The Green Mantle

For a visitor the most memorable aspect of the Irish landscape is likely to be the luxuriance and variety of its plant life. Tree growth is almost entirely inhibited over a broad belt along the Atlantic seaboard: blasted hawthorn trees seem to lean uniformly inland, the salt winds trimming their western sides. Some sheltered sites, such as Connemara's lake islets, hidden in depressions, and the wizened stands of oakwood behind Croagh Patrick and Old Head, hold the few remnants of native wood in this great expanse of bare ground. In the better climatic conditions of the past these parts were densely covered by coniferous forest, and cutaway bogs often expose great numbers of in situ stumps, which grew any thing up to 7000 years ago, rooted in the soil beneath.

The oakwoods of Killarney around Lough Leane, those in Donegal by Lough Easke, and the woods west of Lough Conn in Mayo are examples of the deciduous forest which represents the natural vegetation of Ireland's lowlands. The sheltered valleys of east Wicklow: Clare, Glendalough and Glen of the Downs, are others. Such woods have the characteristic ground flora which marks centuries-old, primary forests. Plants such as bluebell, wood sorrel and wood anemone are suited to this habitat because they flower before the leaf canopy has developed and so produce a wealth of colour in springtime. Around them, too, are still scattered some of the economically unattractive tree species, such as holly and crab apple which remain as outliers of woodland in former times. Many place-names, such as Derry, Ros (as in Rosnaree), and others, reflect the once-extensive spread of this great forest, and one notes that these relate to the better-drained parts of the lowlands (marsh and bog inhibited its growth), and to sheltered valleys, for the exposed uplands seem to have been devoid of trees.
But the famous woods of Medieval times: the Dufrey in Wexford and the Royal Forest of Glencree near Dublin, have long gone, and everything that remains has been modified a great deal by human interference. Artificial grassland now dominates this natural setting and such common trees as ash, hawthorn, blackthorn and cherry are seldom found except where planted in hedgerows, where they mingle with such imports as horse chestnut, beech and poplar. In secondary woodland the more vigorous nettles, brambles and bracken tend to oust more colourful primary herbs. Some distinctive facets of the forest assemblage remain very localised, such as the hazel thickets on drained limey areas of the lowlands, e.g. the esker ridges near Tullamore and Tyrellspass in the midlands, and the groves of birch and rowan in upland hollows, but there must be others which we can no longer adequately recreate. Wherever Carboniferous Limestone rises sufficiently high in the topography to be free-draining and clear of glacial deposits, it forms a spectacular, naked-rock landscape with a quite unusual flora. The limestone plateau of the Burren in north Clare, roughly 120 square miles in area, is the most important cool-temperate limestone region in Europe, and there are smaller, less emphatic occurrences in the table mountains of Sligo, Leitrim and Roscommon as well as around Lough Gur in Limerick. The density of prehistoric settlement in such areas is often impressive and certainly the elaborate ancient field systems attached to many of the Clare cashels would be quite out of place in today's barren environment. In fact, it seems that in Iron Age times and earlier, the Burren was sufficiently clothed in soil to support vigorous agriculture.

Today, virtually without cover, it carries a rich and varied assemblage of plants, tucked away in clefts in its rocky platforms. and in small grassy patches, whose blossoms produce a wonderful display throughout the warmer parts of the year. Distinctive lime-loving plants such as the blue spring gentian, bloody cranesbill and mossy saxifrage are associated in places with a range of orchids, Mountain avens, of arctic-alpine provenance, mingle with southern European forms such as the delicate maidenhair fern, and the natural hazel thickets here are the Irish stronghold of the rare pine-marten.

The low marshy country which flanks many of our major rivers inland is subject to seasonal flooding and is characterised by lush water meadows (or callows). The Shannon, rated to be the longest river in Europe which remains unpolluted, has much outstanding callows environment in its middle reaches below Athlone. It is a rich grassland with a wealth of colourful flowers: the common buttercup, dandelion, ox-eye, sorrel, and the more distinctive meadowsweet and marsh cinquefoil. Bird migrants, the once-common corncrake, for example manage to hold their own.

Dune belts and salt-marsh are special coastal environments in which grasses or related plants play a major role in stabilising the new sedimentary accumulations. They are, in fact, part of the syndrome connected with drowned coastlines. The dune belts of Dundrum Bay in Co. Down and Bull Island in Dublin Bay will be familiar to many. At the seaward side of the dunes creeping grasses, whose stolons or rhizomes can spread along the loose sand and form a stable environment for plants, are typical. Nearest to the tide mark salt-tolerant sea couchgrass is usually the first prominent coloniser. Higher up, and out of reach of the sea water, marram grass takes over and the dunes may reach 150 feet in height. Behind this outer belt the sheltered leeway has varied grassland with mosses and a variety of flowering plants, maybe with clumps of alder, the home of larks and other small birds.
In brackish estuaries and muddy lagoons on the land ward side of sandbars salt-marsh develops to reclaim the evolving mud-flats which are the haunt of great flocks of wading birds: dunlins, oyster-catchers, curlews, to mention a few, as well as migratory ducks and geese. Again, the North Bull is an outstanding example, a nature reserve of international renown which exists literally within the limits of the capital city, and salt-marsh is also present in the other tidal inlets along the north Dublin coast. It is populated by halophytic, or salt-tolerant, plants and is covered for the major part at high tide. The succulent glasswort is the first coloniser on the mud flats to give a meadow type of vegetation but cordgrass, introduced to the Dublin marshes for reclamation purposes, now grows in conspicuous clumps as does sea lavender and sea plantain. Beyond high water limits rushes, sedges and grasses such as red fescue have taken over from the halophytes. Here too, but more typically on coastal cliffs, colonies of sea pinks locally give a profusion of colour in summer. Machair (machaire in Irish means 'low flat country') is a Scots Gaelic word from the Western Isles which refers to a special type of plant environment occurring on exposed Atlantic coasts both there and along the west coast of Ireland. It arises on the old beach deposits which may extend considerable distances inland and carry a great deal of calcareous material: comminuted shells, pin head skeletons of foraminifera, and coralline algae, the latter giving the misnomer 'coral strand' to some Connemara beaches. This is a grassland community of red fescue smooth meadow grass, sweet vernal grass, cocksfoot, Yorkshire fog, false oat with clovers and a colourful range of wild flowers: yellow flags in damp places, silverweed, harebell, speedwell and many others. The machaire is common land and so has not been modified by improvement procedures, and hay-making is late enough to allow its bird population of corncrakes and larks, with waders such as lapwing, plover and oyster-catcher, to raise their broods successfully. Any change in conditions, however is likely to eradicate this precarious environment.

Bogs, by far the most widespread type of natural vegetation remaining in Ireland, were formed around 9000 years ago, until recently occupying about one-sixth of the country. Shallow lake basins in the lowlands served as centres in which fen peat, made up of reeds, sedges and various water plants, started to form. As the lakes contracted and peat thickened, vegetation growing on the latter was blanketed off from the subsoil beneath and so became deprived of mineral constituents. Sphagnum moss, which can thrive virtually without inorganic materials, took over as a consequence and has produced the increasingly acid conditions which typify our modern bogs. The moss tussocks develop a hummocky surface interspersed with bog pools and support a very distinctive range of vegetation. Carniverous plants such as sundew and butterwort, get their nitrogen supplies from captured insects, while the shrubby tree growth, represented by clumps of bog myrtle, does so by producing root nodules in the manner of legumes. Dried-out surfaces are spread with heathers, the wide spreading and more restricted bell heather giving the delicate cover of purple and pink respectively to the bog lands in August.

On mountains such as the Wicklows one can see a range of plant associations which typify various parts of these boglands. A moss tundra with great spread mounds of Rhacomitrium is found on exposed summits where erosion is active. Wet bogland, in contrast to the drier heather moors, supports a vegetation of low, spiky deer grass, golden brown in autumn, associated with waving spreads of white-tasselled bog cotton. Marshy seepages on hill slopes are mostly dominated by rushes, while drier scree is often colonised by fraochans (bilberries). At a lower level rocky ground and thin soils are a blaze of golden furze: the common gorse up to about 1000 feet before June, and the smaller or western gorse higher up in the hill pastures after July. Bracken fern is a rapid coloniser of neglected hill grassland today. In the lowlands, the Pollardstown fell in county Kildare, a feeder of the Grand Canal, is an example of fen-type bogland, the southern borders of Lough Neagh another.

The wild areas are now almost everywhere under pressure from encroaching modern development: peat working, reclamation and land drainage, coastal exploitation for holiday use. It is a matter of the greatest concern to preserve even small pieces of these natural environments for the enlightenment of future generations.