Ecological impacts of ash dieback and mitigation methods

Ash is a widespread species which makes a substantial contribution to many landscapes. Ash trees are affected by ash dieback, a disease caused by a fungus. It is clear from the European experience of the disease that a significant number of ash trees could be lost from woodlands in the UK over the course of perhaps the next 20–30 years. The ecological implications of the loss of ash trees encompass the biodiversity supported by the tree itself, as well as the ecosystem functions the species provides. This Research Note summarises recent research on the ecological value of ash, on tree and shrub species as alternatives to ash, and on the interpretation of this information for woodland management. The ground flora community associated with ash woodland is distinct and diverse and the species exerts a significant effect on habitat composition. Other tree and shrub species which occur in UK broadleaved woodlands, or are suitable for planting there, support many ash-associated species such as lichens, insects and fungi. However, the alternative species that support most ash-associated species do not replicate the ecosystem functions provided by ash. Various options are available for broadleaved woodland management, from relying on natural succession to planting specific species or mixtures of species to meet objectives of either ash-associated species conservation or ecosystem functioning and habitat maintenance. Encouraging the establishment of alternative tree and shrub species that are ecologically similar to ash may offer options to mitigate against the ecological implications of ash loss.