Position statement on ash dieback

Summary

The future of ash woodlands is threatened by ash dieback; a disease often fatal to ash trees that causes trees to slowly die, drop limbs, collapse or fall. Ash is estimated to account for more than 10% of the canopy in 90% of woodlands in Gloucestershire and in some cases forms 80-100% of the canopy.

Ash is present in most of Gloucestershire Wildlife Trust’s wooded nature reserves, but is particularly prevalent in Lower Woods, Siccaridge Wood, Midger Wood and Snows Farm, and dieback has been recorded in all these reserves. At present there is no way to eradicate the disease and there is little that can be done to prevent its spread.

In places where infected trees grow beside roads, footpaths and visitor infrastructure, they are likely to pose a threat to public safety and will be removed for the safety of site users and to help control the spread of the disease. In these cases, ecological surveys are important to check for the presence of protected species such as badgers and dormice, enabling the appropriate mitigation to be undertaken.

Gloucestershire Wildlife Trust will be doing as much as possible to tackle the disease, including: 

• Monitoring infected trees
• Felling infected trees that could be dangerous to visitors
• Monitoring and identifying trees that seem to be resistant to the disease, and trying to encourage natural regeneration from them
• Where appropriate, allow deadwood to remain and new open habitats to be created within woodlands, as ash trees die or are felled
• Continue to look at potential tree species that could be a suitable replacement for ash, and introduce them where needed

Statement detail

Ash dieback is a fungal disease affecting ash trees, caused by the fungus (Hymenoscyphus fraxineus). It was first discovered here in 2012 and the disease is now present in all counties of England. Experience in Europe suggests that the majority of ash trees infected with the disease will decline and die over the next 10–15 years. 

There is no cure for ash dieback, but some trees are less susceptible to the disease. Investigating this natural resistance could be the best way to secure the future of the UK's ash trees.

Ash is one of the most common types of tree in the UK and an important tree in woodlands, open habitat and hedgerows and is a frequent early coloniser of open land. Ash allows a significant amount of light to reach the woodland floor, thus facilitating a rich ground flora. Ash dieback has huge implications for wildlife with over 1,000 species relying on ash trees as core habitat and 50% of obligate ash species at risk of extinction within 50-100 years. A smaller number of species associated with deadwood habitats may thrive for a short period in the conditions created by ash dieback.

Ash dieback will have a significant impact in Gloucestershire. To date, the disease has been recorded in 84% of the 10 km grid squares which wholly or in part cover Gloucestershire. This is an increase of 63% since 2016, so it is reasonable to assume that ash dieback will soon be ubiquitous across the county. 

Ash has considerable genetic variability and research is underway to identify resistant clones. There is no reliable estimate as to the prevalence of resistance within ash populations, but it is thought that resistance development should respond well to natural selection and selective breeding. Identifying resistant trees is a major strand of research and the national strategy to address the disease, however, this solution will not be in place before a considerable proportion of ash trees have been lost.