There have been 26 car crashes involving brumbies since 2003

The horses ­occupy 48 per cent of the park

Remaining horses will be kept within three low-impact areas

The animals will be shot, trapped or subjected to fertility control measures

Government scheme will see 6000 brumbies become 600 in 20 years

Wild brumbies, who have been a staple feature of the Snowy Mountains since the 1930's, are under threat as a controversial NSW government plan aims to cull the population by 90 per cent.

The plan comes in a bid to save the Kosciuszko National Park after a steep rise in the population began to threaten native wildlife.

Almost 6000 wild horses will be killed under the plan with half of the population set to disappear within the next decade.

The population of the brumby is estimated to be increasing by 20 per cent every year, which has prompted the government to consider more radical measures of population control.

The animals will be shot, trapped, or subjected to fertility control measures. Culling is set to continue over the next two decades until the population has dwindled to 600, and these horses will be kept within three low-impact areas within the alpine park.

The details of the proposal have been released in the Kosciuszko Draft Wild Horse Management Plan 2016 which was placed on public exhibition on Sunday.

The NSW National Parks and Wildlife Service (NPWS) says horses are damaging to the natural structures of the national park, such as riverbeds, streams, natural bogs, wetlands and soil structure, as they trample the ground when they feed or look for water.

The horses have spilled over into endangered wetland, and their hard hooves are damaging the delicate ecosystem, which could lead to the loss of some native animals.

Small native mammals, reptiles and amphibians potentially affected by habitat impacts include the broad-toothed rat, the alpine water skink, and the alpine tree frog.

The NPWS also outlined how wild horses such as brumbies can foul waterways, creating a risk to domestic and industrial water supplies.

The horses pose a potential biosecurity risk and can spread cryptosporidium- an infection of the bowel carried by a parasite - and diseases such as equine influenza, African horse sickness and tick fever, which can have a devastating impact on local farmers.

The brumby arrived in Australia on the First Fleet. Only seven survived the harrowing journey. The horses are now found all through the nation - except in Tasmania.

Efforts to re-home brumbies that are not killed have been included in the long-awaited plan, though take-up rates on similar schemes have been low, and the majority of horses end up slaughtered.

NSW Environment Minister Mark Speakman told the Daily Telegraph that wild horses would always be part of the cultural heritage of the Snowy Mountains, but the numbers were unsustainable with the fragile alpine and sub-alpine ­environment being damaged.

'Wild horse management is an emotive and complex issue. There are diverse opinions in the community. It is clear, however, that the broader community values the unique environmental values of Kosciuszko National Park and looks to NPWS to protect these values,' he said.

The plan said the horses ­occupied 48 per cent of the park, with 26 car crashes involving brumbies since 2003.