Killarney National Park, Co Kerry, is the first Irish national park. It is managed by the National Parks and Wildlife Service (NPWS).
In 1982, Unesco awarded Killarney the status of a biosphere reserve, and included its cultural attractions, along with woodlands, lakes, parkland and gardens.
Mr Ryan said there is “real concern” among conservationists about the state of the 25,000-acre park, and particularly about the decline of the woodlands because of over-grazing by deer and ruminants and the invasive rhododendron.
The park will probably lose the designation, he said.
“There is real concern that we are losing what’s really precious,” said Mr Ryan, who worked in cycling tourism business in the Co Kerry town for more than a decade.
People on the ground know there is a real problem “and we’re not wining the battle”, Mr Ryan said.
The Irish Wildlife Trust were right, he told Radio Kerry. Killarney National Park is “a stunning resource for the whole country”.
Not being able to look after the Killarney park is symbolic, he said — if we can not look after Killarney, we can not win the bigger battles.
Rhododendron ponticum is the first priority and is now taking hold of the woodlands, killing the undergrowth, and threatening the future of the natural forest, Mr Ryan said.
Voluntary groups such as Groundwork have been fighting rhododendron in the park since the 1980s, but there was a dispute between the NPWS and those organisations.
The Irish Wildlife Trust (IWT) wrote to Paris-based Unesco last week saying Killarney has failed to maintain standards of conservation and protection and it should be forced to reapply for the coveted status which the park uses to promote itself.
Killarney has not lived up to its status, the IWT says in a formal complaint.
The trust, established in 1979, which is concerned with habitats as well as wildlife, told Unesco it has had concerns for a number of years about “(mis)management” of the park.