Experts say a NSW government decision to permit aerial shooters to cull the feral horses en masse will at last make a difference in the fight to protect one of Australia's most precious natural environments from their destructive hooves.

The notion of whittling brumby numbers in the park to a manageable level isn't new. Former environment minister Matt Kean heralded restricted plans to reduce their population from 14,000 to 3000 in late 2021.

 Yet in the intervening two and a bit years, and without the involvement of airborne marksmen, the herd has exploded to as many as 22,000.

That's despite National Parks and Wildlife Service data suggesting 3530 wild horses were removed by means other than aerial shooting during the same period.

Between last July and December alone, a further 1923 horses were taken out, 40 per cent of them by the newly-approved shooters.

Sniping from the belly of low-flying helicopters, professional bounty hunters are expected to help eliminate more than 20,000 animals by mid 2027, with repopulation taken into account.

It's a serious undertaking but one that wouldn't be possible without the tough call to allow aerial culls, according to Invasive Species Council Advocacy Director Jack Gough.

"This isn't easy, it isn't nice," he says.

"No one likes the fact we have to kill animals but the sad reality is that we've got a choice to make and that's between urgently reducing the number of feral horses or see the destruction of that incredible iconic landscape and the wildlife that live there."

Upper House hearings on the issue chaired by Animal Justice MP Emma Hurst continue with input from some Nationals, the Shooters and Fishers party, and One Nation.

However Labor, the Liberals and Greens have shown little interest, and the inquiry's findings will apparently have no bearing on the decision to cull from the air, with authority to proceed already handed over to NPWS.

To be less kind, Mr Gough says it's a sideshow.

"All the major parties are now on board to get the numbers down," he says.

"They all went to the last election with policies in favour ... and that reflects that the public is more educated, more aware and more concerned about the presence of the horses."

Retired Canberra University ecologist Don Fletcher reckons with the herd growing at 15-18 per cent, somewhere in the order of 6000 brumbies will need to go annually.

An average of 220 horses were passively trapped by NPWS and removed each year between 2003 and 2020, he says, with the period bookended by major bushfires which scorched large tracts of the park and also killed large numbers of brumbies.

Regardless, their numbers increased fivefold.

That program "achieved many times fewer horse removals than the number required to begin reducing impacts on national park values" and made "literally no difference to reducing the horse problem", Dr Fletcher says.

Mr Gough takes a harder line still.

"The best scenario would be that they're taking out more than 6000 in the first year," he says.

"The more we remove up front, the less animals that have to die.

"Delay, hindering, obstruction, if any of that comes into view, the consequence of that is more animals will be killed."

Just on 800 brumbies have been eradicated by shooters working from two helicopters since they were given the green light in October. The next expedition has been set down for March.

At a similar rate, at least eight aerial control operations will need to be staged over the coming months to keep pace with reduction targets. 

"It's a big increase on what's been done before," Mr Gough says.

"But in the context of feral animal control, in the last three years NSW has taken out over 250,000 feral animals using aerial shooting.

"At the scale we are talking, it's not a huge number to be removed."

Reducing horse numbers is not just possible but necessary, according to Greens environment spokesperson Sue Higginson.

"There is nothing pleasant about it but responsible land management demands it," she says.

"Everyday that the number of horses is not urgently reduced comes at a huge toll to the environmental and cultural values of the park. The reality is that we are talking about extinction of native species and irreparable ecosystem harm."

She insists there should be a "towards zero approach" rather than leaving 3000 brumbies in place. 

 There's no science behind the number, Mr Gough adds.

"It was created by political expediency, dreamt up by the National Party and agreed to by the Liberals.

"There will still be very large impacts at 3000, particularly considering that under the government's plan a third of the park will still be home to feral horses and in those numbers they can still cause significant damage."

Maintaining that level will also mean constant work with 15-20 per cent of the remaining population having to be removed every year.

"As soon as a political party comes in that lacks will or courage and is influenced by the vocal minority, there is a danger the numbers are allowed to get back and we have to start all over again," he says.

"The feral horses are cutting the sphagnum bogs, trampling those moss beds, they are trashing the headwaters of our major river systems and as long as they remain up there, they will continue to do that."

The area where it may prove hardest to conduct the cull, above the alpine tree-line, is flushed in summer with a profusion of wildflowers and delicate plants that regulate the slow release of melted snow into the mighty Murray-Darling Basin. 

It's hard to imagine opponents of the horses will be quieted so long as they're allowed to churn the precinct's thin soils and further threaten the habitat of the rare corroboree frog and other endangered species.

"It's not a place that can accommodate large, heavy animals with hard hooves," Mr Gough says.

"The soft-footed native animals it is designed to house get no bigger than the biggest male kangaroos."

Meanwhile, an estimated 4000 pigs and deer have been shot in Kosciuszko National Park in the past several years yet the eradication of the latter is also likely to be stepped up with numbers persistently rising still.

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