A conservation plan for the main wetland area within Limerick city's boundaries recommends the development of a sluice system as a protection against pollution at the docks.
The Westfields area is part of the Lower River Shannon region, which is proposed as a special area of conservation. But it is under threat from Limerick Docks in the Shannon, just a few hundred yards south of the wetland.
"This stretch of the river has a high risk of pollution incidents," the consultants' study notes. It recommends that an official should be employed to manage the site and provide an educational service.
"It is one of the richest sites we have and it is well worth preserving," said Mr Tom Tarpey of Birdwatch Ireland, who contributed to the study. "Green space is under pressure in general. This is a green oasis in the middle of a fairly well developed area."
He said wetland areas were under threat everywhere. "Every time you wipe out a wetland, you are reducing the numbers of birds, and this is a problem in Ireland as well as the developed world. Wetlands are disappearing bit by bit. In the interests of maintaining biodiversity globally, we have to preserve our wetlands."
The 26-acre Westfields area, adjacent to the Shannon and divided by the N18 road to Galway, is described as "one of the finest medium-sized urban nature reserves in Ireland". With housing estates bounding one side, it is a popular area for walkers.
The plan, drawn up by Natura Environmental Consultants, states that the 65-acre area is "of special note for its wintering population of water birds", and is part of the Shannon/Fergus system, which has the highest concentration of wintering birds in the State.
Mr Tarpey noted there were 25 wildfowl species at Westfields and a study by Liam Lysaght found 31 species of breeding birds.
"It is always a good place to see a few scarce species. Shoveler and gadwall are relatively scarce ducks in Ireland and Westfields is a good place to find them. It is a good place to go all year around. There is always something there. It attracts a lot of warblers which come to Ireland, willow and sedge warblers in particular," Mr Tarpey said.
According to the consultants, the area "is one of a number of surviving fragments of a once extensive wetland complex that existed around the estuary of the Shannon at Limerick", which should be developed with a series of wooden boardwalks, interpretative display panels and a nature trail.
Mr Oliver O'Loughlin, the corporation's director of service for planning and the environment, said that although the natural development of a wetland is to change to dry land, the aim was to preserve Westfields. The plan had been approved by the strategic policy committee involved and a period of consultation would follow. "The next phase is to quantify it, to come up with an operation plan in consultation with the Westfields voluntary group."
The development of a sluice system would prevent saline intrusion and prevent the entry of pollutants from the river. It would also prevent sewage from entering the wetland.
The Westfields Management Plan also notes the presence of Japanese knotweed, an "invasive species" which should be removed entirely. "It could invade the entire wetland at the expense of native plant communities."
Other remedial measures include the removal of reed, bulrush and scrub from certain sections "to reverse the natural succession from open water to dry land", the excavation of sediment to create a basin with a variety of depths and ecological conditions, and the planting of semi-mature native species such as alder and ash.
Mr O'Loughlin said the operational plan would be developed in conjunction with Duchas, the Heritage Service. "We would be looking at this in the context of an overall management plan for all the wetlands."
The consultants note the presence of the zebra mussel, a "cause for concern as this exotic species can invade waterways and exclude native fauna". Populations of mallard, teal and coot are in decline, possibly due to the decrease in the area of open water at the wetland.