Medieval and colonial demesnes uncovered

Palimpsest is a word I like to dust off now and then. It dates from the days when parchment might be used several times, the older, rubbed-out writing a ghostly presence behind the new.

It carries a sense of time's texture, of successive human purposes. As leaves drift and bracken crumples, as the older bones of the landscape begin to show, "palimpsest" seems quite appropriate for a project under way in the British Library In London.

There, the 19th Century maps of the Ordnance Survey of Ireland, originally made for taxation purposes, offer the only complete record of the boundaries of a lost Ireland. They are the maps which, framed under glass on the walls of old Irish country houses and angling hotels, evoke stark journeys through sepia-hatched valleys between the little green blobs of Big House demesnes. Now, overlaid by modern maps, in a computer enterprise centred on the British Library, they are helping to construct a view of Ireland in which the old parks and gardens are etched behind the fields, roads and fences of our largely remade countryside.

The initiative comes from the National Inventory of Architectural Heritage, a unit of the former Duchas now within the Department of the Environment, Heritage and Local Government. Worried about today's new pressures from development, it has commissioned a UK landscape consultancy (Richards, Moorehead & Laing of Ruthin, North Wales) to find Ireland's lost parks and gardens and weave them into a database - partly for the record, but also to open new options for conservation.

Anyone who has wandered farming backlands and forestry plantations in search of the past knows what extraordinary conjunctions one can still come across: vast porticoed ruins marooned in mazes of barbed wire; family mauseoleums framed in Gothic conifers; stately terraces embalmed in moss. It makes it easier to imagine that there might, indeed, be treasures worth conserving, and even restoring, among remains of the old man-made landscapes .

So far, the project's "paper" search has found more than 3,100 "historically important man-made landscapes" in 13 counties - some 800 in Co Cork alone. When it completes its survey early next year, the total is expected have reached 6,000. It will draw together the existing work of many local historians and groups, with a steering group of Irish garden and landscape experts.

Medieval and colonial demesnes once covered more than 5 per cent of Ireland, and by the 1830s and the first ordnance survey their walled parks stood out as leafy oases in an often bleak and treeless landscape. By this date, too, the formal avenues and gardens were giving way to a different relationship with nature - a romantic landscaping of rolling meadows dotted with clumps of oak and beech, with a lake to mirror the house and tree-lined glades furnished with temples and grottoes. It is hard to think that many such parklands have survived outside private ownership, or conversion to country club and golf course (though some farmers may, I suppose, be stacking silage in "Greek" pavilions).

Some of the estates overplanted with spruce forestry in the early decades of the State are now being cleansed to great effect. At Inistioge in Co Kilkenny, where Woodstock House was burned in 1922, the fine gardens,with their lofty avenues of monkey puzzle and noble fir, are under county council restoration.

At Brackloon Woods, near Westport in Co Mayo, clearance of the conifers has reclaimed a stand of trees of even greater merit - sessile oaks in direct descent from Ireland's ancient native woodland.

Scattered across Ireland are other, similar fragments, many in private hands, that have preserved a precious link with ancient ecosystems. The Native Woodland Scheme launched by the Forest Service in 2001 set out to conserve, restore and extend such woods with the aid of State grants - the best news for nature in years. But, as with other innovative projects endowed in more affluent times, the sap has been drying up just as real growth was getting under way.

Courses run by the Forest Service and the Woodlands of Ireland group have trained over 300 foresters, ecologists and landowners, and the scheme has brought agencies and NGOs together in a quite unprecedented way. But growing seedling oaks needs more certainty than the present cutbacks provide, and after Bertie's recent blithe put-down of "snails and swans", some nature-friendly reassurance would be welcome.

Meanwhile, it is good to see native trees and shrubs given their full whack alongside the conifers in a new book from COFORD, the National Council for Forest Research and Development. Definitive and handsome, A Guide to Forest Tree Species Selection and Silviculture in Ireland (30 Euro, plus p & p) is aimed particularly at the thousands of new forest-owners who have turned to trees in recent decades. The five authors all currently work for Coillte and their deep knowledge of Irish conditions should help to get the right trees planted in the right place, and in mixtures that make sense both to foresters and ecologists.