchers are just recently learning more about, with bushfires thought to have contributed to a 70 per cent decline in populations over the last 25 years.

The gang-gang is one of many Australian bird species found to be at risk, with the State of the Environment report finding threatened populations declined by an average of 60 per cent between 1985 and 2018.

The Canberra Ornithologists Group has been documenting bird populations in the ACT since the 1970s, with the aim of promoting the conservation of habitat.

A recent article written by several members found of 129 species surveyed over almost 20 years, 32 showed a "statistically significant decrease in reporting rate", including 28 native species.

The analysis found species such as the tree martin and fuscous honeyeater may need considering as threatened under the ACT Nature Conservation Act and already listed species including the hooded robin may need upgrading.

Neil Hermes, Ornithologist Group president, said species needing attention were those that didn't favour large parks like Namadgi, common places like Lake Burley Griffin or even backyard gardens.

He said the species preferring edges of disturbed country between nature reserves and farmlands of the past were in the greatest trouble.

"This is an area where there's been big impacts in terms of the clearing of timber for firewood, the clearing of timber to make it better for pasture country," he said.

"It's a habitat that we're losing significant areas of in the ACT because we're losing the edges."

Mr Hermes said the landscapes had been changed so much over the centuries that some species' survival did require intervention, the question will be what sort.

"Just planting trees is not necessarily a solution, or just taking a broad view about the use of fire is not necessarily the solution," he said.

"It's going to be more sophisticated than that.

"To protect some of these birds we're going to have to understand exactly why it is their declining and we'll have to come up with quite refined ways of finding protections."

Mr Hermes said informed action plans would be required for many other animals and plants too, particularly when they compete for survival in the changed environment.

"In many of our reserves we've been removing the shrubby weeds that have invaded our parks over the last decades," he said.

"On some occasions the removal of those woody weeds removes the very protection that some small birds like speckled warblers need to keep away from predators," he said.

"That's not to say we should leave the woody weeds, but on the other hand, we've got to protect the speckled warblers.

"It's a juggling act."