TRANQUIL SETTING Lough Carra at sunset, from the Moorehall shore. Pic: Lynda Huxley
Stunning Lough Carra, a unique home to an abundance of natural treasures, is under threat
The West of Ireland is renowned for the quantity and quality of its inland waters. Rivers, streams, loughs, ponds and turloughs are scattered across the landscape like jewels. Among these aquatic gems, there is one which is truly unique: County Mayo’s Lough Carra.
This lough is the uppermost in the Carra/Mask/Corrib system that forms a major part of the Great Western Lakes of Ireland and that drains a huge catchment in the two counties of Mayo and Galway.
Although relatively small in comparison with Loughs Mask and Corrib, Lough Carra’s 1,500 hectares have the distinction of being, at least for the moment perhaps, the best example of a shallow, marl lake in western Europe. As such, it is of enormous ecological and conservation importance. Indeed, it is for that reason that the lough was designated as an SAC under the European Habitats Directive.
But it is not just the aquatic environment that is of great value, as the lakeshore holds some of the richest terrestrial habitats in the country.
Situated on the carboniferous limestone that is, in effect, an outlier of The Burren, the lakeshore has a mixture of limestone pavement, grassland, fen, marsh, reed swamp, scrub and woodland. These habitats harbour a fantastic variety of wildlife, including over 400 species of higher plants, 25 species of butterfly, 14 species of dragonfly and 20 of Ireland’s 26 orchid species.
Indeed, naturalist, writer and librarian Robert Lloyd Praeger was clearly impressed with the orchid display and mentioned that he had never seen Marsh Helleborine in such profusion. I believe that the Carra lakeshore is probably the richest orchid site in Ireland. The presence of dense-flowered orchid and spring gentian demonstrate the biogeographical link to the Burren.
A full 140 bird species have been recorded at the lough, and at least 83 of these have bred there. There is an autumn/winter starling roost in the reed beds with up to 60,000 birds, but even more important is the swallow roost in August, when as many as 30,000 come together each night in the reed beds or bulrushes.
Then and now
We are lucky that Carra has been the object of much investigation over many decades. Praeger and ‘Robin’ Ruttledge both spent time exploring its habitats (the latter lived on the lakeshore for many years) and, in the 1960s and 1970s, a team led by Brian Stronach carried out intensive studies of the wildfowl.
Their work provided the baseline against which we can measure current populations. Not with optimistic results, I’m afraid, as many duck populations have crashed catastrophically.
In particular, mallard, tufted duck and red-breasted merganser have all suffered declines in excess of 90 percent. Although hard evidence is sparse, it seems likely that the arrival of American mink, coupled with increased hooded crow numbers and changes to both breeding and wintering habitats are to blame.
Similar declines have occurred in the breeding waders, especially lapwings and ringed plover. A few redshank and common sandpiper pairs hang on, but predator numbers allied to overgrazing continue to be of concern.
With just about all the protective legal designations possible, one would have thought that the aquatic environment for which the lough is so important would be well looked after, but, sadly, this is far from true.
Dramatic increases in conversion of semi-natural habitats into improved agricultural grassland (25 percent of the land area in the catchment in 30 years) with concomitant increases in livestock numbers and the application of chemical fertiliser and slurry have resulted, not unexpectedly, in the nutrient enrichment of the lough.
Between 1970 and 2003, cattle numbers rose by 42 percent, sheep by 136 percent. Slurry application by 300 percent and chemical fertiliser use by 90 percent. It is not at all surprising that nutrient enrichment has become a serious problem.The process of eutrophication—when a body of water becomes overly enriched with minerals and nutrients that induce excessive growth of plants and algae, frequently due to run-off from the land—is evident in many aspects of the aquatic ecology, but has been masked to some extent by the very nature of the lough.
The thick layer of marl on the lakebed has the ability to soak up nutrients, especially phosphates and thus act as a ‘buffer’, preventing the water from rapidly becoming ‘pea soup’. However, once the marl is saturated with phosphates, further inputs are likely to produce a more dramatic and long-lasting change in the ecosystem.
The evidence collected by a team from Trinity College Dublin suggests that this point has been reached, or is at least very close, which is perhaps why they refer to it as an ‘ecological time-bomb’.
More recently, Charophyte expert Cilian Roden has surveyed the aquatic macrophytes and reports worrying changes, including loss of water clarity and the spread of at least one invasive alien species. His work led to the National Parks and Wildlife Service recognising that Carra’s ecological status is unfavourable and inadequate and that future prospects are bad and declining.
Let’s take action
Lough Carra does retain much of its wonderful biodiversity and ecological value, although gradual and continuing degradation of the aquatic environment and terrestrial habitats are cause for considerable concern.
We have the legal and administrative mechanisms to arrest and reverse the decline and must hope that the relevant authorities will take the necessary action.
Now there is a local community driven initiative which we hope will assist in persuading the various government agencies to take action: a Lough Carra Catchment Association has been formed, with the support of the Water Communities Officer, Mick Kane.
The association’s aims will be to promote the restoration, protection and conservation of the ecological integrity of Lough Carra and its lakeshore habitats.
The next meeting is at the Village Inn in Partry at 7.30pm on Wednesday, April 18. Anyone with an interest in the Lough is welcome to attend and take part.
This article is an updated version of a piece that first appeared in the autumn 2015 edition of Irish Wildlife Trust’s magazine, ‘Irish Wildlife’.
Huxleys to give talk on Lough Carra
Lynda and Chris Huxley will give a lecture on Lough Carra’s natural treasures on Tuesday next, April 17, at the Westport Coast Hotel.
The talk, which starts at 8pm, is hosted by Westport Civic Trust.
The Huxleys have been monitoring the changes in Lough Carra for almost 20 years. Chris is a retired ecologist and conservationist and Lynda an administrator and semi-professional photographer, although their interest in the Lough has extended well beyond these areas.
In 2015, they published their book Lough Carra, which covers a wide range of topics, including archaeology, geology, history, angling and wildlife.
Details of their work, undertaken with the voluntary assistance of Mary Robert, a GMIT graduate, can be found on www.loughcarra.org.
No booking is required for this lecture, and the entry fee for non-members of Westport Civic Trust is €5 each. More details may be had from Pip Murphy on 087 2663423.
Praeger and the lake
In ‘On the Botany of Lough Carra’, published in The Irish Naturalist in September 1906, Robert Lloyd Praeger discusses one trip to the enchanting lake: “Towards the end of last July my wife and I spent four days at Lough Carra. By the kindness of Mr Stanhope Kenny, of Ballinrobe, we not only found comfortable quarters close to the lake in the house of Mr PJ Loughlin, but had a boat at our disposal, which was an invaluable aid to botanical work. Three days were spent on the water, visiting the islands, points, and bays, while on the fourth we cycled round the lake, to gain some idea of the flora of the adjoining country.”
Commenting on Lough Carra’s unusually coloured crystal-clear waters—a beguiling consequence of the lake’s lime-rich marl bed—he also wrote: “Lough Carra has long been famous for the wonderful colour of its water, which is a pale pellucid green. This results partly from the purity of the water itself, but mainly from the extraordinary limy incrustation which covers the whole bottom.”