Grey squirrel's bite is worse for the bark

Another Life: One day in the summer of 1911, a wedding present from the Duke of Buckingham was ceremoniously opened on the lawn of Castle Forbes in Co Longford.

Up went the lid of the wicker basket and out leaped a dozen American grey squirrels, the very first in Ireland. To delighted applause, they scampered off into the woods.

Almost a century later, these rodents have colonised half the island and are still moving outwards at up to 3km a year. Their most serious threat has been to the native red squirrel. But, like the foreign deer launched in other Big House introductions, their potential for damage must also be reckoned with in the efforts to "releaf" Ireland.

In a year of rapid, sappy growth, thousands of young broadleafed trees throughout the eastern counties have lost their leading shoots or show the scars of bark-stripping by the squirrels, even to the point of total girdling of the trunk - potentially a fatal wound. Planted sycamore and beech are most at risk, but native willow, alder, elm and hazel are also vulnerable. Ash, birch and oak are occasionally attacked, but not in such a serious way.

In their native American woods, the greys do far less damage and are not considered a pest. According to one Irish forestry research report, bark-stripping may even be a kind of learned delinquency, initiated by juvenile squirrels in overcrowded woods. Browsing and bark-stripping deer damage a lot more trees than grey squirrels, but the American rodents do more harm to individual trees. At a time when private foresters and farmers are being urged to plant more broadleaves, the risk can be just one more reason for misgivings. "Are we just growing expensive food for deer and grey squirrels?" asked a delegate at a forestry conference this spring.

That certainly puts it too strongly. In some parts of southern England, where grey squirrels may be as many as eight per hectare, plantations of young beech are being dwarfed into scrub, and ash is taking over. So far, Irish densities are usually far lower - 2.5 per hectare in deciduous woodland, much less among conifers. Even at that level, control of their numbers can prove frustrating, if not futile, with trapping in spring still the best and safest option.

Damage from the greys matters most to foresters, who want trees to grow tall and straight, and has yet to be felt west of the Shannon (though the squirrels will eventually spread round at either end of the river).

Fallow deer, first introduced to Ireland by the Normans, are now in virtually every county. The bigger sika deer can become a serious pest in newly-planted woodland of any kind, browsing the leader shoots of young trees, and damaging older trees by scarring or stripping the bark.

At next week's big native woodlands conference in Galway, "managing the threat of mammals" is firmly on the agenda, together with sessions on threats from invasive trees and shrubs, such as rhododendron, and on the latest threat of invasion by a pathogen - the dreaded "sudden oak death" fungus of America's west coast - already imported to the UK and Netherlands. The risk of SOD makes it even more important that our native woods be built up with native stock.

There is a very positive aura, however, to Ireland's first major conference on the island's woods, helped along by ministerial commitment of 1m for new activity this year. The Forest Service's Native Woodland Scheme uses grants and training towards restoring and expanding what is left of native woodland and developing new broadleaf woods, especially along our river banks.

The conference is organised by Woodlands of Ireland, an NGO born at the time of the People's Millennium Forests project and supported by the Forest Service, the Heritage Council and the National Parks and Wildlife Service.

The NPWS has been assembling a national inventory of all the mossy shreds and patches of old oak woodland - many in private hands - that are potentially the nuclei of restoration. The owner of Charleville Wood in Co Offaly, home of the great "King Oak", will give the conference his view of the Native Woodland Scheme.

It was "on an island in a boggy lough in Co Offaly" that historical ecologist Oliver Rackham, of Cambridge University, found "an extraordinary wood of great ancient oaks, hung with ancient ivies (one ivy trunk is thicker than a fat man); it has the largest hazel and largest spindle-tree that I have ever seen".

He described this in his landmark book The History of the Countryside, and will give the keynote address to the conference, to be held next Wednesday to Friday at the Galway-Mayo Institute of Technology in Galway City.

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