Ash "will go the same way as elm", largest ever study concludes

Twin threats to ash will "all but wipe out" the tree in Europe, according to what is claimed to be the largest-ever survey of the species.

Its author, Keele University reader in plant ecology Dr Peter Thomas, said: "Between the fungal disease ash dieback and a bright green beetle called 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."

Like ash dieback, caused by the fungus Hymenoscyphus fraxineus, the emerald ash borer (Agrilus planipennis) is native to Asia. It was accidentally introduced to North America in 2002, where it has killed millions of ash trees. Recorded in Moscow in 2003, it is spreading west and is believed to have reached Sweden. The adult beetles feed on ash leaves and do little damage, but the larvae bore under the bark and into the wood, killing the tree.

"Our European ash is very susceptible to the beetle," Thomas said. "It is only a matter of time before it spreads across the rest of the Europe, including Britain. The beetle is set to become the biggest threat faced by ash in Europe, potentially far more serious than ash dieback."

Assessments of the likely impact of ash dieback in Britain put the worst-case scenario at 95 per cent mortality. Recent research suggests that some ash clones are resistant to ash dieback, offering hope that breeding programmes could produce trees able to survive the fungus. But such resistance will not protect trees against the borer if it reaches Britain.

The loss of ash would change our countryside and our biodiversity. More than 1,000 species are associated with ash or ash woodland including 12 birds, 55 mammals, 78 vascular plants, 58 bryophytes, 68 fungi, 239 invertebrates and 548 lichen species, many of which are threatened or endangered and likely to decline in number and potentially become locally extinct.

"If the ash went, the British countryside would never look the same again," Thomas said.

His study is published this week in the Journal of Ecology.

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