A large section of Connemara National Park has been declared off-limits to walkers because of erosion of the bog caused by trampling.
Dúchas, the Heritage Service, has erected signs around the park forbidding access to Diamond Hill, one of Connemara's best-known mountains, above the village of Letterfrack.
Dúchas now plans to erect a boardwalk up the mountain, but this will cost an estimated €1.27 million and take three years to put in place.
An environmental impact study will be carried out before work starts on the boardwalk.
The ascent of "the Diamond" is one of the most popular climbs in Connemara; an estimated 10,000 people try it each year.
However, the passage of thousands of heavily-shod feet over the terrain has caused significant damage to the fragile bog. The first stage is the creation of a track, but as this has become waterlogged and muddy, walkers have moved out onto the surrounding untrampled areas, thus extending the damage.
While walkers' and local tourism groups have welcomed the attempts to protect the mountain ecosystem, there are concerns that a wooden walkway could attract even greater numbers to the mountain, as well as being visually unattractive.
The decision to close off the Diamond has been welcomed by the Irish Peatland Conservation Council. "If nothing was done, you'd end up with a black slop of bog and no-one would be able to climb the mountain," said Dr Fiona MacGowan who has studied erosion of the mountain.
Dr MacGowan's research shows that the main plants to suffer from erosion are the ground-hugging mosses and liverworts. With only minimal trampling, 20 peatland species disappear, including the scented bog myrtle and the carnivorous butterwort. Other plants such as ling heather, bog cotton and purple moorgrass survive for a while, but eventually go into decline if trampling continues.
"It comes down to proper management and striking a balance between the needs of the environment and desires of walkers. If people can be kept to one or two paths, even if there is a problem with visual intrusiveness, this can play a major role in protecting the bog," said Dr MacGowan.
The Mountaineering Council of Ireland says it has "no objection" to the planned boardwalk. Its chairman, Mr Peter O'Neill, said: "We would be concerned, however, with the proposed timescale. Three years is a long time to keep the mountain closed, if that is what is intended."
Connemara National Park, which is one of six in the State, was opened in 1980, when it attracted 9,000 visitors. Since then, the annual number of visitors has risen to 75,000, although most do not venture further than the visitor centre and surrounding nature trails.
These are not affected by the current restrictions. The potential for further growth is considerable, according to Mr Pádraig Lyden, a member of the local liaison committee of the park.
Nearby Kylemore Abbey attracts 180,000 visitors annually, he pointed out.
The park has an area of almost 3,000 acres, stretching from sea level at Letterfrack to the peak of four of the 12 Bens. While many of the popular walks on the Bens are not affected by the ban, access to the higher peaks is no longer possible through the national park.
Erosion is also a problem in parts of the Wicklow and Kerry mountains.
Railway sleepers covered with chicken-wire have been put in position along parts of the Wicklow Way to minimise the damage caused by walkers. However, the problems associated with erosion continue to worsen as the numbers using the mountains increase.
