Environmentalists warn feral horses could be the final nail in the coffin of threatened native species, but state governments are unable to agree on how to control the ever-growing population.
A federal parliamentary inquiry is examining the impacts and management of feral horses in the Australian Alps, an area which straddles the borders of eastern Victoria, southeast NSW and the ACT.
Invasive Species Council advocacy manager Jack Gough told the Senate committee there were between 14,000 and 24,000 feral horses in Kosciuszko National Park as of 2022.
"This is a national park, it is not a horse paddock - but right now it is becoming a horse paddock," he said.
The NSW government recently opened consultation on a controversial management plan that would allow shooting of the horses from the air to control their numbers.
The state's approach is at odds with that of the ACT and Victoria, where feral horses are typically culled through ground shooting but aerial shooting is also allowed.
Authorities in NSW discourage culling and prioritise passive trapping and rehoming after a 2018 law was passed under the then-coalition government to protect the "heritage value" of the horses.
Mr Gough said the current rate of removals by NSW officials of 1000 per year would lead to numbers growing to more than 32,000 horses by June 2027.
To keep the population stable, 2800 horses needed to be removed annually, while about 6000 horses needed to be taken out each year to hit a target of 3000 horses by June 2027, he said.
Environmentalists argue the horses are impacting native animal habitat and important waterways as well as changing the landscape significantly.
"Feral horses could be the final nail in the coffin for threatened native species, sending them extinct," Mr Gough said.
Nature Conservation Council of NSW representative Clancy Barnard said public sentiment was also changing in favour of better feral horse management.
"No one likes to see animals killed, but the sad reality is that you have a choice to make with urgently reducing the number of feral horses or accepting the destruction and its impact on ecosystems and habitats," he said.
ACT Environment Minister Rebecca Vassarotti said the three jurisdictions needed to work together, but tensions between them and different feral horse management approaches presented a significant problem.
Without a coordinated and cohesive approach, the animals would cause "catastrophic consequences" for Australia's environment and biodiversity, she said.
NSW environment department deputy secretary Rachel Parry conceded the state's current approach to feral horse management was insufficient but was unable to detail how authorities could best move forward.
Brumby advocates say it is possible to protect the environment and control horse populations.
The Australian Brumby Alliance supported procedures to manage horses and acknowledged their impact on the environment.
But they would not support practices which resulted in brumby extinction.
"It's very hard to discuss sustainable numbers with the opposition, because they only want to talk about getting to zero numbers and there is no in-between," alliance representative Jill Pickering said.
"We believe in dialogue and discussion but we're now excluded from just about everything."
