Ash dieback disease management along the Marriott’s Way

What is ash dieback?

Ash dieback (formerly known as Chalara) is a non-native fungal pathogen that was first identified in the UK in 2012. Sadly, it is estimated that it will eventually kill up to 95% of ash trees across the UK.

It can be upsetting to see large numbers of trees being removed. Not only does it seem at odds with the ambition to plant more trees, but it can also leave an area looking stark.

So, Norfolk County Council’s Arboricultural and Woodland Team have created this guide, so you can see why the work is necessary.

What is happening along the Marriott’s Way?

Removal of trees infected with ash dieback disease is starting to take place on the Marriott’s Way. We’re doing this to ensure the safety of path users as well as reducing damage to adjacent land and fencing.

Trees on former railway embankments are more susceptible to high levels of ash dieback for a few reasons:

• the poor diversity in the genetic make-up of the tree population
• the similar age of the trees
• the high density of trees
• poor soils and proximity to water

We prioritise work on trees in these situations if people or property could be damaged.

Why is the felling necessary?

1)    Ash dieback is a devastating disease for trees

• The disease causes leaf loss, crown dieback (the visible part of the tree, such as leaves and branches) and bark lesions
• Younger trees can be killed by the fungus relatively quickly
• Older trees can be weakened by the disease to the point where they can succumb more readily to attacks by other pests or pathogens, such as honey fungus

2)    Safety

• For the reasons above, trees with advanced ash dieback pose a health and safety risk to the public
• Working on dead or nearly dead ash trees is also dangerous to the professional tree surgeons and foresters the Council employ, so where it is clear that trees will pose an unacceptable risk in the short-to-medium-term, they may be felled with others that currently represent a high risk
• There are occasions where healthy ash within a group of diseased trees may be felled. Because they have grown with the protection of trees around them, they are likely to suffer from wind-throw if they are retained once the other trees are removed  

What is our approach to felling affected trees?

The Council’s approach has been carefully considered using a risk-based analysis of a range of innovative datasets such as:

• Lidar (Environment Agency derived data that allows us to measure tree height and density)
• the analysis of people-counters along the trails network
• road hierarchy categories
• proximity to urban centres

This means we can prioritise areas of the trails (and Highway) network with the highest densities of trees and the highest footfall or traffic. It is nationally accepted that ash trees with more than 50% canopy decline are likely to require remedial work or felling.

What about habitat loss?

The primary assessment of ash trees includes observing the trees during the summer months, inspecting the trunks and base for lesions or decay fungi (physiological and structural health). Inspectors are also trained to look out for other significant wildlife or sensitive habitats that may be occupying the trees or nearby area such as notable wildflowers, nesting birds, badger setts, water features and features that may support bat activity.

Any significant findings are passed to NCC Ecologists for their advice in how to proceed.

Will it cause flooding?

No. The rapid recolonisation and coppice regrowth ensures bank stability and flood reduction is maintained - water run-off will still be impeded by vegetation

Are there any positives?

Whilst we wish the trees didn’t have to be felled at all, the County Council are taking the opportunity to create a more diverse tree and shrub landscape which will be more resilient to future pests, diseases and the impact of our changing climate:

• Natural regeneration: Replanting schemes are always carefully considered and aim to enhance existing species to ensure an increase in biodiversity. Sometimes the most effective method is natural regeneration (where healthy trees re-establish naturally); sometimes it is replanting, sometimes it is a mix of both. Along the Marriott’s Way, a rich variety of other tree and shrub species are present and rapid natural regeneration will occur. The result will be long term biodiversity gains by opening up the tree canopy, encouraging wildflowers to grow and healthy trees to establish naturally
• Retaining healthy trees: We usually wish to retain healthy ash trees, not only for the habitat they provide, but they will also be the seed source of our future ash trees
• Deadwood habitats: Some timber and tree stems will deliberately be left on-site to become important deadwood habitats and a future biodiversity enhancement. Wood chip from the works can improve poor soil conditions.
• Research: There are two exciting national programmes carrying out research to help tackle ash dieback: Forest Research have two ash dieback trial plots on Norfolk County Council land and the John Innes Centre is running the ‘Retaining the ashes’ project (from 2017 to present day) lead by Professor James Brown.

We want to reassure the public that the removal of trees and replanting schemes are carefully considered. Although the area might look unattractive initially, it doesn’t take long for the treescape to recover.

If you have any questions or require further information, please contact ashdieback@norfolk.gov.uk