At a deep fold in the Copper Coast, that 25km ancient stretch of the Waterford coastline between Tramore and Dungarvan formed 460 million years ago, the land yields to the sea, forming a sheltered deep inlet known as Stradbally Cove. Growing on the cliff edge is one of Ireland’s rarest native tree species: an aspen. Of all his field discoveries, Dr Daniel Buckley favours this specimen the most.
Buckley is a conservationist who spends his spare hours saving rare and threatened trees. He spent years searching for and testing the genetic diversity of black poplars across Ireland. More recently, he has focused his attention on the aspen, Populus tremula. This overlooked native tree rarely receives the attention and reverence accorded oak hazel, or hawthorn. Its ecological role, Buckley says, is “severely understudied”.
Aspen is more than a tree; it’s a host. In Scotland, it supports a specialised community of species that depend heavily upon it, such as the aspen hoverfly and the striking dark-bordered beauty moth. In Ireland, the aspen tree is home to the rare aspen leaf-mining moth, whose larvae tunnel through the leaves, leaving silvery trails. Where aspen declines, these species fade away, and so ensuring aspen’s future in Ireland is about more than saving a single species; it’s about safeguarding an ecological network.
Aspen is no recent arrival to Ireland. Pollen from a lake core on the Beara peninsula in Co Cork, and DNA analysis of lake sediments from Lough Feeagh in Mayo, both identify Populus from thousands of years ago, which confirms its long-standing presence as a native tree.
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Scattered across the country, it persists in small stands, but if you’re near one, your ears may pick it up before your eyes see it. Aspen’s rounded leaves have serrated edges and long, flexible stalks flattened on one side which enable the leaves to twist easily and strike each other even in the softest breezes, producing a rustling, shimmering murmur like falling rain. The sound brings the tree alive, almost as if it is chattering to itself.
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A publicly funded genetic study, led by Buckley, Colin Kelleher from the National Botanic Gardens and Clare forester Bernard Carey, and commissioned by the Department of Agriculture, aimed to answer a simple question: are the aspens growing around Ireland lonely remnants, or part of something bigger? The team sampled aspens from more than 20 counties and took 95 samples back to the lab for genetic analysis.
Aspen is dioecious: each tree is either male or female. If there are plenty of trees around, then the male will produce catkins packed with pollen, and the females will produce seeds. But when times get rough – if there aren’t enough trees near each other – aspen has a handy trick up its sleeve: it can clone itself by sending out underground roots from which new genetically identical shoots emerge. In the short term, it’s a brilliant survival strategy, but in the long term, on isolated islands such as Ireland, the danger is that the clones become, in effect, one organism and, as such, are locally vulnerable to pressures such as disease.
In this latest study, the DNA told a story the landscape could not: Irish aspen turned out not to be genetically impoverished relics, but rather members of a single, genetically interconnected population. From Antrim to Kerry, the trees share a broad genetic kinship. Over generations, Ireland’s wind, which carries pollen in spring and seeds in early summer, has done its work.
Even more hopeful is the balance between the sexes. If one sex dominates, reproduction falters. But across Ireland, the ratio is almost perfectly balanced. It is encouraging: overall diversity is intact, sex ratios are even, and no severe genetic bottlenecks are evident. All of this means that there’s a healthy range of raw biological material for viable seed production.
In the field, however, the aspen is under intense pressure from relentless deer overgrazing (aspen, high in protein, is delicious to herbivores). Root suckers are eaten before they can establish themselves; tender shoots are nipped off before they harden. It means that at a local level, there may be only single-sex stands. For the long-term success of aspen, it’s important to have as much genetic diversity as possible, with plenty of male and female trees near each other to encourage seed production.
Buckley and his team have begun to act. Taking inspiration from Scotland, where clone banks are used to protect aspen diversity, they’ve secured a space at the John F Kennedy Arboretum in Wexford to set up an Irish clone bank, which will act as a living genetic archive – a kind of insurance against their extinction.
From this, Buckley hopes to produce aspen saplings that can then be used in native woodland, agroforestry and commercial forestry schemes. Tall, straight aspens, which are favourable for forestry – they’re known as “plus trees” – have been discovered in Kerry, Kilkenny, Galway and Antrim. This all offers substantial grounds for hope regarding the future of aspen in Ireland.
