The European Commission is taking the Republic to the European Court of Justice for failing to protect the State's largest special protection area and the habitat of a rare bird, the red grouse.
The Commission claimed the authorities here have not curbed overgrazing by sheep, and that this has caused "serious damage" to the 26-hectare Owenduff-Nephin Beg complex in Co Mayo.
The Commission cited the Republic's failure to preserve "other areas" of the red grouse's habitat, also by permitting sheep overgrazing. "The red grouse is particularly dependent on heather, which is one of the plants worst affected by overgrazing," the Commission says.
The application to the European Court of Justice against the Republic is for contravening the Wild Birds Directive on-special protection areas.
The Commission said that in relation to the Owenduff-Nephin Beg complex, evidence indicates that in certain parts "overgrazing is so severe that it has led to serious erosion of the fragile peat soils."
It added: "Apart from representing a threat to rare and endangered species such as the Greenland white-fronted goose and the golden plover, this represents an unsustainable form of land use and a destruction of the outstanding natural assets" where the EU has "financially helped the establishment of a national park which should provide substantial tourism benefits".
A spokeswoman for Duchas, the State heritage body, said it had not yet been informed by the European Commission about the decision and consequently could not comment.
The Commission admitted that since last year steps had been taken to reduce grazing in overgrazed areas by 30 per cent. But "other envisaged steps have not yet materialised." In particular, it said, the "authorities have not delivered any habitat management plans for areas affected by overgrazing, including the Owenduff-Nephin Beg complex."
It added: "Nor have they provided, by way of response, details of the common-age plans and other measures which need to be put in place in the complex."
Ms Margot Wallstrom, the EU Environment Commissioner, said, "If we are serious about the natural environment we must be ready not only to identify areas of high natural value, but also to give proper protection to those areas."
She added: "In the case of Ireland, the general need to tackle the devastating effects of sheep overgrazing seems to be accepted, and the Commission has agreed a financial package to help achieve this while safeguarding farmer incomes, but key actions to stabilise and redress the problem have still to be put into effect by the Irish authorities."