Compiled by Chris Reid, Emma Goldberg and Charlotte Lemmon. Includes advice on and for Environmental Stewardship and SSSI owners/occupiers
Advice for Natural England’s Land Management Advisors on ash dieback (Hymenoscyphus fraxineus) for Environmental Stewardship agreement holders and SSSI owners/occupiers
What is this guidance for?
There is information & advice about ash dieback on Forestry Commission’s (FC) website, at www.forestry.gov.uk/chalara. This note adds to the FC’s advice, particularly for woodlands and trees of high conservation importance.
Ash dieback disease is an air-borne fungal infection of ash trees that has potential to kill young trees and render older ash susceptible to fatal infections by pathogens like honey fungus. There appears to be very limited resistance to ash dieback across Europe. The spread of the disease across the country is inevitable. Our recommendations aim to slow the spread of the disease; improve woodlands’ resilience to disease; and ensure that ES agreements are not put at risk.
Ash is a widespread native tree species in England. It has a unique set of ecological characteristics, and there is no obvious alternative tree species which will readily replace its ecological functions. Other native trees share some of these characteristics, and provide suitable habitat for some of the species of animals and plants that depend on ash.
Our advice to woodland and landscape managers on what to ‘do’ about ash dieback will therefore vary depending on the site’s features of interest and its ecological potential, as well as the owner’s objectives. Overall we are aiming to achieve resilient woodlands and tree populations, with a diverse structure and species composition. This will also involve reducing other sources of stress on these trees and woods, so they are better able to adapt to ash dieback. This will be a long-term process which will evolve as the disease progresses.
Identification of the disease
Land owners/managers who suspect they have ash dieback on their site should be directed to the FC website and reporting system to check symptoms: forestry chalara reporting and report them at forestry tree alert (including photos). They should then contact their NE adviser if the site is under ES agreement or is an SSSI, and they are convinced their trees have the disease.
Impact on Environmental Stewardship agreements
Payments made under ES for ash tree planting or restocking that has failed due to ash dieback will be allowed to continue using the Force majeure (‘exceptional circumstances’) rule. But agreement holders have to request for this rule to be applied to their agreement within 10 days of diagnosis of the disease. The request must include photographs of the affected trees and information on their number and location.
Defra are considering whether we can fund the removal and replacement of affected trees planted under ES agreements. This requires approval from Europe. The FC has set up a Woodland Improvement Grant for ash dieback to fund the removal and replacement of infected ash trees funded under EWGS since 2007.
Our advice to woodland owners and managers is not to undertake any work in haste. Advice from the continent is that, for mature trees and woodlands, felling infected trees, or even healthy ash trees before infection takes hold (“sanitation felling”), will not help control the spread of the disease.
We recommend drawing up a management strategy across the woodland/ estate which, over time, aims to:
o Diversify the tree and understorey species composition, favouring a mix of native* trees/ shrubs that provide appropriate alternatives to ash for the wood’s interest features (such as rarer flowering plants, lichens, invertebrates etc), and the owner’s objectives. Do this primarily through protecting natural regeneration and/ or by planting if necessary. *For non-SSSI semi-natural woods it may be acceptable to encourage/ plant a small proportion (<20%) of site-adapted naturalised species (like sycamore) or non-native trees, in line with FC advice on climate change resilience and the woodland managers objectives.
o Diversify the structure of the woodland so there is a mix of tree and shrub age and size classes present, and well-structured rides and glades. Recently-cut ash coppice and pollards will be very susceptible to death should they become infected by ash dieback – it is advisable to move away from these practices for ash. Losses of some ash may be inevitable, but veteran ash coppice stools could be ‘singled’ (this has not been tested).
o Reduce other sources of stress on the woodland especially browsing pressure caused by deer, livestock, rabbits etc; agricultural spray drift; and presence of invasive species, including some conifer regeneration.
o Consider opportunities to expand and/or link woodland blocks, using native species where possible, to increase their resilience.
Many woods will maintain their woodland interest if we can succeed in diversifying the native tree and shrub species present (see above), and/ or if we find disease-resistant ash.
If a site has ash dieback, it will not automatically go into unfavourable condition, but will go onto our threats register. Our standard target for tree disease is: “No rapid loss of native species due to unnatural factors (greater than 10% in a five year period)”. This will trigger a site to be switched into unfavourable condition, but if the land owner were already in discussion with Natural England about diversifying the tree and shrub species, and taking steps as set out in this guidance, the site condition may be classed as unfavourable recovering.
This means decisions on condition should follow this approach:
• If a woodland does NOT have ash dieback then there is NO impact on condition but, where its features are at risk then a Condition Threat and appropriate Action should be recorded. The Action may include establishment of a management strategy to diversify and reduce other stress factors.
• If ash dieback is present then either:
o If the loss of native species is less than 10% over a 5 year period, then there is NO impact on condition, but we try to manage it (and this must be recorded via an appropriate Condition Threat Action); OR
o If the loss of native species is greater than 10% over a 5 year period, then condition is UNFAVOURABLE and either:
• If appropriate management is in place to manage a shift in component species to re-establish the woodland structure, then if this is the only factor affecting condition then it is unfavourable recovering. A Condition Threat Action must be recorded to reflect the continuing need to manage the site; OR
• If appropriate management is not in place, then an unfavourable declining category is likely to be most appropriate if the impact of the disease is continuing to increase.
• In the future, if there is a permanent adverse effect that fundamentally alters the notified features of specific sites, then advice will need to be sought as to the way forward. However, staff should not focus on this activity now as we are a long way off this potential scenario.
Natural England is developing a monitoring programme to look at the impacts of ash dieback. If you find owners willing to be involved in monitoring programmes, we’d be interested in hearing from you.