When the wetlands are the last refuge for wildlife

Sunshine glints on frogspawn bunched like bubble-wrap in the pond, warms the creamy breast-feathers of the song-thrush on my windowsill, spotlights the first spring hare nudging through the rushes beyond - a week is a long time in meteorology.

But it will take more than a few days of high pressure and drying winds to make up for February fill-dyke. On farms all over Ireland, water still seeps around the rushes and sets dark reflections to alders and willows.

On land where rain has nowhere to run, these ragged wetlands, slowly drying out to scrub, become a sort of natural tithe on farmland, rough corners of refuge for wildlife even in the most intensive stretches of agriculture. When smaller, poorer farms are brought into REPS - the Rural Environment Protection Scheme - such wet, scrubby hectares are prized and protected.

Yet what do we know, really, of their value to nature and how they compare with the rest of the farm? Biologists are good at judging the ecological fabric of a whole landscape, but rarely study the biogeography of individual properties. And since wetlands, in particular, rarely stop at fences, should farms be "networked" in some way to conserve threatened habitats and species? In what could prove some crucial research for Ireland's eco-friendly farming, two scientists have teamed up to put a middle-sized farm under the microscope. It helped that one of them, Jervis Good, grew up on it and lives there still, an ecologist specially involved with the value of "wildlife corridors". His colleague in the project, Martin Speight, is the chief insect expert at Dúchas, the Heritage Service.

Their series of papers, just published*, makes a case study of the land at Glinny House Farm, a mixed livestock/arable farm in the rolling country around Riverstick in south Co Cork. For some 65 years the farm has been in the same nature-conscious family, but in following the general changes in farming it has already lost a good many species.

Changes in meadow management, common to the whole farm landscape, have dispossessed the corncrake, the skylark and the meadow pipit as breeding birds (and with the pipits' nests, the cuckoo). Introduction of winter cereals brought the persecution and loss of the rook. An end to outdoor poultry and cattle feeding drove the house sparrow away, and changes in farm buildings meant the barn owl disappeared.

The sale of a wet meadow, which was then drained and reclaimed, meant the loss of the small heath butterfly, and drainage and scrub clearance around a fen banished the water rail and snipe, together with several wetland flowers.

Today, following the European trend, the farm's productive land is used intensively, while its disused semi-natural wetland, with its alder thicket, is left largely to itself. In its contribution to the overall variety of species on the farm, it is not all that important: of 75 kinds of animals, birds, butterflies and dragonflies still breeding on the farm, it shelters only 11. The hedges, trees, stone walls and banks of the farm's "infrastructure" are just as valuable, supporting, for example, birds such as blackcap and treecreeper.

What makes the wetland special is its importance as a habitat for insects, notably the syrphids - the hoverflies - and sciomyzids, the little flies whose larvae kill snails. Both groups must be reckoned good for farming, as predators and pollinators and also as a food supply for dragonflies and birds.

One of the purposes of the case study was to decide what would happen to the farm's existing wildlife if the land use were changed in different ways.

One of these ways has been dramatically illustrated on the hillside across the valley, a mere kilometre away. Here, an area of 25 hectares (62 acres) has been converted recently from a group of hedged fields into one enormous field, for one intensive use: growing barley.

If Glinny House Farm were to bring the wet scrub and the "infrastructure" land into productive use, alongside its present grazing, silage and so on, it would lose about half its hoverfly species, says Speight. If it followed the example of the farm across the valley (and 40-hectare fields are no longer unknown in Ireland), its loss in syrphid fauna would be more than 80 per cent, from 73 species down to 12. Even those might not survive, if there was nowhere nearby to support them during the annual ploughing.

Jervis Good set out to predict the consequences for wildlife at Glinny House Farm of a whole range of more intensive uses and methods. Suppose, for example, the semi- natural area were "reclaimed" for a spruce plantation? That would lose the sedge warbler, long-tailed tit, reed bunting, willow warbler, frog, orange-tip and ringlet butterflies and common darter dragonfly, while gaining, perhaps, the long-eared owl and siskin as the trees mature.

Speight agrees that such conversion to conifers would result in a maximal loss of species from the farm. But with his great databank on syrphids (made happily available to science under the slogan "Syrph the Net") he offers a surprise. The disused land is probably uniquely responsible for more than 20 per cent of the farm's syrphid species. But its benign neglect, allowing the scrub to invade even further and dry up the wetland, will almost inevitably reduce that diversity by almost the same amount.

The greatest gains would come from keeping the boggy land in its present condition, or even reinstating the original acid fen.

But Speight admits the "air of unreality" of either option, which would mean active management without financial reward (in other words, "wildlife gardening"). Even under REPS, there's no money for this kind of work.

But even if it were available, the two scientists argue, would it be enough to maintain the habitats and species on one farm, while ignoring what was happening around it, particularly in a time of rising land values and drastic changes in use? To conserve the habitats in any one landscape and to help the dispersal and genetic flow of species, schemes like REPS will need to turn from treating farms in isolation and seek to set up chains of neighbours for complementary, eco-friendly management of land.

* The Bulletin of the Irish Biogeographical Society, No. 25, available from Dr Jim O'Connor, Natural History Museum, Merrion Street, Dublin 2

viney@anu.ie