The Tree Council Ash Dieback Toolkit March 2025

ASH DIEBACK

AN ACTION PLAN TOOLKIT FOR LOCAL AUTHORITIES

Second Edition

Executive Summary An updated guide for ongoing challenges

Ash dieback is one of the most significant tree health issues affecting Britain’s treescapes. It is likely to result in the decline and loss of the majority of ash trees, threatening biodiversity, posing public safety risks, and altering our landscapes. It has been estimated that the total cost of the disease will be nearly £15 billion, including tree works, replacement of trees, and lost ecosystem services. A significant proportion of these costs will be felt by local authorities, who play a vital role in managing our treescapes.

It is crucial that the approach to dealing with ash dieback is proportionate, strategic and coordinated – this will give the best chance of an effective response and successful treescape recovery. In some cases, ash trees can be retained and safely managed, so the benefits they provide to nature and people are kept for longer. Research is showing that there is genetic variability in ash and so retaining healthier trees will make it more likely that the next generation of ash trees has greater levels of genetic resistance to ash dieback. To achieve the best results for ash trees and the wider treescape, local authorities and other organisations need access to the best evidence and information.

The Ash Dieback Action Plan Toolkit for England and Wales was first published in 2019 to support local authorities and others, providing essential information about the implications of ash dieback and the steps that can be taken to manage its impact. The toolkit has become the goto guide, used by local authorities across the country to prepare and implement action plans and secure budgets.

Severe progression of ash dieback through an ash woodland

Five years on from the toolkit’s original publication, there is now a valuable opportunity to learn from new research and benefit from practical experience gained by local authorities and other key organisations. As such, an updated version of the toolkit has been compiled, bringing together the latest evidence and sharing up-to-date case studies. It is designed to help local authorities to meet new challenges and work through different considerations as they shift from planning and awareness to action and recovery.

Working together

Ash dieback presents a huge challenge for many individuals and organisations who care for trees, but working together and sharing knowledge supports everyone in this journey. The development of the first and second editions toolkits was only possible through the generous contributions and support of many local authorities and other organisations, for which we are extremely grateful. The resulting document reflects the best available information at the time of writing, and we hope that it helps you manage ash dieback successfully in the years to come.

As ash dieback continues to impact trees around the country, sharing of knowledge and collaborative working is key.

How to use this updated toolkit

Local authorities are at various stages of managing ash dieback, so this toolkit has been designed to be used flexibly, according to each user’s needs. The first edition of the toolkit is still available for those who would like to refer to it.

If you are… How to use the toolkit

Learning about ash dieback

Developing an action plan

Head to Part 1 - this provides you with key information about the disease and its impacts. For your ease, information from the first edition toolkit has been brought across to this document and updated using recently published research.

If you are looking to develop or update an action plan the entire toolkit will be relevant, with Part 2 being particularly useful.

You should also refer to the first edition toolkit, which contains comprehensive guidance, tools, and templates for this stage.

Key highlights

- Introduction to ash dieback

- Updated distribution map

- Cost implications

- New research on genetic resistance and rates of decline

Updated toolkit

- Links to action plans published by a range of LAs

First edition toolkit

- How to make the case for an action plan

- Case studies with using lessons learnt

- How to assess and understand risks

- Guidance on survey techniques

- Support with communication strategies

Implementing an action plan

Looking towards recovery

If you are focussed on action, you may wish to head straight to Part 3 for a wealth of new guidance relevant to you, illustrated by a series of real-world examples.

However, do also check out Part 1 for the latest science if this interests you.

Every decision made throughout the response to ash dieback can affect recovery. Part 4 will help you approach this holistically, with useful tips and insights. From retaining ash where appropriate to replanting for resilience, there are steps that you can take to support recovery of healthy treescapes.

- How to carry out systematic monitoring

- Advice for minimising impacts on wildlife

- Detailed advice for large-scale ash works

- Insights into managing ash along roads and footpaths

- Important considerations for protecting tree workers

- A round-up of the latest scientific evidence

- Tips for leveraging funding

- An inspiring approach to recovery from the Saving Devon’s Treescapes initiative

Introduction

Ash dieback continues to be one of the most significant tree health issues affecting Britain’s treescapes. The invasive fungal disease, caused by Hymenoscyphus fraxineus, has continued to spread across the UK since it was first recognised here in 2012, with hugely detrimental effects on the native population of European ash (Fraxinus excelsior). Mortality rates are hard to determine due to the slow progress of the disease, but studies across Europe suggest it may be as high as 70% in woodlands and 85% in plantations (Coker et al 2019)1.

The total cost of ash dieback disease in the UK, accounting for loss of ecosystem services, cost of tree works and cost of replacement of ash has been estimated as nearly £15 billion (Hill et al 2019)2. Given the economic and ecological impacts of the disease, effective and sustainable management approaches are required. These must balance the health and safety risk of dead and diseased trees, with the necessity of retaining ash in our landscape where possible.

In 2019, The Tree Council produced the first Ash Dieback Action Plan Toolkit for local authorities. This toolkit aimed to provide a first response to ash dieback, as it became increasingly clear that this would be a major challenge for local authorities to address. At this point, most local authorities were in the early stages of their response (see Figure 1), so raising awareness and producing an effective strategy for dealing with ash dieback were the priorities. Given this situation, the toolkit focused on providing information about ash dieback as a disease, recognising it, and planning a response – with the aim of producing an action plan for dealing with ash dieback. Multiple local authorities have

1Coker et al (2019). Estimating mortality rates of European ash (Fraxinus excelsior) under the ash dieback (Hymenoscyphus fraxineus) epidemic. Plants People Planet

2Hill et al (2019). The £15 billion cost of ash dieback in Britain. Current Biology

Leaves of an ash tree infected with ash dieback

since made use of the toolkit to produce a formalised Ash Dieback Action Plan and many more have based their response around the guidance provided. A list of existing local authority plans is available on The Tree Council website.

ActionPlan

Mid rib of ash leaf showing the fruiting bodies of H. fraxineus. The fungus forms a hard sheath, preserving the rib of the leaf and preventing degradation, allowing the fungus to persist for longer in the leaf litter.

Close up of fungal fruiting bodies

Figure 1: Phases of a tree pest or disease response

Scale of the challenge for local authorities

In 2022, a survey of 42 local authorities was carried out by the Association for Public Service Excellence (APSE) to understand how they were dealing with ash dieback. The survey found that over 75% of respondents were expecting losses of between 60 and 95% of their ash trees, demonstrating the potential scale of the impact of ash dieback.

Notably, while only 2.5% of local authorities planned to fell over 5,000 trees in the two years following the survey, this rose to 24% in the next 3-5 years and 33% in the next 6-10 years. Similarly, costs were expected to increase over time, with 35% of local authorities anticipating costs of over £1 million pounds to carry out works needed in 6-10 years’ time. This highlights that local authorities envisage this to be a significant and ongoing issue. As such, strategic planning is essential to manage the level of intervention and resource that will be required over this period.

As the ash dieback epidemic has progressed, so too has the requirement for guidance. Many local authorities are now taking action to deal with ash dieback and are also considering how best to assist their treescapes to recover from the loss of large numbers of ash trees.

© Nick Organ, Tree Maintenance Ltd

Local authority carrying out mechanised removal of diseased ash in Newport

This toolkit, as with the previous ash dieback toolkit, relies on materials and resources which have been generously provided by a wide range of local authorities and agencies who are dealing with the problem. Examples of good practice are given throughout this document, alongside guidance and lessons learnt from their own experience. We hope to provide continued updates to this content, as the situation develops further, and would always welcome suggestions for new content or case studies, so please do get in touch

The toolkit is structured in the following way:

• Part 1: Raising awareness and understanding ash dieback

• Part 2: Creating an Ash Dieback Action Plan

• Part 3: Taking action

• Part 4: Planning and implementing a recovery strategy

Woodland in early summer showing the abundance of diseased standing ash trees

Experience from local authorities over recent years has shown that taking a strategic and sustainable approach is needed when tackling challenges faced by ash dieback.

To make the case for organisational time and resources to be spent on developing an Ash Dieback Action Plan (ADAP), landowners must first understand the potential impacts on their organisation or area. This involves:

• Step 1: Learning about ash dieback and deciding if it presents a risk to an organisation and its practices/procedures, particularly in relation to public safety. This includes understanding the disease, how to identify it and where it is found.

• Step 2: Assessing the scale of the impact on the organisation (e.g. understanding how many ash trees you own or manage). This includes how to collect data and estimating the number of ash trees and the potential cost of dealing with the actual or predicted impacts.

• Step 3: Where necessary, making the case to managers/ budget holders for an ADAP to be created to deal with the issues that will arise. This includes assessing corporate risk.

Step 1: Learning about ash dieback

WHAT IS ASH DIEBACK?

Ash dieback is a fungal disease, caused by the invasive fungus, Hymenoscyphus fraxineus (formerly Chalara fraxinea). It was first recognised in the UK in 2012, but evidence now suggests that it was present as early as 2004/2005 (Wylder et al 2018)3. Since surveillance began in 2012, it has spread quickly across the British Isles, and is now found across England, Scotland, Wales and Northern Ireland. A map showing the distribution of confirmed ash dieback infections has been produced by Fera Science and is available on their webpage. Note that this map only shows confirmed infections, so the true distribution is likely broader.

The impacts of ash dieback are concerning, as ash is one of the most common broadleaf trees across the UK. Prior to ash dieback there were estimated to be 27.2 million ash trees outside of woodlands, and ash was found to be the second most common tree in small woodland patches, and most common hedgerow tree (Maskell et al 2013)4

The fungus infects European ash (Fraxinus excelsior) and in the majority of cases will lead to mortality. Airborne infection can occur through the leaves during the summer months, and leads to leaf wilting. The fungus can then spread into the xylem and phloem of the tree, affecting its ability to transport nutrients and water. This then leads to dieback of shoots and twigs, and progression to crown dieback over the course of multiple annual infections. The fungus overwinters in the infected fallen leaves and then fruits in the early summer, releasing ascospores which go on to infect new trees. Infection can also occur through the root collar at the base of the tree via lenticels, and this is likely the cause of basal lesions seen on infected ash. Mortality can occur as a result of dieback, girdling or secondary infection by other pathogens such as honey fungus (Armilllaria sp), Ganoderma sp. and shaggy bracket (Inonotus hispidus).

Fallen leaves decompose, but the mid-rib of infected leaves is preserved until the following spring

3Wylder et al (2018). Evidence from mortality dating of Fraxinus excelsior indicates ash dieback (Hymenoscyphus fraxineus) was active in England in 2004–2005. Forestry: An International Journal of Forest Research 4Maskell et al (2013). Distribution of Ash trees (Fraxinus excelsior) in Countryside Survey data

Basal lesion of infected ash tree

EVIDENCE OF GENETIC RESISTANCE AND FACTORS AFFECTING DISEASE PROGRESSION

Despite the spread of ash dieback, some trees appear to be demonstrating degrees of genetic resistance to the fungus and there is also evidence that progression of the disease may be affected by other factors. One of these may be the position of the tree in the landscape. Work in France has suggested that ash trees growing in a less dense canopy structure – either because of low stocking densities or as a result of being an isolated tree in an urban area or a tree in a hedgerow – are less susceptible to the disease and experience slower progression (Grosdidier et al 2020)5. This may be linked to the microclimate experienced by the trees, as high moisture levels (which are found for example in shaded woodland) are correlated with increased severity of ash dieback (Grosdidier et al 2020; Cracknell et al 20236), and higher temperatures are correlated with lower levels of ash dieback (Grosdidier et al 2020). Notably, this evidence was gathered in a region with higher summer temperatures than are currently experienced in the UK, and so may not be replicated in our treescapes. As well as the possible impact of temperature, isolated trees may experience lower exposure to fungal spores as there are fewer neighbouring sources of the fungal infection.

Individual tree physiology also influences severity of infection, with larger trees and those with faster growth rates experiencing lower levels of crown dieback (Cracknell et al 2023; Klesse et al 20207).

This can be explained as the loss of leaves and hence sugar production reduces a tree’s capacity to produce large vessels as the spring wood develops. The reduction in the size of the vessels restricts the flow of water and sugars around the tree, which then reduces the capacity of the tree to photosynthesise. Inevitably these processes produce a feedback loop which result in even slower growth, less energy, smaller vessels and so on until the tree eventually dies (Klesse et al 2020).

Width of tree rings decrease at the left of the picture, demonstrating the reduction in vessel development as ash dieback takes hold

5Grosdidier et al (2020). Landscape epidemiology of ash dieback. Journal of Ecology

The speed of infection, location of the tree and availability of water and nutrients all interact to affect disease progression. The combination of these factors means there can be large differences in the severity of ash dieback infection for each individual tree, highlighting the importance of frequent and thorough monitoring.

6Cracknell et al (2023). Neighbours matter and the weak succumb: Ash dieback infection is more severe in ash trees with fewer conspecific neighbours and lower prior growth rate. Journal of Ecology

7Klesse et al (2020). Spread and Severity of Ash Dieback in Switzerland – Tree Characteristics and Landscape Features Explain Varying Mortality Probability. Frontiers in Forests and Global Change

IDENTIFYING ASH DIEBACK

While it can be easy to spot symptoms of ash dieback in younger trees, evidence in older trees may be more subtle. There are various resources available to help with this, including identification guides prepared by:

• Observatree – field identification guides and training videos

• The Tree Council – a homeowner’s guide to ash dieback

• James Hutton Institute – for a more interactive experience, researchers have created a virtual walkthrough of an ash woodland that has been infected with ash dieback. The model has been created to represent the different symptoms and stages as the disease spreads, based on the characteristics of a site in north-west Scotland.

A local authority survey of declining ash trees using the four category system set out on page 26

Step 2: Assessing the scale of the impact on your organisation

GATHERING DATA

One of the key tasks in dealing with ash dieback is to understand how many ash trees you are responsible for managing. To do this, data from various sources should be collated, and specific surveying may be required (see Action 2 – Continuous monitoring of ash). Some useful sources of data may be the Forestry Commission’s National Inventory of Woodland and Trees, Local Authority Tree Preservation Orders or Public Realm Tree Surveys, Ancient Tree Hunt data or records from the local Biodiversity Record Centre. An example of the approach used by Edinburgh City Council is given in Case study 1.

Case study 1: Edinburgh Council ash data

A review of the known data on ash in Edinburgh was undertaken by City of Edinburgh Council Tree & Woodland Officers in the autumn of 2020 as they started their process of formulating their Ash Dieback Action Plan.

An iTree survey that had been undertaken in Edinburgh in 2013 estimated a total of 712,000 trees in the city, of which 6% are ash – that’s 42,720 ash trees. The survey also estimated that 75% of city trees are in private ownership and 25% are owned by the Council. This suggests 10,680 ash trees within Council ownership and 32,040 on private land.

It also showed that there are currently 4,160 individual ash trees recorded on Edinburgh’s tree management software, however, this data is not complete, with additional survey work planned for the remaining non-recorded trees.

In addition, there are many young woodlands on Council sites which contain around 27,000 young ash trees. Ash is a very prolific species and tends to self-seed widely. They are present in every type of site managed by the Council, including parks, cemeteries, woodlands, schools, care facilities, Council depots, Council housing gardens, cycle paths, walkways and roadside verges.

It is also a species with a very large mature size – although 6% of the total number of trees may be ash, it is likely to represent greater than 6% of the total canopy cover.

Edinburgh’s greenspaces also contain a number of specimen ash cultivars, such as the weeping ash and the single-leaved ash. These are also susceptible to ash dieback, especially the weeping ash which is extremely vulnerable to the disease.

POTENTIAL COSTS OF ASH DIEBACK

Once the number of ash trees have been estimated, an approximate cost of management can be derived. When calculating this, it is important to consider all associated costs, including:

• additional survey work

• additional practical tree management costs e.g. pruning or felling dangerous trees

• additional staff time to work with private owners to ensure dangerous trees are removed

• staff time to deal with increased public reaction e.g. requests to fell

• staff time to deal with requests to fell ash trees that have TPOs or those containing Protected Species

• additional costs of any replacement planting that may be undertaken

• other additional staff or consultant costs

• additional communications and consultation needed to explain ash dieback to relevant stakeholders

Not all of these will be appropriate in all circumstances, and the outcomes of these assessments will vary with each local authority. This is demonstrated by the examples given in Case study 2:

With ash dieback, the clear up task can take longer than expected due to the brittleness of the timber.

Case study 2: Assessment of budget implications for an English County Council

6,020

ash trees recorded on adopted highway verges 83%

120,000

estimated number of ash trees in private ownership and within falling distance of the highway

1,546

ash trees recorded in school grounds

5,968 estimated number of recorded woodland ash adjacent to public areas of the recorded ash trees are 6 metres plus in size (the size that requires work to be undertaken to remove safety risks)

Assumption:

Adopted highway verges: 83% of 6020 trees x75% mortality rate @ £400 each

Private ownership adjacent to highway: 83% of 120,000 trees x75% mortality rate @ £400 each

School grounds: 83% of 1546 trees x75% mortality rate @ £400 each

Woodland adjacent to public areas: 83% of 5968 trees x75% mortality rate @ £400 each

Basic statistics: = £1,499,000 = £29,880,000 = £385,000 = £1,468,000

Cost implications of removal: = £1,662,540

Based on a free tree scheme for 83127 trees lost on local authority owned land adjacent to the highway @ £20 per tree Tree planting to address loss: 75% £354 mortality rate with average cost of removal (including inspections)

Total potential costs at 75% mortality  = £34,894,540

Step 3: Making the case for an Ash Dieback Action Plan

As well as the costs associated with ash dieback management, it is also important to consider the risks to the organisation. Given that dead and dying trees can be dangerous, the impacts of ash dieback should be considered from a corporate risk perspective. Creating an Action Plan to manage these risks has been recognised as the simplest way to ensure an organisation can effectively combat ash dieback and the problems it brings. For local authorities, the addition of ash dieback to the Council’s corporate risk register can also highlight its importance, and increase political buy-in. To assist with this process, a list of potential impacts of ash dieback that may be relevant to a corporate risk register are given in Appendix 1 based on experience with English, Welsh and Scottish local authorities.

Having an Ash Dieback Action Plan is an important step towards proactive management of ash trees and associated risk, which will be more cost-effective than reactive management. The key points below may be useful for communicating the need for an Action Plan to others in your organisation:

• Dead/dying ash trees: ash dieback is already causing a significant proportion of ash trees to decline or die. This will create a financial and practical impact for every organisation responsible for vegetation management.

• There is only a short period for preparation: ash dieback has already spread across most of the UK, and death of mature trees can happen after only a few years of infection. As such, if your organisation has not already prepared for the impacts of ash dieback, it needs to be considered as a matter of urgency.

• Early proactive work is often more costs effective than reactive management: as the difficulties and costs of dealing with diseased ash increase as the tree becomes more infected and dangerous.

• It will impact corporate risk: ash dieback will impact corporate risk registers particularly in respect of risks to statutory functions or service delivery, increased potential for deaths or injuries, budget impacts, risks to infrastructure, increased liabilities, risks to staff and ‘user’ communities, insurance claims, as well as political and reputational risks.

• There will need to be changes in management practices: dealing with ash dieback and the works required to do this will differ from the tree management systems that were in place previously.

• Working with others for efficient joint responses: the response to ash dieback needs to be planned, to avoid working in silos and conflicting with other local policies such as landscape and biodiversity policies.

• Communication and collaboration are key: a plan will provide better opportunities for communication and discussion and provide opportunities for agencies to work strategically together to share costs and responsibilities.

PART 2: PREPARING AN ASH DIEBACK ACTION PLAN

The development of an Action Plan requires a number of different approaches depending on available staff and resources. The length of time to produce a plan will also vary depending on the complexity of the organisation/area and the resources available to undertake the work.

The table below shows the process that a local authority is likely to undertake as they prepare and then deliver an Action Plan, including an estimate of the timescale it may take to achieve the task, based on experience. Many of these stages can be run simultaneously.

Step 1: Compile an assessment of your ash trees and their health

Step 2: Set up cross-organisational meetings on ash dieback

Step 3: Prepare the Plan

Step 4: Set up an internal and/or external steering group to deliver the Plan 3 months to 1 year

From discussion with local authorities since the production of the first Toolkit in 2019, many have now implemented the plans that they have prepared. A helpful list of published action plans from different tiers of local government has been collated on The Tree Council website. However, for local authorities that may still be starting this journey, full guidance can be found from page 9 onwards in Part 2 of the 2019 Ash Dieback Toolkit.

Part 2: See page 9 onwards.

RECOMMENDED COMPONENTS OF AN ASH DIEBACK ACTION PLAN

The exact nature of an Action Plan will depend upon the needs of the organisation and the issues it faces. To assist its creation, we have produced a template with suggestions for structure and content in Appendix 2.

A summary of components is listed below.

• An executive summary of the Ash Dieback Action Plan

• Priorities, outcomes and outputs

• About ash dieback: biology, spread and potential impact

• Benefits of ash trees and woodlands

• Management advice: options for managing ash dieback

• The potential impacts of ash dieback in your area including:

• Landscape and biodiversity

• Local landowners, land managers and homeowners

• Local utilities and infrastructure organisations

• Potential impacts of ash dieback on the work of your organisation and other organisations in your area:

• Health and safety impacts

• Economic impacts

• Reputational impacts

• Environmental impacts

• Recovery from the impacts of ash dieback – rebuilding a resilient treescape.

The use of high quality, impactful images of local trees in your Action Plan will help convey your key messages.

© Ian Turner, The Tree Council

© Ian Turner, The Tree Council

Action 1: Creating a communication strategy

Managing ash dieback effectively requires the involvement of a range of internal and external stakeholders with different perspectives and expertise. Collaborating with this range of individuals and organisations is key, but can be challenging. It is therefore important to develop a communication strategy, which involves:

• Identifying all stakeholders (internal and external)

• Understanding the information you need to share with them

• Deciding how to communicate this information most effectively (see Case Study 3 below for an example)

• Implementing the tools required to engage and distribute information. Examples include setting up forums (Devon Ash Dieback Resilience Forum), producing online resources (Hampshire Countryside Services video), setting up websites (Sheffield City Council).

• Internal engagement and collaboration within local authorities is vital as the expertise of different departments is required. Creating a working group or board with representatives from departments who will be involved in the response can be helpful for ensuring buy in and spreading resource need (see Case Study 4). We have found during the development of this Toolkit that it is extremely helpful to gain political support at the earliest stage for the organisation’s plans for ash dieback. This political support is usually vital to ensure resources and officer time.

Case study 3:

West Sussex County Council – Communicating with private landowners

West Sussex County Council (WSCC) has developed a consistent procedure for communicating with private landowners who have infected ash trees on their land. They have agreed a communication flowchart, for internal use, outlining their process for engaging a landowner with a tree(s) infected with ash dieback; from the initial stages, to legal notification, ongoing communication, invoicing and potential escalation. They have also created a set of letter templates for different stages of the process. An example of a letter template and the information provided to private landowners can be found, and adapted for use in your own local authority, in Appendix 3.

Although the responsiveness of landowners can be unpredictable, this approach has helped WSCC tackle uncertain or challenging situations in a consistent manner. It is helpful to have this process agreed internally and available for relevant staff to refer to –especially when different departments, such as legal teams, may need to be involved.

Case study 4: Leicestershire County Council – the importance of

internal collaboration

Leicestershire County Council set up an inter-departmental Ash Dieback Board in 2018, who could tackle a range of activities related to ash dieback. By having this interdisciplinary group, the arboricultural team have buy-in from other departments including Highways, Legal, Environment, Schools and Transport.

This has opened many internal ‘doors’ and made the response more efficient. For example, the internal project team’s new links with the highway engineering team has been invaluable in delivering complex larger scale works program across the highways network. This has ensured road space booking for ash dieback works is put in place quickly and as required to deliver the works efficiently. This is particularly important for County Councils, as different areas of council-owned land are managed by different departments, but the ash dieback response has needed to be cohesive across the whole county.

The Ash Dieback Board has also made external engagement much easier, as all the different departments can feed into one communications strategy, ensuring consistent messaging to stakeholders.

The communications strategy includes clear messages about ash dieback, particularly in relation to the county’s role as a Highway Authority. In order to meet concerns about possible implications to the road network from ash trees in third-party ownership, early communication and contact with landowners to keep them updated on issues and awareness of ash dieback is essential. The production of an advice leaflet for landowners which could be sent out as necessary was therefore an important part of this process.

DIEBACK

Action 2: Ongoing monitoring of ash

To understand how to effectively manage the ash in the landscape, it is important to have the knowledge of where ash trees are, and what their health condition is. Initial surveying and map analysis can be used to identify areas with a significant amount of ash that might be suffering from the effects of ash dieback. Once initial analysis of the distribution of ash has been carried out, areas should be surveyed to understand the condition of ash trees present there. A four-stage classification system, developed by Suffolk County Council, is now widely recognised as the most useful categorisation of ash tree health. The canopies of the ash trees are scored assessing the percentage of the crown that remains. Using this four-category framework allows a tree to be assigned to a health category, which informs subsequent potential action. The four categories are:

• Class 1: 100%–76% remaining canopy

• Class 2: 75%–51% remaining canopy

• Class 3: 50%–26% remaining canopy

• Class 4: 25%–0% remaining canopy

Further details of the four categories are available on The Tree Council website

The four categories of ash tree health assessment, demonstrating the reduction in crown foliage as the disease progresses.

Class 1

Class 3

Class 2

Class 4

All images © Gary Battell

ASSESSING ASH CONDITION IN WINTER

Whilst the optimum time to assess the condition of an ash tree is in summer, when the canopy is in full leaf, surveying can still be carried out in winter if necessary. Network Rail Scotland developed an adapted health assessment system of the four stages for use when the canopy is bare in winter:

• Class 1: Canopy intact. Rounded. Many interval branches which give a dense ‘filled’ appearance to the crown.

• Class 2: The internal structure begins to be lost as small internal branches break off. The extremity of the canopy becomes ‘spiky’ and fragmented.

• Class 3: Most of the internal branches have gone. The ends of the branches begin to become ‘spikey’, and the canopy thins from the inside out.

• Class 4: The structure of the canopy is gone. The branches that remain are spikey and show little if any branching.

The line drawings above are based on work undertaken in Germany by Professor Andreas Roloff (which formed the basis of the summer ash survey system – see A. Roloff 2001: Baumkronen. Publisher: Ulmer, Stuttgart/GER) and his descriptions of ash trees in winter.

Class 1

Class 3

Class 2

Class 4

Category 4 ash tree in winter

Visual representation of the four categories of ash tree health assessment in winter, when branches are bare

CONTINUOUS MONITORING

Locations that are high risk to people or property such as along highways, in parks, areas of high footfall and schools should be a priority for surveying. Even once sites have been surveyed, a programme of regular monitoring should be set up, involving more frequent surveys in high-risk areas (see the approach taken by Norfolk County Council in Case Study 5). This is important as ash dieback is a progressive disease, so trees which may appear healthy can sometimes deteriorate rapidly over a few years. In addition, a “zig-zag” type disease progression has been observed in some cases, where ash trees may appear to recover in seasons where fungal load is low, and then deteriorate again in future seasons.

BALANCING RISKS WITH BENEFITS

Highways need continuous monitoring

Monitoring the health and status of ash trees is a key element of dealing with the progression of ash dieback and regular surveying can also be beneficial for dealing with other tree health issues more generally. One of the most important areas to focus upon, are trees within falling distance of roads, as diseased highway trees can increase the risk of accidents.

Balancing the risk of potentially dangerous trees against the cost of frequent removal and monitoring, and the benefits of retaining ash trees can be a complex process. North Somerset Council have adopted a risk-based approach to determine which locations should be addressed first, based on the impact of tree failure, with a second level of prioritisation based on tree condition. They use a method known as a Quantified Tree Risk Assessment (QTRA).

This survey method was used as the first step in identifying potentially dangerous trees across the district which required immediate management as well as providing the data required to begin a management plan for the disease, including addressing the resource requirements and a recovery strategy. According to their QTRA approach, they will not be carrying out any removal of infected ash trees where the risk caused by the trees is low no matter what its condition. The ash will be left standing and will decline at varying rates. This creates an opportunity to increase standing deadwood which offers an invaluable habitat; and there is a chance that disease resistant trees will be identified.

More details about the North Somerset Council approach are outlined in their ash dieback plan, including a helpful decision-making flowchart to determine actions required for trees affected by ash dieback.

Case study 5: Norfolk County

Council – Survey processes and data collection

Norfolk County Council have implemented a structured survey method to monitor roadside tree safety and health, initially in response to ash dieback disease, which has now been widened to bring other tree diseases into scope. The utility of this approach was demonstrated in the 2023 season: a significant increase in the number of sycamore trees killed by Sooty Bark Disease (SBD) was observed, highlighting the severity of SDB as an emerging threat. The method is summarised below, but full details are available in Appendix 4a.

Given the length of highways in Norfolk, annually surveying the whole network is not feasible. To deal with this, the council have produced a prioritisation scale based on the level of risk associated with that stretch. High priority stretches are surveyed once a year, medium risk every two years, and low risk every four years. The risk categorisation is based on scoring the road section on the following criteria:

1. Average Height: Only trees over 5m in height and within 50m of the highway centreline are included in the surveys, as these are potentially dangerous and within falling distance of the road. For those trees greater than 5m tall, height is used as a proxy for other factors which influence the severity of the damage if the tree falls and therefore taller trees are associated with increased risk. Mean height on a section of road is determined based on the Environment Agency LiDAR data.

2. Stand density: In areas of higher density, observers are less likely to notice defects linked to tree failure, as they may be obscured by lower light conditions or neighbouring stems. Therefore, risk increases as stand density increases, and areas such as the edges of woodlands may need to be resurveyed more frequently.

3. Position on the road hierarchy: Sections of road with higher traffic flow, greater speed limits or that are important connecting routes are considered higher risk, as collisions with fallen trees would likely be more serious and falling trees or branches would cause greater disruption.

The scores from these criteria are then multiplied together to give an overall risk score, which determines the overall category. The boundaries for each category were set based on trial runs at sample sites, to ensure the output of the parameters matched the expected risk for these sites.

The data from these surveys can then be collated and compared with previous years, to understand how ash dieback and other tree health issues have developed over time. This is summarised in annual reports, with the 2023 report provided in Appendix 4b.

Action 3: Planning and carrying out major tree works and large projects

In some cases, large areas of ash will need to be cleared or worked on at once, especially where access is difficult. It is important to approach these projects strategically, as this can help to minimise the costs and ensure a more efficient process, as well as reducing the impacts on local communities

CARRYING OUT LARGE TREE WORKS

During the winter of 2022-23, Newport City Council carried out a large project to tackle the impacts of ash dieback on the treescape along the canal waterways. In total, around 1,500 trees were removed (including some non-ash trees that were considered unsafe after the removal of affected ash trees) at a cost of approximately £900,000. The Council’s Planning checklist for any large tree works is available in Appendix 5 and the main recommendations are shared below.

• Take a strategic approach: The project was thoroughly planned to ensure actions were carried out in a logical manner. The canal was split into three sections which were worked on sequentially to minimise disruption, but carrying out the works as one large project made the logistics easier and reduced pressure on areas such as traffic management and resident engagement.

• Ensure that there are specialists involved:

- Ecologists: the lead ecologist for the project carried out surveys prior to the works to identify any issues e.g. protected species, and to give recommendations for reducing impact, such as leaving veteran stumps and cutting bird and bat boxes into them. Monitoring is continuing to assess the success of these interventions.

- Geologist: a soil survey was carried out prior to works commencing to determine how much weight the towpath could take and ensure equipment was suitable.

- Communications team: the arboricultural officer worked with the council communications team and local journalists to ensure that residents and users of the towpath were well-informed about the works.

© Nick Organ, Tree Maintenance Ltd

Planning for complex works to remove infected trees is vital

- Contractors: the contractors who carried out the tree works were all selected from the council’s approved list, as trusted individuals.

• Get senior management and councillors onside: Funding for the project and the council’s ash dieback response generally was accomplished by highlighting the risk of unsafe trees, and demonstrating how a proactive, strategic removal project would minimise costs longer term as ash trees could be removed before they became too difficult to fell.

• Include replanting in the works strategy: Replanting was carried out immediately (within a week) after felling and was sequential with the felling work, following on immediately behind. This improved relations with residents as they could see that felled trees were being immediately replaced. The replanting process was carried out in partnership with the veteran’s charity Green Task Force, which also encouraged local support.

Carrying out works to remove dangerous ash on a large scale can be logistically challenging, and requires careful planning

© Nick Organ, Tree Maintenance Ltd.

IMPLICATIONS OF ASH DIEBACK ON AN SSSI

Norbury Park is an area of historic parkland and woodland in Surrey, covering 531 ha. Roughly 25% of the woodland is estimated to be ash, and so the site has been impacted by ash dieback. In 2019, Surrey Wildlife Trust made the decision to carry out extensive felling works in response to the public safety risk posed by infected trees. Selective felling of ash trees within thirty metres of public footpaths, bridleways, roads and boundaries to neighbouring properties was undertaken. By the end of the programme c. 5 ha of ash trees were removed - although a significant number were retained due to signs of bat activity or because they were not yet showing symptoms of ash dieback.

Unfortunately, these works received a significant amount of negative attention from the press and the public, which led to ongoing difficulty with the management of the site, due to the negative public reaction. In 2020, the site was handed back from the Wildlife Trust to Surrey County Council, who have been responsible for the ash dieback response there ever since.

In order to try and improve attitudes of the public towards the tree works, Surrey County Council have put in place a communications plan, led by the Visitor Services team. This involved the following actions:

• Communicating with local press

• Leading “ash dieback walks” for local residents, to inform them about ash dieback and the necessity of the tree works

• Providing additional information about ash dieback on the Council website

• Creating a video about ash dieback which was also available on their website

• Producing site notices and warning signs in areas where risk may be particularly high

• Running a community workshop on ash dieback for interested parties in the local area, as well as onsite drop-in sessions

Undertaking work may generate significant publicity, so it is important to have a communications plan.

© James Wade

The site has also produced challenges balancing public safety and biodiversity. Norbury Park is a Site of Special Scientific Interest (SSSI) and also home to legally protected species, including dormice. This complicates carrying out tree safety works, as certain interventions could contravene wildlife legislationnamely the Wildlife and Countryside Act 1981 and the Conservation of Habitats and species Regulations 2017.

Since in some instances, tree safety work has not been possible because of the protected species, access to certain areas of the Park has had to be restricted due to the presence of unsafe trees. To ensure the correct decisions are made for the park and the public, the Countryside Estates team are collaborating with other parts of the council, including in-house ecologists, other officers, and councillors, to develop the final management strategy.

GUIDANCE FOR MANAGING SSSIS WITH ASH DIEBACK

The need for additional guidance around managing declining ash on SSSIs has led to Natural England and the Forestry Commission producing specific guidance for managing SSSIs and ancient woodland with ash dieback. The principles may also be helpful in other circumstances where ash woodland is managed for biodiversity. Some of the key principles are summarised in the steps below, but the full document should be taken in its entirety by managers of these woodlands.

• Step 1: Determine the feature of interest – What are the notified features of interest for the SSSI? This could be for example because they are a good example of ash woodland, or because they have a rich and diverse ground flora.

• Step 2: Assess existing composition and threats –This involves assessing the existing composition of the woodland and undertaking health and safety assessment.

An SSSI where the ancient yew trees are threatened by the dying ash

The recommended management at this point includes retaining all (or as many as possible) ash trees with crown more than 50% healthy; retaining at least 30 healthy seed trees for as long as possible; encouraging natural regeneration and actively managing deer.

• Step 3: Assess future composition – Consider the current composition and evaluate which are the dominant species. Promote the growth of other native species currently on site and consider whether there are any other native tree or shrub species that you would expect to be present given conditions but are absent.

• Step 4: Introduce new (or presumed missing/lost) species – The preferred method for this is natural regeneration, but where this fails, planting or direct seeding of native species with local provenance is acceptable. When introducing new species, the rationale should be to support an existing, threatened species that is already present – naturalised species that are not already present should be avoided, unless it is specifically to support a threatened species on site, and there are no native alternatives that could be used.

• Step 5: Management choices – various management options can be considered depending on the context, but minimum intervention across the whole site or clearfelling are not advised by the Forestry Commission or Natural England. Some approaches that may be beneficial include “normal thinning”, with the healthiest ash retained; continuous cover forestry – this also preserves carbon in the soil; traditional management, for example coppicing with standards.

Managing

Action 4: Trees and the highway

It is estimated that the health and safety implications of roadside ash could cost £5.3 billion. National Highways alone estimates that there are at least four million ash trees next to their road network, of which approximately 660,000 are estimated to fall onto roads in the next 30 years (see Road Closure Report summary below).

To tackle this issue, in 2020 a Defra initiated ‘Ash Dieback Road Closure Taskforce’ was created to bring together key stakeholders across central government, local government and landowner groups. The taskforce reviewed the issues associated with managing roadside trees and published a report in March 2021. The recommendations are summarised in the table below. For those involved in planning the response to ash dieback along roads, it is recommended to read the Taskforce’s full Ash Dieback Road Closure report.

Diseased ash on the highway can present serious health and safety issues

Summary of local authority recommendations identified by the Roads Closure Report (Ash Dieback Road Closure Taskforce 2021).

Theme Recommendations

Theme A

Raising awareness

Theme B

Funding & resources

Theme C

Planning & coordination

Raise awareness and share road closure best practice across local government. Use strategic risk registers to communicate budget impacts and safety risks to senior leaders.

No specific recommendations for LAs, but the report highlights the potential benefits of more streamlined and coordinated processes. For example, undertaking larger projects with fewer road closure applications.

Bring people together to discuss ash dieback response, such as ash dieback project boards and stakeholder groups.

Provide a central point of contact (e.g. ash dieback officer).

Develop a coordinated approach to tree removal along strategic routes (see example in the report). Review highway survey regimes, ensuring they are inspected at the most appropriate time of year and often enough.

Theme D

Legislation & guidance

When serving statutory notices to private landowners, also provide them with guidance on legal responsibilities to incentivise prompt action.

ASH DIEBACK ALONG PUBLIC RIGHTS OF WAY

Public Rights of Way (PROW) enable people to travel on foot or by bicycle, and to enjoy the countryside and green spaces. Many local authorities have significant networks of footpaths, bridleways and trails to manage; some of these have a significant presence of ash trees.

Managing ash dieback along the PROW network has emerged as a topic of concern and uncertainty. It can be too expensive and time-consuming to frequently inspect footpaths and bridleways, and methods that can be appropriate for assessing ash dieback along roads, such as drive-by surveys or desktop studies, are less suited to PROW. Therefore, the distribution of ash trees and the presence and severity of ash dieback is often less well understood, making the risk to the public difficult to assess. Alternative solutions may be needed to fill this knowledge gap, such as working with trained volunteers or encouraging walkers, riders and cyclists to report any concerns about dangerous trees.

A series of research workshops were held by The Tree Council and Fera Science in 2022 to bring together local authorities and other organisations facing ash dieback challenges along Public Rights of Way. 140 officers participated from 65 towns, boroughs and counties across England. The discussions revealed key challenges and possible solutions, and practical steps local authorities are adopting to manage the risks. See Appendix 6 for a summary of the research workshop findings.

There are also additional cost and challenges; for example, charges for closing PROW, and difficulties with accessibility for large machinery. As such, proactive inspections and strategic prioritisation of works could save local authorities money. If tree works are needed, there could also be a high risk of public objection, as footpaths and trails often pass through sensitive locations (e.g. a nature reserve) and the trees may be well-loved by local residents. Effective public communication is therefore essential (see resources produced by Sheffield City Council in Case study 6).

Case study 6: Guidance for the public

Sheffield City Council developed communication materials to ensure consistent messaging for members of the public. They have an information page on their website, which sets out how they manage ash dieback and provide a link to their Action Plan. They have also produced two posters – one with general information on ash dieback and the other to provide advance notice of upcoming works. This approach can help reduce misinformation and help local communities understand why trees in their area need to be made safe.

The Tree Council has also prepared two ‘Ash Dieback Guides for Tree Owners’ (one for England and Wales and one for Scotland) to provide advice for land managers, including householders and practitioners, who have responsibility for the management of individual and small groups of ash trees.

Action 5: Preparing and delivering a tree strategy

The spread of ash dieback encouraged local authorities to consider their treescapes in the wider context, and this resulted in the development or updating of many local tree strategies (see Kent County Council in Case Study 7). However, it also became clear that there was a need for coordinated guidance on how to develop a ‘Tree Strategy’.

In 2023, Defra funded The Tree Council, Fera Science, Forest Research, the Forestry Commission, local authorities and other stakeholders to develop a Trees and Woodland Strategy (TAWS) Toolkit. It is a step-by-step guide for local authorities and their stakeholders to develop and deliver a local tree strategy and harness the longterm benefits that trees can bring to local communities. It provides practical guidance, insightful case studies from ten local authorities around the country and an array of other useful resources.

TREES AND WOODLAND STRATEGY TOOLKIT

Step-by-step guidance for local action

The Trees and Woodland Strategy Toolkit

Examples of the way ash dieback has been referred to in recent local authority Tree Strategies include:

• Hampshire County Council – Recognises that ‘ash dieback is a major issue for tree stocks in Hampshire county and that it will need to be carefully managed through existing strategies and a coordinated approach to ensure that both the loss in biodiversity and landscape character are mitigated’ (page 5).

• Hertfordshire County Council – Ash dieback is mentioned several times in their Tree and Woodland Strategy, for example it’s noted as a threat to Hertfordshire’s treescapes (page 85).

• Derbyshire County Council – Includes a section on ash dieback and its implications in Derbyshire, links to their Ash Dieback Action Plan, and says the effective delivery of the Action Plan is integral to their tree strategy (page 26/27, and in their actions page 61).

Case study 7: Kent County Council’s tree strategy

2016 saw preliminary scoping work for a Kent Tree Strategy, which was formalised as an agreed action within the multi-agency Kent Environment Strategy Implementation Plan 2017. The Kent Resilience Forum Ash Dieback Strategic Coordinating Group acquired the lead responsibility for delivery of the tree strategy.

A framework for the Kent tree strategy was agreed and baseline data established in 2017, with the final Plan Tree – Kent County Council’s Tree Establishment Strategy completed in October 2022. It sets an ambition for Kent to extend tree cover by 1.5 million new trees and increase the county’s average canopy cover to 19%. Through extending tree cover in Kent and delivering this strategy, they aim to:

• contribute to Kent County Council’s, and the country’s, net zero targets

• reduce and reverse the trend of decline in nature and loss of trees

• tackle the multiple threats to our trees

• deliver nature-based solutions to some of the county’s challenges

• provide enhanced and improved recreation and amenity

• address the decline in trees outside woodland and decline in urban trees

• realise the economic benefits of increased tree cover

• increase our knowledge and provide better protection for Kent’s trees

Action 6: Dealing with waste timber

The increasing number of infected ash trees being managed across the country, is resulting in the production of large amounts of ash timber. There are currently no restrictions on the movement of ash timber within the UK, making it a useful resource as sales of woodchip and logs can produce revenue to supplement funding for ash management.

Case study 8: Hampshire County Council – What happens to the timber?

One of the consequences of dealing with diseased trees is the production of large amounts of ash timber. Hampshire County Council have been ensuring that this resource is not wasted, with various different approaches being used depending on the circumstances. The first, and simplest approach, is to leave felled timber to create deadwood habitats, along with small brash piles which can also be important for biodiversity. This is the most suitable course of action for areas of woodland, or other locations where deadwood will not be a hazard.

In locations where leaving deadwood is not viable, or where there is too much deadwood already, the timber is processed for commercial use. Depending on the grade of the timber, some is sold as wood chip and some as firewood. The highest-grade logs can be sold as sawlogs which are eventually used in the furniture sector. The brash is also chipped and can then be sold for use in large biomass boilers. The council try to keep suppliers and consumers within Hampshire – with one of their customers being Marwell Zoo, who use the biomass chip to heat their tropical house and keep their animal residents warm. Not only are these sustainable uses for the leftover material from tree works, the revenue from selling timber can be used to boost the funding used for management and replanting.

Work being undertaken in Hampshire, creating considerable amounts of timber.

Action 7: Ash dieback and worker safety

In anticipation of a greater number of ash trees requiring removal across Scotland over the coming decade, Scottish Forestry, the Ash Dieback Risk Group (Scotland) and The Tree Council, have jointly developed a Guidance Note to assist those actively carrying out tree works on infected ash trees.

It draws upon experience from professionals already working on these trees and outlines some of the tree work methods that have been adapted to reduce risk to ash workers. It is not designed to provide a definitive tool on how to deal with the felling of infected ash trees but can be used in conjunction with enhanced risk assessments and health and safety guidance. The main insights of the document include the specific risks associated with ash dieback:

• Infected ash trees are reported to be increasingly brittle and behaving differently to healthy trees, and even trees with early-stage infections are increasingly unpredictable.

• As ash dieback progresses within a tree, working on diseased ash becomes increasingly hazardous.

• As the canopy condition declines, diminished hinge integrity in infected

• trees is also making them less predictable to fell safely and increases the

• risk of potentially fatal incidents without additional precautions.

• As the canopy declines, climbing trees with rope and harness cannot be

• recommended due to the increased likelihood of anchor point failure.

• Vibrations created when working under infected ash can lead to deadwood falling from canopy.

• Typical working methods e.g. the use of wedges, may now increase risk of limb and stem failure.

As a result of these risks, increased use of mechanisation is strongly recommended during the felling operation to reduce the likelihood of harm to operators. Work on an infected tree is much safer when undertaken by machinery with Falling Object Protection Structures including cranes, grapple saws, harvesting heads and Mobile Elevated Work Platforms that can protect the operator.

Chainsaw operations and tree climbing with ropes and harness, should be kept to a minimum and only carried out by the most competent, skilled and well-equipped operators. This guidance outlines changes to the conventional layout and organisation of the work area which are also becoming necessary to protect all parties from the risk of falling objects, including increased working distances, felling in the direction of the tree’s lean, and larger escape routes.

It is important to note that these points are for guidance purposes only and must not be relied upon as each tree, and the risks it poses, must be professionally assessed on site.

Trees outside woodlands are particularly important for resilience in a treescape, as linear features such as hedgerows and riparian corridors increase connectivity, allowing populations of species to move between suitable habitat and reducing the impact of losses of individual trees or patches (Plenderleith et al 2022)8.

An ash dieback recovery strategy should also be produced with biodiversity in mind – there is no single species which can completely replace the niche of ash in the landscape, but a mix of other native tree species can help to provide some of the same benefits – see below (Mitchell et al 20169; Broome et al 201810). The best choice of species will depend on the location – for example, considering soil type, climate resilience and other tree health issues. Context is also important, as within woodlands, loss of ash may mimic natural canopy thinning, and therefore recovery may be possible without the need for planting.

8Plenderleith et al (2022). The consequences of tree disease and pre-emptive felling on functional and genetic connectivity for woodland invertebrates. Ecological Informatics

9Mitchell et al (2016). How to Replicate the Functions and Biodiversity of a Threatened Tree Species? The Case of Fraxinus excelsior in Britain. Ecosystems

10Broome et al (2018). Responding to ash dieback (Hymenoscyphus fraxineus) in the UK: woodland composition and replacement tree species. Forestry: An International Journal of Forest Research

UNDERSTANDING THE IMPACTS OF ASH LOSS ON BIODIVERSITY

Ash trees are an important native species, and the third most common species in Britain after oak and birch. They contribute to a variety of ecological communities including broadleaf woodland, riparian habitats and hedgerows. Ash forms ecological associations with at least 955 other species and is a particularly significant host for lichens and fungi, due to the high pH and high nutrient content of its bark (Mitchell et al 2014)11. A list of the 955 ash-associated species and the other trees that they may be able to use instead is provided in a spreadsheet in a Natural England report

While 45 of these species are considered ash obligate (i.e. reliant only on ash), for many of them, other trees can also provide the same services that ash provides, such as food, nesting locations and habitat. Therefore, managing your treescape effectively to provide the appropriate species mix can help to support ash-associated biodiversity in the face of declining ash numbers. A 5-step process has been developed by researchers to help identify the changes in management required, and is outlined in section 9.2 of the Natural England report. The procedure has also been followed at 15 case study sites across the whole of the UK, and the findings from these case studies are available to download via the Natural England website

IMPACT OF ASH WORKS ON BIODIVERSITY

As well as considering mitigation strategies for ash loss, it is important to consider the impact of ash dieback related tree works on biodiversity. Felling of trees, along with the use of heavy machinery and the associated damage and noise pollution can all have adverse effects on wildlife, so it is important to consider how these can be minimised.

One particular risk that can occur is when diseased ash trees can fall and damage adjacent ‘ancient’ or otherwise important trees. This has become particularly important in, for example, ancient yew woodlands in southern England. Here care has been needed to ensure that any ash trees that fall naturally, or are felled, cannot damage other important healthy trees (see picture on page 42).

The following guidance is based on approaches taken by various local authorities when removing or managing diseased trees.

• Consult with ecologists before, during, and after works, e.g. Surrey County Council works with their in-house ecologists to survey affected areas for use by birds, bats or other European protected species (see Norbury Park approach on page 31), which may influence the course of action taken when carrying out tree works. Ecological monitoring after works can provide evidence of their impact, which can then be used to inform future decision making.

• Plan tree works in advance, to give enough time to consider how to minimise their impact and carry out any necessary pre-checks and surveys.

• Carry out the tree works outside of bird nesting season where possible, as work carried out at other times may impact nesting birds and infringe the Wildlife and Countryside Act 1981 and the European Habitats Directive 1992/Nesting Birds Directive.

• Leave standing deadwood and brash piles, as these provide important wildlife habitats.

• For large trees, removing just dead branches or monolithing can help reduce the risk. These retained trees may still be somewhat resistant, making their genetic contribution potentially beneficial to landscape recovery. However, if they die, they can still provide standing deadwood as valuable habitat with reduced risk. There is still considerable uncertainty about the health risks created to the remaining tree as a result of this treatment, with anecdotal early evidence suggesting both that:

– In some cases, there was a greater risk to the remaining tree as the branch lengths were shortened reducing the distances the pathogen had to travel to impact the main stem

– Whilst in other cases, some positive impacts were seen with ancient pollards seeming to remain healthy despite the disease passing through an area

• Plan to replace lost ash with appropriate species to your local environment.

Fallen ash in ancient yew woodland damaging important ancient trees

Case study 9: Considering European Protected Species

There are multiple species, including dormice and all bats, that are European Protected Species (EPS), and so are protected by law under the Conservation of Habitats and Species Regulations 2017 and the Wildlife and Countryside Act 1981. Depending on the work that is being undertaken, a licence may be required to fell, prune or pollard ash trees.

European Protected Species licences will only be granted in cases where there is a licensable purpose (such as public health and safety or for prevention of serious damage) and where there are no satisfactory solutions which do not required the use of a licence. The applicant will also need to demonstrate that there will be no adverse impact on the overall favourable conservation status of the species concerned. There are a number of different resources available to provide guidance when dealing with forest operations or tree works around European Protected Species:

• Bat Conservation Trust Guidance on managing and surveying woodlands with bats

• Forestry Commission EPS checklist

• Forestry Commission and Natural England guidance on managing and protecting woodland wildlife

• Scottish Forestry guidance page for wildlife and forest operations

MAXIMISING RETAINED ASH NUMBERS

While felling of ash trees to reduce or remove risk is one facet of ash dieback management, it is important to remember that retaining as much ash as possible in the landscape is still the goal. Retaining ash is vital for the future survival of ash trees in the landscape, and for resilience to future pests and climate change. Where there is no risk to people or property, ash can be left even when the disease has progressed significantly.

Conserving ash trees where possible is important as it not only keeps the habitat available for ash-obligate species, but also maintains a high level of genetic diversity in the population. The current mature ash tree population provides a seed source for potential natural regeneration. Every time trees reproduce, and the seeds grow, there

is huge amount of variation in the genetic makeup of the individual seedlings. This means that some may have combinations of genes which make them better adapted for current conditions, for example by being resistant to ash dieback or more resilient to challenging climatic conditions. Even ash trees that are not particularly resistant to dieback may harbour important genetic resources for future generations, for example increased tolerance of future pests and diseases. As such, ash seeds hold the possible future of the population which is why it’s vital to retain as many healthy trees as possible.

When monitoring your ash tree population, it is therefore necessary to balance the risks, with the important conservation aim of retaining as many ash trees as possible, when safe to do so. The Quantified Tree Risk Assessment approach used by North Somerset Council (see page 27) is an example of this.

Genetic resistance to ash dieback will not come from just one or two genes, but rather from the additive effects of many hundreds or thousands of genes working together. Therefore, to ensure ash remains in the landscape, we need to keep as many healthy-looking trees as is possible, so that their genes can recombine into healthier trees for the future. However, this means that not just those that look very healthy (Class 1 trees), but also some Class 2 trees - those that only look good or ‘OK’ – should be retained if safe to do so, as they might contain valuable genes too.

In the seeds and healthy seedlings of ash lies the potential for future resilience, potentially producing resistant young trees - as may be happening here on Network Rail land in north London.

Case study 10: West Sussex County Council – Factors to consider when retaining ash

The ash dieback team at West Sussex County Council have attempted to retain ash trees where possible and their decision-making has been based on the following points:

• Location – is the tree in a location where it causes greater risk (e.g. highways, schools)?

• Stage of disease – which of the four stages of ash dieback progressions is the tree at? If at stage 1 or 2, the trees are most likely to be retained.

• Management – if the tree is at a later stage, can it be pruned, pollarded or left as a monolith, even if it is too unsafe to leave the whole tree?

After making the decision to retain an ash tree, the County team believe it is important to frequently monitor its condition, to ensure that it has not deteriorated to a point where it has increased the risk. In West Sussex, they have followed the following protocol:

1. Flag the retained tree on their monitoring system and mark its location to ensure there is no confusion. Note the stage and condition of the tree.

2. Set a reminder to return to the tree in 3 months.

3. Return to the tree after the allotted time, and re-assess, to check no further works are required. Note the current condition of the tree.

The County team then record the changes in the condition of a tree, as despite appearance of recovery, a tree may quickly decline again – as signs of recovery are not necessarily evidence of resistance. As a result, trees which appear safe, could still deteriorate to a condition where they are dangerous, so frequent monitoring is needed.

STRATEGIC RESPONSE TO ASH LOSS

When thinking about a recovery strategy from ash, it can be useful to tie this into a broader Trees and Woodlands Strategy (TAWS). The Tree Council and partners have produced a toolkit aimed to support local authorities, which provides guidance for planning, producing and implementing a TAWS (see page 36). This can be especially useful for local authorities who have planting targets, as tree planting projects can complement strategies to help the landscape recover from lost ash. Having an overarching strategy across different teams can also help with funding and capacity, as there may be crossover between different projects. For example, Surrey County Council now have an in-house ecology team funded by their Biodiversity Net Gain work, who have also been able to provide guidance on ash dieback response and their tree planting strategy.

In addition, thinking strategically can broaden the scope of ash dieback recovery work to have greater impact on local communities. An example of this is the Saving Devon’s Treescapes project, which began as a response to ash dieback, but has now expanded to be based around promoting community involvement in sustainable management of the treescape (see page 49).

CREATING A RESILIENT TREESCAPE FOR THE FUTURE

In 2018, Defra published the Tree Health Resilience Strategy as the impacts of ash dieback were beginning to be felt across the country. The strategy set out how Defra intended to:

• work to protect and value our trees as important natural capital

• put biosecurity at the heart of everything we do, from onsite activities to buying practices

• develop and apply the latest science and evidence on the full range of threats to tree health to inform our risk-based approach

• apply the principles of the environmental goals to the management of our trees, woods and forests

• build the knowledge and capability to apply the concepts of resilience at all levels

As ash dieback continues to spread, the ramifications in our woodlands and other treescapes is being felt, particularly related to the connectivity of landscapes and its impacts on biodiversity. Defra plan to publish an updated strategy in 2025 and will include new information and ideas about adaptation, exploring connectivity and the importance of genetic and species diversity for building resilience into our treescapes.

DEVON’S RECOVERY STRATEGY

In 2016, Devon County Council joined forces with organisations, communities and individuals across the county to become one of the first local authorities to agree an Ash Dieback Action plan. This Plan was subsequently updated in 2021 by the Devon Ash Dieback Resilience Forum and they developed some top priorities and principles for landscape, wildlife and natural capital maintenance and restoration.

The updated Action Plan states that “the loss of ash is likely, due to its sheer abundance, to impact heavily on landscape quality, wildlife dependent on trees, the volume of storm runoff and the summer temperatures of cities and towns. Its loss will also have an impact on soil composition, specialist lichen communities and broadleaved timber products in woodlands.”

The Forum has developed eight key principles for replacing lost ash trees:

• Act now to minimise the landscape impact of ash tree loss – start promoting new trees and taking better care of existing trees.

• Use the 3/2/1/ formula: at least 3 new trees for loss of a large tree, 2 for a medium tree and 1 tree for a small tree.

• Promote natural regeneration wherever possible, particularly in woodlands.

• Grow the right trees, in the right places, in the right ways and give them the right aftercare.

• Encourage a diverse range of trees to develop a resilient landscape. (No one species alone can substitute ash. However, aspen, alder, field maple, sycamore, birch, rowan and disease resistant elm, along with native oaks, have some similar traits.)

• When choosing species, consider local factors such as what trees are characteristic of the area, soil type, management requirements, local stresses, etc.

• For wildlife, landscape and woodfuel, choose native species, or those well established in the British Isles such as sycamore, wild pear, crab apple or white willow. In urban areas it is more acceptable to use species from other parts of the world.

• Reduce the risks of introducing new diseases by only planting trees sourced and grown (UKISG) in Britain.

The Devon Ash Dieback Resilience Forum has also produced a number of useful guidance notes which are available on their website

FUNDING RESTORATION OF THE LANDSCAPE

A key part of recovery from ash dieback and building more resilient treescapes is planting – both to replace lost ash, but also to maximise the benefits of new trees. Funding for planting can be available from a number of sources depending on the context. Since 2019, Defra and the Forestry Commission have provided funding for tree and woodland planting aimed at local authorities and other landowners in the form of the Local Authorities Treescapes Fund, the Urban Tree Challenge Fund and the England Woodland Creation Offer. The grants for non-woodland tree planting are currently under review and future opportunities will be announced in due course.

Details of all government tree planting and woodland creation funding opportunities can be found on the Gov.UK website. The Tree Council and the Woodland Trust also offer tree planting grants, support and guidance.

Replanting of woodland after removal of dangerous ash trees by the road.

Case study 11: Saving Devon’s Treescapes

To deliver recovery in Devon, a project was established called ‘Saving Devon’s Treescapes’ led by Devon Wildlife Trust on behalf of the Devon Ash Dieback Resilience Forum. It is a partnership project supported by The National Lottery Heritage Fund as well as other funders, which demonstrates the value of collaboration and working at a landscape scale when planning and delivering a recovery strategy.

The partnership was set up in 2020 as a response to ash dieback, in recognition of the change to Devon’s treescape that would occur through the loss of the majority of their 1.9 million mature ash trees outside of woodlands. While originally set up to replace lost ash trees, it has now evolved to a broader project to involve the community in sustainable management of the treescape. The project aims to plant and nurture 250,000 trees outside of woodlands by 2026, through a range of activities. These initiatives include:

• Landowner visits: a member of the team will provide advice on management, restoration, planting, and which grants to apply to do this.

• Citizen science: coordinating surveys of notable trees, butterflies, lichen and bats.

• Free tree schemes: “Tree hubs” run by volunteers (including local Tree Wardens) for distributing free trees for planting in gardens or other privately owned land.

• Community nurseries: the partnership runs two community tree nurseries and have also set up lots of micro-nurseries in schools and community spaces, which grow trees from local seeds for planting in the area.

• Ash archive: for keeping the cultural heritage of the ash treescape alive, the partnership run this archive to showcase creative projects related to ash trees, including a commissioned photography series.

The partnership is promoting a 3-2-1 approach to replacing lost ash trees – planting 3 trees to replace a large ash, 2 to replace a medium ash and 1 for a young ash. So far, they have planted 50,000 trees outside of woodlands, many of these through the free tree schemes for the community. Alongside this, they have advised and supported at least 100,000 more trees to be planted through other funding streams, by making recommendations and assisting with the applications. They are also focusing on using native local trees for their replanting, including the Devon whitebeam which currently only grows in the wild in Devon, Cornwall, Somerset and Ireland. Further information is available on the Devon Wildlife Trust website.

Section 3 Conclusions

3. Conclusions

As the widespread impacts of ash dieback start to take their toll, strategic, proactive and collaborative action will be required. In addition to shortterm tactics that deal with ash loss, it is vital for land managers to consider longer-term recovery planning, and how to safeguard Britain’s precious treescapes for future generations. We will need resilient planting and visionary thinking, as well as carefully thought-out Action Plans to deal with the immediate threats to each community.

Despite local authorities across the country reporting widespread decline and loss of ash trees as predicted, signs of resilience are appearing, with healthy seedlings and individual trees persisting, albeit in low numbers. These trees will be vital to the long-term survival of the species and their retention should be a priority.

The roadmap set out five years ago, in the first edition of the Toolkit, was to proceed with careful thought, vision and proactive intervention. Many local authorities have risen to their ash dieback challenges and found effective, practical solutions to address the additional risks, significant cost and practicalities of management and the loss of biodiversity in their communities.

Working together and sharing knowledge in the face of this widespread disease is crucial. This updated toolkit presents approaches generously shared by local authorities at the forefront of taking action. We hope that these practical insights will help others facing similar challenges.

Ash dieback also presents an opportunity to develop new resilient treescapes throughout the UK, by careful planting choices when replacing lost ash. It is heartening to see that new guidance, grant funding and local delivery has moved this from theory to practice in many locations. This has been supported by the development of tree strategy guidance to support long-term planning of treescapes which is now being implemented by local authorities around the country.

Communication, collaboration and active engagement with local communities have also proven key to the success of managing ash dieback. Tree Warden volunteers and other community groups are often supporting local authorities to monitor and replant in their communities. These relationships will continue to be important as dealing with ash dieback remains an ongoing challenge for years to come.

4. Acknowledgements and disclaimer

This Second Edition Ash Dieback Toolkit for Local Authorities was commissioned and funded by Defra. It has been developed and published by The Tree Council drawing on much information from the original Toolkit, published in 2019 in partnership with Forest Research and Fera Science.

The Tree Council would like to thank all those who have taken time to contribute case study facts, figures and opinions. These include staff and voluntary members of:

• Association for Public Service Excellence (APSE)

• Devon Ash Dieback Resilience Forum

• Devon Wildlife Trust

• Devon County Council

• City of Edinburgh Council

• Hampshire County Council

• Kent County Council

• Leicestershire County Council

• Network Rail

• Newport City Council

• Norfolk County Council

• Saving Devon’s Treescape

• Scottish Forestry

• Suffolk County Council

• Surrey County Council

• Sheffield City Council

• West Sussex County Council

All photographs copyright © Jon Stokes, The Tree Council, unless otherwise stated.

DISCLAIMER

The data in this document are solely the view of the authors and contributors. The Toolkit is a continually evolving resource and the authors do not accept any liability for any loss incurred as a result of relying on its contents.

Appendix 1

Appendix 2

APPENDIX 1: POTENTIAL IMPACTS OF ASH DIEBACK ON A CORPORATE RISK REGISTER

Can be downloaded here.

Appendix 4b

APPENDIX 4B: NORFOLK COUNTY COUNCIL – TREE SAFETY AND RESILIENCE ANNUAL REPORT SUMMARY 2023

Can be downloaded here.

Appendix 3

APPENDIX 2: AN ASH DIEBACK ACTION PLAN TEMPLATE

Can be downloaded here.

Appendix 5

APPENDIX 5: NEWPORT CITY COUNCIL – PLANNING CHECKLIST FOR CARRYING OUT ANY LARGE TREE WORKS

Can be downloaded here

Appendix 4a

APPENDIX 3: WEST SUSSEX COUNTY COUNCIL – A COMMUNICATION FLOWCHART FOR ASH ON PRIVATE LAND, LETTER TEMPLATE AND INFORMATION FOR PRIVATE LANDOWNERS

Can be downloaded here.

APPENDIX 4A: NORFOLK COUNTY COUNCIL – A STRUCTURED SURVEY METHOD TO MONITOR ROADSIDE TREE SAFETY AND RESILIENCE

Can be downloaded here.

Appendix

6

APPENDIX 6: ASH DIEBACK ALONG PUBLIC RIGHTS OF WAY – RESEARCH WORKSHOP SUMMARY AND FINDINGS

Can be downloaded here.

CASE STUDY 1: EDINBURGH CITY COUNCIL

Jump to case study here.

CASE STUDY 2: ENGLISH COUNTY COUNCIL – ASSESSMENT OF BUDGET IMPLICATIONS

Jump to case study here.

CASE STUDY 3: WEST SUSSEX COUNTY COUNCIL –COMMUNICATING WITH PRIVATE LANDOWNERS

Jump to case study here.

CASE STUDY 4: LEICESTERSHIRE COUNTY COUNCIL –THE IMPORTANCE OF COLLABORATION

Jump to case study here

CASE STUDY 5: NORFOLK COUNTY COUNCIL – SURVEY PROCESSES AND DATA COLLECTION

Jump to case study here.

CASE STUDY 6: GUIDANCE FOR THE PUBLIC

Jump to case study here

CASE STUDY 7: KENT COUNTY COUNCIL’S TREE STRATEGY

Jump to case study here

CASE STUDY 8: HAMPSHIRE COUNTY COUNCIL – WHAT HAPPENS TO THE TIMBER?

Jump to case study here.

CASE STUDY 9: CONSIDERING EUROPEAN PROTECTED SPECIES

Jump to case study here.

CASE STUDY 10: WEST SUSSEX COUNTY COUNCIL – FACTORS TO BE CONSIDERED WHEN RETAINING ASH

Jump to case study here

CASE STUDY 11: SAVING DEVON’S TREESCAPE

Jump to case study here.