Ash dieback management plan

We have developed a management plan to provide information on how we will react to the dieback and manage the risks.

You can find more ash dieback information and resources, including how to report a sighting, on the Forest Research ash dieback web page.

Introduction

Ash dieback (ADB) Hymenoscyphus fraxineus, (formerly Chalara fraxinea), will likely lead to the gradual death of most ash trees within Cheltenham borough and indeed the country. The scale of death will be greater than the impact of Dutch elm disease in the 1970s. There is no way to reduce the rate of spread of infection and the demise of these native (and exotic species) of ash trees. The council can only react to this die-back.

Evidence from northern European countries shows that around 10% of ash trees have a moderate resilience to ADB, and that only 1-2% of ash trees show a high level of tolerance. The rate of decline of infected ash trees is not possible to predict and will be influenced by factors such as soil type, moisture levels and topography. Evidence from elsewhere shows that some trees will decline and dieback much more quickly than others. Some trees die within a year whilst others take several years. However, in Cheltenham, it has been noted that in areas of dense ash growth (such as Leckhampton Hill), the degree of contamination as well as the rate of decline of individual trees is most severe. Elsewhere in Cheltenham’s open spaces and parklands, the rate of infection and decline seems much slower.

As ash trees decline and die, the risk to persons and property increases due to the trees’ structural integrity becoming compromised due to the decay of their supporting roots as well as the shedding of limbs and branch work from the crown. The rate of loss of such structural integrity is unpredictable but is significantly hastened by secondary infection of trees by colonisation of other decay pathogens such as honey fungus.

This management plan is designed to be an operational working document to plan for this event so that:

Adequate resources are set aside to effectively manage this scenario into the future
Public health threats as a result of the increased risk of dead and dying trees through dead/dying tree removal/pruning, are minimised
A plan for a tree natural regeneration and/or replanting to minimise the loss of the amenity and ecosystem services provided by these trees

The anticipated loss of the overwhelming majority of ash trees will impact:

Cheltenham Borough Council parks, gardens and open spaces, cemeteries, car parks, allotments and woodlands as well as council tenant individual property gardens
Gloucestershire Highways where ash trees exist on highway verge
Gloucestershire County Council and other agencies such as Network Rail, Severn Trent and other statutory undertakers
Individual property owners where ash trees exist within domestic gardens, together with
Farmers and other landowners/managers

Ash tree distribution within the borough

It is not possible to give precise numbers of ash trees on land either controlled by public authorities across Cheltenham. There are 420 significant trees and groups of ash trees under routine inspection by Cheltenham Borough Council’s tree team. Some of these groups of trees are large (10,000+ trees) and densely populated and there is a considered variable but generally low adjacent target. Whilst such a group is recorded as one tree, in reality there may actually be several hundred/thousand ash trees of varying size and maturity

Cheltenham Borough Council assets

Most ash trees managed by the borough council exist in peri-urban and rural situations such as open spaces and woodlands. These areas often take the form of formal avenues of ash trees such as in Sandy Lane playing fields and Chargrove Lane open space. However, there are many copses and spinneys of ash of varying sizes and maturity within public open space as well as ash trees in surrounding hedge lines. Spaces such as Pittville golf course, the Honeybourne Line, nature reserves and the many suburban parks around Cheltenham are regularly used by members of the public and contain many ash trees. The frequency of use of these areas usually depends on the proximity and number of adjacent dwellings.

Benhall Woods and Leckhampton Hill in particular have an estimated high percentage population of mixed-maturity and size ash trees within several large areas. Leckhampton Hill has a frequent and dense visitor population principally made up of dog walkers, ramblers and mountain bike users. Traditionally, these users stick to the principal paths and routes, the Cotswold Way and access from carparks to the top of the hill.

It is likely that the appearance and character of these areas will change dramatically following the decline of their ash populations.

There is a relatively low ash tree population within formal parks and gardens such as Pittville Lawn, Imperial Gardens, Sandford Parks etc.

Whilst the majority of ash trees on council land (excluding woodland) are under a routine and cyclical safety inspection regime by qualified trees officers, there are large areas of borough land (such as Leckhampton Hill) where no formal system of inspection exists due to the nature and size of the area. A management plan for such areas is in place and this is supplemented by informal assessments by the council's green spaces team and is often informed by the very active friends group, Friends of Leckhamton Hill and Charlton Kings Common (FOLK) or through more social media contact. By its nature, this response is reactive.

However, in other parks, gardens and open spaces, a proactive management approach is adopted. All records of formal and routine tree safety inspections are retained for insurance purposes.

Other statutory undertakers within Cheltenham

Different levels and frequencies of tree inspection are undertaken by other statutory undertakers, for example Gloucestershire County Council, depending on the considered risk and resource allocation. Gloucestershire Highways have already commenced a programme of ash removal by roadside verges throughout the county.

Privately owned trees

There is no reason to assume that the percentage of ash trees of the total number of trees is likely to be different in Cheltenham than elsewhere. It is the second most common species of tree throughout the country and the most frequent hedgerow tree. This is likely to be as a result of its seeds ability to readily germinate as well as its ability to quickly grow in hostile and difficult environments.

The level of active privately owned tree safety assessments is thought to be very variable. Experience appears to suggest that few householders undertake any formal safety assessments of trees on their land.

It is anticipated that the level of formal safety inspection of trees on farm and other land by owners is also variable, but generally is considered as being low. As such, the potential risk of tree failure onto persons or property appears significant.

Current extent of ash dieback of the controlled population within our assets

A random sample of ash trees at various locations within the borough was made in 2019 and 2020. A survey of the extent of dieback was recorded with 4 stages of ash dieback (ADB):

100% of the crown remains (meaning the tree is not infected),
75% of crown remains (meaning the tree is infected and up to 25% of the crown has died back - Stage 1)
50% of crown remains (meaning the tree is infected and up to half the crown is dead - Stage 2)
25% of crown remains (meaning the tree is infected and up to 75% of the crown is dead - Stage 3)
0% (meaning the tree is virtually or totally dead - Stage 4)

These surveys were undertaken during mid-September when the full extent of dieback is apparent but before leaves have naturally fallen.

Survey results

The table below summarises the last sample assessment of the council's ash tree population.

Ash tree population assessment
Remaining crown%	2019 Number of trees surveyed (+ %)	2020 Number of trees surveyed (+%)	2019 Leckhampton Hill (Tree Groups)	2020 Leckhampton Hill (Tree Groups)
100	129 (69%)	115 (62%)	0 (0%)	0
75	39 (21%)	51 (27%)	4	0
50	17 (9%)	18 (10%)	10	13
25	1 (0.5%)	2 (1%)	1	2
Dead	0	0	0	0
Total	186 (100%)	186	15	15

Assuming this random sample of surveyed ash trees is representative of the total a number of important points can be made:

Most ash trees (excluding Leckhampton Hill) did not show signs of ash die back.
No trees had yet actually died as a result of dieback.
Approximately 2/3 of trees had at least 75% of their crown remaining and 10% of trees have up to 50% of their crowns intact.
Worst affected trees were on Leckhampton Hill have only 25% or less of their crowns intact.
Excluding Leckhampton Hill, the rate of deterioration of the ash tree crowns was slow.
The severity of contamination of ash dieback on Leckhampton Hill was considerably worse than other surveyed areas.
The rate of deterioration of ash crowns on Leckhampton Hill is faster than elsewhere.

There was an intention to continue to inspect a random sample of ash trees to track the development of spread of the impact however, trees officer local knowledge as well as reports of “ash dieback hotspots” are considered to be as effective a monitoring control.

Observation appears to show significant contamination of trees and associated deterioration on Leckhampton Hill which reflects the picture of roadside and other rural ash trees in the south of England. Non-empirical evidence suggests that the same lower-degree of intensity of ADB is being experienced in other urban areas in the south of Britain where there is a lower ash tree population density.

Again, observation appears to show that dead trees do not readily fail prior to significant deterioration of structurally supporting roots. However, the mechanism for felling of advanced decay trees will likely require vehicular machinery (unless tree work contractors can identify other methods of self-preservation).

Further, smaller surveys were undertaken in 2021 and 2022. However, such surveys have not demonstrated they are adding value to the overall management of the Ash tree population assets of the council. The approach therefore is the ongoing observations outlined earlier in this management plan supported by the record of works (to address ash dieback) being recorded.

For several years, the felling of ash trees has primarily been adjacent to (or within 10 metres of) the busiest foot paths along Leckhampton Hill and within falling distance of Cirencester Road.

Managing the risk

There are a range of factors which are taken into account in the management of risk, these are summarised below. It should be emphasised that risk arising in respect of trees is not static and therefore the role of observations and assessments are key. With this in mind, it is important that the council adopts a dynamic approach to managing risk and should this management plan need to be updated to respond to issues arising from observations and assessments then this will be undertaken.

Non-empirical evidence has described that the rate of colonisation of ash dieback (ADB) is severely reduced (and even reversed) if during the early stages of colonisation, the tree crown is reduced by 10-20%. To this end, the council have undertaken such crown reductions of several high-profile “landmark trees” in Sandford Park and Pittville to ascertain whether there is an alternative to complete removal of ADB-colonised trees. Obviously, this will have a cost implication to the council and as such, this is being trialled only on certain high-amenity ash trees.

Health and safety

Death or injury from falling debris onto members of public or professionals working on such ash trees
Risk to statutory functions and service delivery such as retaining safe schools, public open space and highways
Risk of damage to private and public property as a result of falling ash

Potential economic impacts

Increased liability in cases of death or injury
Increased expenditure from direct and indirect costs such as additional spend addressing ADB could have impact on expenditure elsewhere within the organisation
Increased tree work contractor prices as a result of market competition for a limited pool of skilled tree contractors
Increased direct/indirect costs due to increased flood and soil erosion risk resulting from removed ash trees
Financial costs of replanting needed to retain ecosystem services, provided by ash such as flood, urban shading, carbon storage, bio-diversity. This may be achieved at low/no cost through self-seeded regeneration of trees. This is thought to include a high proportion of the sycamore (Acer pseudoplatanus) Norway maple (Acer platanoides) and hawthorn (Crataegus monogyna) species.
Increased liability from tree failure as a result of risks to adjacent land and other third-party property

Reputational damage

Potential for disruption as a result of ash dieback management (such as closure of parts of parks/open spaces/woodlands/housing forecourts, roads etc. during tree felling/surgery works
Political and reputational damage following negative press (for whatever reason) and the consequent public outrage and anxiety
Potentially strained relationships with private owners as tree maintenance costs increase

Negative environmental impacts

Visual landscape changes and consequent reduced amenity
Loss to eco-system services such as a reduction in air quality, increased flooding, biodiversity losses, increased noise, reduced screening
Reduced carbon storage and sequestration
Reduced biodiversity from the decline of species largely or wholly dependent on ash

Because of the economic, reputational and environmental risks outlined above, ash dieback is included within the council's corporate risk register.

Time associated costs

There is a time resource demand as a result of:

Identifying populations of ash and weighting the risk to persons and property
Identifying the most appropriate trees requiring remedial work
Organising and generating work orders to fell/prune trees
Liaising with fellow officers in the green spaces and housing teams, and other relevant services beyond as well as Gloucestershire Highways, statutory undertakers, “friends of” groups etc.
Significant volumes of site visits and follow up work regarding trees in council house property gardens (where there is a high proportion of ash trees)
Liaison on matters relating to ash dieback with Wessex trees officer group (WTOG)

Actions required to address the above

Stakeholders: appropriate Cheltenham Borough Council staff, Gloucestershire Highways, Ubico managers, “Friends of” groups, ward and county councillors should all be made aware of the ADB plan for Cheltenham Borough Council controlled trees
Public awareness of ash dieback and the associated risk will be made via the council’s website. There are a number of existing publications available to help this
An ash tree related budgetary increase has been made available. This is kept under review and will be informed by ongoing observations and assessments. Should central government grants become available, the council will apply
Several tree surgery contractors who have specialist industrial tree felling machinery (timber harvester) and experience have been identified via the council’s procurement contracts, to make provision should larger areas of felling be required
Where possible, dead trees will be left standing to reduce costs and reap maximum ecological reward. As such the decision of which trees to be felled will be made on a case by case basis
Records of felling locations and associated details are retained
Trees in “high target” locations will be prioritised for felling over trees in other areas
Trees officers to keep up to date with Government/Forestry Commission/DEFRA information and training updates regarding development, spread etc.

Management of council-owned trees