IT’S been a sad week for our woodlands.
More cases of the devastating ashdie back disease have been now been confirmed in infected trees in the Republic, Scotland and England, including two Wildlife Trust nature reserves in Norfolk and Suffolk. If this dreaded fungus spreads into Northern Ireland, it could have a disastrous impact on our natural environment and our local biodiversity.
The fungus Chalara fraxinea infects 60-90 per cent of the trees in its path, causing leaf loss, bark lesions and crown dieback, and can ultimately lead to tree death. Experience indicates that it kills young ash trees very quickly, while older trees tend to resist it for some time, until prolonged exposure causes them to succumb as well.
The infection biology of the disease is not fully understood. Evidence suggests that the majority of infections first occur on ash leaves, indicating that the disease’s main form of spread is via wind dispersal. This adds weight to the ideas that the most probable cause of the outbreak was spores carried on the wind from Europe, where the disease has already caused widespread damage.
Ash is one of our most common native trees and makes up around 30 per cent of all our woodland cover and the thousands of miles of hedgerows which knit our landscape together. It is a vital component of woodland ecosystems supporting many plants and animals, from iconic woodland flowers such as bluebells to hole-nesting birds such as barn owls, to hundreds of invertebrates and lichens.
Reports about 100,000 infected ash trees in nurseries being destroyed in a bid to prevent the disease spreading has led to speculation about the destruction of ash throughout our countryside. If the disease is widespread, this approach may be ineffective and could be counter-productive in the wider environment.
Our wildlife is already under huge pressure and this issue emphasises the need to do all we can to ensure that nature is more resilient in the future. Any response to deal with this disease must take a precautionary and science-led approach. Dutch elm disease in the 1970s for example, illustrated that hasty reactions in the early stages of a crisis can result in the ‘cure’ being worse than the cause.
Ash trees are genetically diverse, unlike the English elms, so it could be that some will have a level of resistance to ash die back. If we destroy all those considered infected, or that are near a source of infection, then a naturally resistant population may never emerge. Reducing our ashes literally to ashes could devastate the environment and still have no effect on the disease.
As Northern Ireland is one of the least wooded areas in Europe, we will be keeping a very close eye on this issue and will be lobbying our government not to be drawn into knee-jerk and potentially damaging solutions if the disease takes hold here, which we now fear is only a matter of time.
We would ask everyone to be vigilant and to report potential sightings of infected trees to the Department of Agriculture and Rural Development in the hope that the ecological impacts can be minimised - tel: 0300 200 7847 or email firstname.lastname@example.org.
For further information on the disease, visit our website www.ulsterwildlifetrust.org
Nature Reserves Manager
Ulster Wildlife Trust