Ash Dieback

First confirmed in the UK in 2012, Ash Dieback is a disease affecting ash trees caused by the fungus Hymenoscyphus fraxineus. It is also known as 'Chalara'. There are a variety of symptoms and the easiest to spot are often blackening leaves, which can hang on the tree, and dead twigs and branches in the tree canopy. The fungus stresses the trees making them susceptible to secondary diseases, particularly honey fungus. Climate change or other ‘stress’ factors (e.g. drought) can then exacerbate the decline. Although diseased trees may survive in the short term, ultimately the disease is thought to cause the majority of infected ash trees to die.  Young ash trees die quickly, whilst mature trees can be killed by a yearly cycle of repeated infection. Woodland trees seem more susceptible to Ash Dieback than lone veteran trees, in hedgerows for example.

The disease makes ash trees more susceptible to secondary diseases such as honey fungus, which in turn makes them more vulnerable to other stress factors, thereby increasing the likelihood of these trees falling or shedding branches. We have also found that trees which appear only lightly infected by Ash Dieback can collapse or have large and heavy branches fall without warning.  The amount of dead wood in the canopy and the unpredictable nature of collapse makes these trees extremely hazardous to fell.  This is why we have decided to fell trees at an earlier stage than we might otherwise, to reduce risk to staff, the chainsaw and forestry operators, as well as the visiting public.

Our normal procedure for dealing with hazardous trees is to remove individual dangerous limbs or monolith* the trees, and only fell completely if essential. However, the extent of the disease and the hazardous nature of diseased trees means that this approach is no longer possible. 
*To monolith a tree means removing the entire crown (all the main branches), whilst ensuring the standing stem remains a balanced structure

Unfortunately, with thousands of infected ash trees, it is impossible to continue an individual tree-by-tree approach.  Most of the ash trees managed individually have continued to degrade, so they continue to require significant specialist monitoring and will ultimately require felling, despite our best efforts to retain them for wildlife.  The trees also become increasingly dangerous to fell as the disease progresses, so for the safety of our staff, contractors and visitors to our reserves, it is imperative for us to act promptly.

Many of these trees will become extremely hazardous over the next few years, and so signage or barriers to close paths, which could be vandalised, climbed over or removed entirely, are not adequate.  Also, in some sites, diseased trees are widespread throughout the site and closing individual paths and areas does not solve the problem.

If we close reserves, we would potentially be closing them for many years.  In many sites, this is not possible due to public rights of way.  Even reserves closed to the general public would require staff and contractors to access them for monitoring and management, so we would still need to make the areas safe.

Our reserves are incredibly important to a large number of people.  The pandemic highlighted how our nature reserves can play an essential role in improving peoples' physical and mental wellbeing, and we do not want to close sites that have been open to the public for many years, as this would remove access to the benefits that a visit to our woodlands can bring.

These felling works also create an opportunity to improve our woodland sites for wildlife. The Trust will use the opportunity to create clearings, glades and deadwood habitats to increase biodiversity, improve the woodland for wildlife and increase the resilience of the woodland in the face of climate change. Natural regeneration of vegetation will be encourage, and a new tree planting programme is planned using staff and volunteers.

We have been carrying out Ash Dieback assessments over the course of the last 12 months. During this time we have continued to operate our existing and established procedure for hazardous tree identification and assessment, and this procedure will continue to operate. Our Team and our consultants and contractors are visiting sites and identifying individual hazardous trees that pose an immediate threat and are dealing with them.  The proposed timeline to commence Ash Dieback felling has a start date of September 2022, which is in line with these assessments. This is a very dynamic issue, however, which is being constantly reviewed and it may be that we do have to close some paths, areas or sites in the future.

Even our non-woodland reserves have ash trees on site, within hedgerows or along roadsides, however, it is clearly our woodland sites that have the largest problem with Ash Dieback. As our plans progress we will make site-specific information available on this webpage so that you can find out how each WWT woodland will be affected.

We do not have a blanket policy to remove all ash trees – only those trees that pose an unacceptable risk to the public, staff or contractors, our livestock or some infrastructure. The number of trees felled and the areas affected will vary between each nature reserve.  We have some sites that are very busy, and many people walk through all parts of the woodland.  In these cases, all of the diseased ash will need to be felled.  In woodlands where we have lower numbers of visitors, and they stay on the footpaths, we may only need to fell the ash trees within a certain distance of paths and tracks.  As our plans progress we will make site-specific information available on this webpage so that you can find out how each of our woodlands will be affected.

The works will be phased over the next few years, with some felling works likely to be scheduled for Autumn 2022.

This will vary from site to site, however, the hazardous nature of Ash Dieback trees means that it is very likely that forestry machinery will need to be used in some of our woodlands. These works may look unsightly and be noisy and there may also be disruption to local communities in terms of machinery arriving at sites. It is unfortunately necessary and we will do what we can to minimise the effects. As our plans progress we will make site-specific information available on this webpage so that you can find out how each WWT woodland will be affected. We will also put up signage at each site outlining our plans and we will be more directly in touch with residents neighbouring the woodlands. 

Our nature reserves will remain open to visitors while the work is being carried out, but some paths will be temporarily closed for the safety of our visitors and our contractors.

We have press activity planned from Spring 2022.  As our plans progress we will make site-specific information available on this webpage so that you can find out how each WWT woodland will be affected. We will also put up signage at each site outlining our plans and we will be more directly in touch with residents neighboring the woodlands.

We will be working closely with local species groups and ecologists to manage the impact on protected species, including bats, badgers and dormice.

Natural regeneration of vegetation will be encouraged and there will be a programme of new tree planting by staff and volunteers.  We are also examining each woodland in turn to identify areas that can be left open to create clearings and glades and deadwood habitats, increasing diversity and improving the woodland for wildlife. Creating a varied woodland structure and replanting with carefully selected tree species will provide great opportunity for wildlife and plant species to thrive, as well as increasing the resilience of the woodland in the face of a changing climate.

The good news is that we have identified some mature healthy ash trees which we can retain and nurture.