Letting thousands of brumbies roam wild through the Snowy Mountains and abandoning plans for controlled culling is "madness" and "disaster" for the nation's natural heritage, says a leading professor.

Deputy NSW Premier John Barilaro has backflipped on the state government's proposed culling plan in Kosciuszko National Park, citing the cultural significance of the brumby.

"Wild brumbies have been roaming the Australian Alps for almost 200 years and are part of the cultural fabric and folklore of the high country," he said in a statement on Sunday.

Leading scientists from around Australia have long supported plans to cull the brumby population from 6000 to 600 over 20 years, arguing it's needed to protect the delicate Alpine environment.

Professor Don Driscoll, from Deakin University, says Sunday's decision will affect natural species, natural fauna and water supply, which could also affect the Snowy 2.0 scheme.