Why the ash tree could disappear from the Irish landscape

Analysis: ash dieback disease is causing serious damage to one of the most beloved tree species in Ireland

By Marion McGarry and Sean Garvey, GMIT

One of our most beloved tree species in Ireland, the ash, is under grave threat of elimination due to a fungal parasite known as ash dieback. This is a serious disease affecting ash trees and is caused by the fungal pathogen Hymenoscyphus fraxineus (previously known as Chalara fraxinea), Fraxinus excelsior being the scientific name for native ash.

Ash - in Irish fuinseóg - is the most abundant tree in Irish hedgerows. It's significant for farmers but hugely important for biodiversity and providing habitats for wildlife. The tree is widely distributed across the island and is a woodland species. Hedgerows the length and breadth of the country are characterised by their tall canopies, the last to come into leaf in spring and the first to lose their leaves in autumn.

As one of our very few native trees, there are almost one thousand associated species that use it in some way or other. Insects and mammals use ash as a food source; some birds use it as a place to hunt, nest and breed and many bryophytes and lichens use the ash as a habitat in which to live. While most of these associated species can use other trees for the same purpose as ash, it is the sole foodplant for a number of species of insects, lichens and mosses.

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From RTÉ Lyric FM's Naturfile, Anja Murry looks at Ireland's rich history of native Ash trees

It is also a tree species that is important in terms of culture and folklore. Trees were once abundant and significant to Irish identity, and many remain symbolic in our culture. Some are evidence of the last remains of ancient tree worship when sacred trees were found adjacent to a royal residences, or marked important places. Three of the legendary five great trees which guarded the provinces of Ireland were ash.

It was once thought that if a holy well dried up, its power went into the tree that stood closest, usually an ash. Ash trees were considered under the old Brehon Laws to be of the high-ranking 'noble' classification and severe fines could be issued for damaging or cutting such trees without the landowner's permission. The letter nion in the Ogham alphabet is named for ash, and trees such as ash featured in early Irish poetry. Ash gave many Irish townlands and landscapes their names.

Ash is fast growing and makes excellent firewood. It gives a very useful timber with a fiery grain which makes it popular for furniture and other products to this day. Its flexibility and superior lateral strength led to its notable association with the traditional manufacture of hurleys, which led to ‘the clash of the ash’ nickname for the game. However, much ash for hurley production has had to be imported to Ireland in recent years.

From RTÉ Radio 1's Drivetime, John Cooke talks to hurley makers about the crisis around a disease that affects ash trees

While ash is one of our most culturally significant and common native species, it is currently under threat of disappearance from ash dieback. The disease has been in the country for the past decade, but its impact only really became noticeable last summer through the distressed looking leafless extremities of ash trees poking up from hedgerows across the country. Most did not come into full leaf on all their branches and the tips of the trees were instead leafless and skeletal, offering evidence of their gradual zombification.

Tree cover in Ireland has been on a slow rise since the beginning of the 20th century when it stood at only 1% and ash woods have played their part in this - at least until the arrival of the disease. By losing ash from the landscape, we face negative changes to ecosystems and biodiversity levels. The threat of ash dieback is akin to the demise of elms caused by Dutch elm disease. It is a very rare sight nowadays to see an elm grove, with only a few sporadic individuals left in the landscape. Ash trees unfortunately may face the same fate.

Ash dieback first appeared in Ireland in 2012 and is believed to have originated in eastern Asia. Its effect here is mirroring high mortality rates seen in other European countries. The disease causes the tree crown to die back and root rot from secondary infections caused by other pathogens are common due to stress and low immunity. Over a number of years, this usually leads to tree death. Young trees seem to be more susceptible than older ones and usually die quickly.

From RTÉ Radio 1's Drivetime, Mike McCartney reports on the ash dieback tree disease

The disease is most often spread by fungal spores carried in the air and landing on a new host or already infected tree during the summer months. The fungus overwinters in infected leaf litter on the ground and the cycle continues when spores are released from the fungal fruiting bodies. These spores are microscopic in size and easily carried by the wind for up to several kilometres.

Research has shown that woodlands with high genetic and age diversity are more generally resistant to disease, yet many of our ash plantations in Ireland exist as an even aged monocrop. We can mitigate new diseases to Ireland like ash dieback causing so much devastation in the future by managing our woodlands to favour diverse species of uneven aged trees. A close-to-nature approach could be one way to increase resilience.

We have seen anecdotal evidence in other European countries that some trees and woodlands are now showing some sign of slowly bouncing back

All may not be lost though, as some ash trees have shown some natural resistance. Organisations like Teagasc continue to carry out research into the disease, mitigation management and the building of a gene bank where ash trees can hopefully be returned to the Irish landscape, bred from trees that show genetic resistance.

We have seen anecdotal evidence in other European countries that some trees and woodlands, which had been very suppressed by the disease, are now showing some sign of slowly bouncing back. While mortality rates caused by the disease across Europe are high, it has not been found to be 100% in any location and this includes areas where the disease was first detected over 20 years ago. This gives us hope that ash populations here and in Europe could recover, albeit over a long period of time. Hopefully this recovery will happen before the next big threat to our beautiful native ash arrives – the emerald ash borer beetle.

Dr Marion McGarry is an art historian, author, independent researcher and lecturer at GMIT. Sean Garvey is a lecturer in furniture design at GMIT Letterfrack.

The views expressed here are those of the author and do not represent or reflect the views of RTÉ

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