Wild horses are destroying vegetation in NSW's Kosciuszko National Park and eroding vital water catchment systems flowing to Victoria and South Australia, a report says.
An estimated 14,000 horses in the Mount Pilot wilderness area of Kosciuszko National Park are destroying streamside wetlands, eroding banks, compacting soil, altering stream courses, overgrazing and trampling sphagnum bog, the Observations of Pest Horse Impacts report says.
"The impacts of pest horses in the pilot wilderness of Kosciuszko National Park were much greater and more pervasive than we had witnessed in over 40 years of intermittent observations," the report said.
Lead author, Australian National University adjunct fellow Dr Graeme Worboys, said there were just "too many horses".
"This is destroying the natural vegetation and erosion protection of these headwaters catchments and what's serious, with the numbers of pest horses increasing, it can only get worse."
Co-author Ian Pulsford, a mountains expert and former senior conservation and protected area manager, said the catchments were important as they fed water to the Snowy and Murray rivers, which delivered water to Victoria and Adelaide respectively.
Both men called for "urgent and effective action" to end the impact the horses were having on the area.
"(The horses) are excessively impacting Australian native animal habitats and they are severely degrading the headwaters of our most important rivers," the report says.