Ash trees in the UK will survive despite a fungal disease causing “significant losses”, experts have said.
Ash dieback is occurring in most parts of the UK, the Department for Environment, Food and Rural Affairs (Defra) has said.
Dr Anne Edwards, of the John Innes Center in Norwich, said: ‘My prognosis for the ashes is that we’re not going to lose them all.
Defra said more than £6million had been invested to “advance our scientific understanding of the disease”.
It was feared the disease, first detected in the UK at a nursery in Buckinghamshire, could decimate the third most common type of tree in the UK.
Formally known as Hymenoscyphus fraxineus, it causes leaf loss and crown dieback, and was first found in Poland in 1992, arriving in Britain via wind-blown spores and imported plants, according to Defra.
This month marks the 10th anniversary of the use of DNA sequencing to confirm disease in trees at the Norfolk Wildlife Trust’s Lower Wood Reserve in Ashwellthorpe.
Over the past decade, more information has been found about the life cycle of the fungus, helping researchers understand how it spreads.
“What I’ve noticed is that there’s a huge variation in disease resistance among trees,” Dr Edwards said.
“Some trees die very, very, quickly. One puff of fungus and they were dead. But others hang on and some are fabulously healthy.”
Trees that were “socially distant” – isolated in a park or garden – seemed able to survive more than those in a group.
Dr Edwards said they now know ash trees are genetically very diverse, a factor that has helped the species.
“If you look back at Covid, some people were very, very susceptible to Covid, and some people cleared it up like a cold and had no symptoms,” she said.
“It’s like that with trees, but it’s not just one [factor]it’s a complicated genetic picture that hasn’t been fully revealed, and maybe it will be in time.”
According to Steve Scott of the Forestry Commission, it is now believed that around 25-50% of UK ash may survive.
He said in Lower Wood there was a lot of ash regenerating but there were also “lots of dead and dying trees”.
But he thought the ash would “always remain an important part of the landscape, long term.”
Dr Edwards agreed the current situation was encouraging, but said more needed to be done to circumvent biosecurity and protect trees in general.
“My prognosis for the Ashes is that we’re not going to lose them all,” she said.
“There will be losses, quite significant losses, especially in forested areas, but some will hang on, and we will rely on those to repopulate,” she said.
Defra said scientific observations in Europe and the UK meant it expected 1-5% of ash trees to show some genetic tolerance to the disease.
“Since it was first detected in the UK, the government has invested over £6 million to advance our scientific understanding of the disease and has carried out the world’s largest screening trials for tolerant trees,” a spokesperson said.
“We now have the UK’s first collection of tolerant ash trees, with over 3,000 new trees planted – a major step towards recovering the landscape.”