New research looking at the impact of feral horses in Australia's alpine parks system has concluded that aerial culling is needed to ensure the survival of native ecosystems.

Key points: The research paper backed studies into controlling feral horse populations which consistently come to the same conclusion

The research paper backed studies into controlling feral horse populations which consistently come to the same conclusion $10 million spent removing livestock and restoring alpine areas between the 1960s and 1980s is being wound back by horses

$10 million spent removing livestock and restoring alpine areas between the 1960s and 1980s is being wound back by horses A NSW aerial cull of 606 horses in 2000, a method supported by the RSPCA, resulted in only one incident of prolonged suffering

The peer-reviewed research by a group of 25 scientists found feral horses cause "widespread environmental degradation, destroy ecosystems, eliminate populations of native species and spread weeds".

They argue it can only be successfully managed by culling, as is practised with most other feral animals.

Don Driscoll, a professor of terrestrial ecology at Deakin University and a co-author of the research paper, said studies into controlling feral horse populations have consistently come to the same conclusion.

"It's really only using aerial culling that you can control horse populations. National Parks really aren't compatible with these very large, introduced species," he said.

"The science that we published … all points in the same direction.

"It shows importantly that even very low numbers of horses cause a level of damage that accumulates over time."

Impact on native flora and fauna

A meta-analysis of ecological studies from around the world found that feral horses are the single largest cause of widespread environmental degradation throughout alpine parks.

The scientists argue that managing feral horse populations requires a conscious ethical trade-off. ( Supplied )

Between the 1960s and 1980s, more than $10 million was spent removing livestock and restoring alpine areas.

"Because of the inaction of the NSW Government … the incredible restoration work done between the 1960s and 1980s could be undone by expanding populations of feral horses," he said.

Studies found feral horses contributed to a 32 per cent decline in soil stability, a 34 per cent decline in plant biomass, and an overall decline in the quality of an environment by 16 per cent.

"Scientists were at pains to consider what sort of animals were causing the damage, and what they found was that wherever horses were the dominant herbivore they were essentially the only, or the major, cause of the damage," Professor Driscoll said.

Feral horses often compete with native wildlife for food and water, and damage by horses to water streams had implications for water quality.

Ethical considerations

An aerial cull in 2000 conducted in Guy Fawkes National Park resulted in a public backlash against the practice after distressing images of a horse experiencing prolonged suffering were shown.

However, an independent report cited in the research paper found the images were an isolated event that did not reflect the overall success of the program.

The report found that of the 606 horses killed, there was only one incident of prolonged suffering.

63 per cent of horses were killed instantly and the average time to death was 19 seconds for the other 37 per cent.

Professor Driscoll argued that aerial culling had fewer animal welfare concerns because it is fast and minimised horse stress, particularly when weighed against mass horse starvation events that occur during periods of drought and floods.

"The cull at Guy Fawkes National Park was undertaken because horses were starving to death after a fire there," he said.

"Now, in Kosciuszko National Park and in parts of Victoria last year, we've seen these feral horses starving to death and suffering slow, long, miserable deaths because neither government has been able to implement aerial culling."

A mass brumby death was discovered in a remote location near Santa Teresa. ( Source: Facebook/Ralph Turner )

Controlling populations

Aerial culling is used to manage feral horse populations in most other states and is supported by the RSPCA.

However, the issue has become contentious in south-eastern Australia.

Last year, the NSW Parliament legislated to protect feral horses in Kosciuszko National Park.

Professor Driscoll said other methods of controlling numbers — such as rehoming, fertility control, trapping and mustering — have all, in one way or another, proved ineffective in the long term, and expensive.

"If you're just doing trapping and mustering you can't take away enough horses, fast enough, to stop the expansion of these populations," he said.

Similar trapping and rehoming programs in the US have proven unsuccessful in managing horse numbers which, according to a demographic study, are at a critical tipping point.

Professor Driscoll anticipates a similar problem in Australia's alpine areas.

"No horses have been removed from Kosciuszko National Park since 2017 … and it's devastating for the environment."

"We've had horses spreading up over those highest alpine areas … that the Government has spent over $10 million rehabilitating after cattle and sheep were taken out."

Cultural considerations

The affiliation between feral horses and an early colonial settler identity has been mythologised in films, novels, poetry, and notably in the opening ceremony of the Sydney Olympic Games in 2000.

Australian bush lore, made particularly famous through the poetry of AB 'Banjo' Patterson, has created an inaccurate cultural value, according to Professor Driscoll.

"There's a few myths — the idea that brumbies in Kosciuszko National Park were related to the light horses that went off to World War I, that's a complete myth," he said.

"The only real cultural value is the local cultural value.

"One way of managing that is for horses to be taken out of the national park and established on private property … in an area that isn't dedicated to nature conservation."

Professor Driscoll argued that a substantial restoration program is necessary, in addition to the removal of feral horses, to prevent environmental degradation and erosion.

"An integrated restoration program is going to first involve removing the horses so that the threat is no longer there," he said.

"The damage the horses do now is going to cost millions of dollars, and the longer it's left the more damage those horses are going to do."