‘Catastrophic’ impact of ash dieback means over 30,000 trees must be felled, says National Trust

Climate crisis means cost of dealing with tree diseases is soaring

The sparse crown of an ash tree affected by ash dieback (AFP via Getty )

British trees are under threat from the increasing number and severity of dangerous diseases that are already having a major impact on landscapes, the National Trust has warned.

Diseases such as ash dieback – a fungal disease that impacts numerous species – and acute oak decline, are among the key threats to UK woodlands that have been exacerbated by the climate crisis, the trust said.

In a statement it warned that during this winter alone, the impacts of ash dieback will lead to more than 30,000 trees being felled at a cost of more than £3m.

Ash trees suffering from the disease decay and can become dangerous to the public so many have to be cut down.

The cost has risen from £2m last year and it is expected between 75-95 per cent of all ash trees are likely to be lost in the next 20-30 years.

The trust said the growing likelihood of extreme weather due to the climate crisis was also worsening the outlook for trees, as well as “altering the landscape, costing millions of pounds to clear up and distracting from vital disease management work”.

During Storm Arwen earlier this month, a number of trees that came down as a result of the storm were found to be almost hollowed out due to disease, while thousands more were lost due to Arwen in the Lake District.

The National Trust’s head of trees and woodland John Deakin said: “We are seeing changing weather patterns of milder and wetter winters and warmer summers that are creating the ideal environment for pests and disease to spread. Increased droughts and storm events are stressing our trees, reducing their ability to resist pathogens.

“This could have a catastrophic impact on our countryside and for nature, as homes for wildlife are depleted.

“Many iconic and native species may disappear, which is why it is crucial we act now to choose the trees most suited to the places which they will become established, creating landscapes and woodlands that are more resilient to the changing weather we are likely to experience with increasing regularity.

“The spread of disease and pathogens are a real-life example of why it is so important that we do everything we can to mitigate the impacts of climate change and stick to the IPCC recommended target of 1.5C increase.”

He said that trees affected by pathogens will only be felled in areas where falling trees could pose a risk to public safety or to help stop the spread of the diseases, otherwise they are left to degrade and decay to create homes for wildlife.

“The species we are replacing ash with vary depending on the location. In natural woodland, for example, we choose species that are native to the site like field maple and lime, but in other locations we may include a proportion of species from further south in Europe that will provide similar benefits – for instance walnut.”

The trust also said that this autumn, a new disease, Phytophthora pluvialis, has been found in the UK for the first time, after it was discovered in Cornwall in November. It is also the first time the disease has been identified in Europe.

It has since been found in Devon and Cumbria, although has not yet been found on National Trust land – but experts are keeping a close eye on western hemlock, Douglas fir and several pine species that it affects.

There has also been a new outbreak of the eight-toothed spruce bark beetle in southeast England, meaning restrictions have been placed on the movement of trees, bark, wood chipping and cut foliage in some parts of the country.

Increasingly mild winters may also bring Xylella to the UK, which is particularly worrying, experts said.

It is an incurable plant disease that can cause serious stress and death in more than 150 species including oak, cherries, hollies and walnuts.

Though it has not yet been recorded in Britain, there have been major outbreaks in Europe, including in Italy where olive groves have been destroyed by the pathogen.

The National Trust’s senior consultant for cultivated plants Rebecca Bevan said: “The European Commission has described Xylella as one of the most dangerous plant bacteria worldwide, and warned that it could survive and spread in the UK.

“We have native insects capable of spreading it, and a long list of vulnerable host species, including common garden plants like lavender and roses as well as native shrubs and trees such as oak, cherry, holly and elder. Our gardens have stepped up their biosecurity measures to reduce the risk of introducing Xylella into UK where it could be devastating for our gardens and countryside.”

The trust is in the process of replanting resilient species to fill the gaps that are being left by ash dieback.

In the statement, they said: “The charity is in the process of planting more climate resilient plants and creating woodlands that have a diverse range of species in them as part of its aim to establish 20 million trees by 2030. But the charity warns that more needs to be done to tackle climate change and stick to the IPCC 1.5C recommended target.”