Almost all the ash trees in the UK and across Europe are likely to be wiped out by a “double whammy” of a bright green borer beetle and the fungus that causes ash dieback, according to a comprehensive new academic analysis.

The loss of the ash, one of the most abundant tree species in the UK, would mean losing even more trees than the 15 million elms killed by Dutch elm disease in the 1970s. Ash is the most common hedgerow tree, with 60,000 miles of tree lines. It is the second most common tree in woodland, after the oak, and there are many ash trees in towns and cities.

“Between ash dieback and the emerald ash borer, it is likely that almost all ash trees in Europe will be wiped out, just as the elm was largely eliminated by Dutch elm disease,” said Peter Thomas, a tree ecologist at Keele University, UK, who did the analysis, published on Wednesday, in the Journal of Ecology. “The two together are a double whammy.”

Thomas said the arrival of the emerald ash borer, originally from Asia but which has devastated North American ash and is now as close as Sweden, is inevitable: “It is only a matter of time before it spreads across the rest of the Europe – including Britain. Our European ash is very susceptible to the beetle and the beetle is set to become the biggest threat faced by ash in Europe – potentially far more serious than ash dieback.”

Facebook Twitter Pinterest Close-up of an emerald ash borer beetle. Photograph: Solent News/REX/Shutterstock

“It is quite a big beetle, originally from Asia, and can fly a long way. In the past, insect diseases have spread very quickly,” Thomas told the Guardian. He said attempts to halt its spread in North America, by trying to catch male beetles in traps baited with female pheromones for example, have failed.

Ash dieback was first reported in the UK in 2012 but given the large number of sites it was found at, it must have arrived earlier, Thomas said. It remains unclear how many ash will die, as it can take years for mature trees to succumb. But 95% could be eventually be lost in the worst case scenario, which has played out in Denmark already. “We already have lots that are mortally wounded,” Thomas said.



Ash dieback will be virtually impossible to eradicate from the UK, Thomas said, as its spores can be blown more than 10 miles in the wind and survive on woodland floors for four or five years.

However, ash trees have a very wide genetic diversity and some are resistant to the fungus. Three genetic markers have already been identified and will be used to select trees for future planting efforts. The genes that give the special strains their resistance could also be inserted into trees via genetic engineering, Thomas said.

A spokeswoman for the Department of Environment, Food and Rural Affairs (Defra), said: “Natural tolerance to the disease exists and the UK is leading the way on work to identify resistant strains, investing more than £21m in tree health research. Our approach also includes protecting non-infected areas and managing infected trees.”

Defra has identified the emerald ash borer as a “significant threat” and worked with other EU nations to introduce restrictions to protect against its spread. Imports of ash trees have been suspended since ash dieback was first recorded in the UK.

Facebook Twitter Pinterest The larvae of emerald beetle feed on the inner bark of ash trees, disrupting the tree’s ability to transport water and nutrients. The beetle killed about 10 million ash trees in Michigan, Ohio and Indiana in 2003. Photograph: Sipa Press/REX/Shutterstock

“If the ash went, the British countryside would never look the same again,” Thomas said. Beyond the loss of the trees themselves, the species is associated with over 1,000 species of animals, birds and plants. In particular, over a 100 species of lichens, fungi and insects would decline or become extinct if the ash was gone.

Ash had been thriving in Europe until recently thanks, paradoxically, to air pollution: nitrogen pollution has acted as a fertiliser. Climate change has also aided ash because it is sensitive to spring frosts and therefore benefits from warmer springs.

Thomas said, while it may well be too late to save most ash trees, more could have been done sooner: “It beggars belief that we had known this disease was coming for decades but we didn’t do anything about it.”