New hope for Britain's ash trees

Ash trees, one of Britain’s most iconic and beloved trees, are showing signs of recovery after more than a decade of devastation caused by ash dieback — a disease that has spread rapidly and harmed forests across the UK. New scientific research offers a glimmer of hope that these trees may not be lost forever.

The disease, known as ash dieback, first appeared in the UK in 2012. At the time, experts warned that it could wipe out up to 85% of all ash trees. The fungus behind the disease, Hymenoscyphus fraxineus, attacks the tree’s vascular system by entering through its leaves and then spreading to the bark and branches, cutting off water and nutrients. This leads to blackened, shriveled leaves, dieback of branches, and often the death of the whole tree.

Over the past decade, the disease has spread to almost every part of the UK. Whole woodlands have been affected, and many trees that once lined roads, paths, and gardens now stand dead or dying. Conservationists feared that ash trees might suffer the same fate as elm trees, which were nearly wiped out in the 1970s by Dutch elm disease.

But there is new reason for hope. Recent studies led by Professor Richard Buggs from the Royal Botanic Gardens, Kew, and Queen Mary University of London, have revealed that some ash trees are naturally developing resistance to ash dieback. These trees are not only surviving the infection but showing fewer signs of damage. This suggests that their genetic makeup is helping them resist the fungus more effectively.

“We’re seeing a hopeful turn in the story,” said Professor Buggs. “Some ash trees are fighting back. But this progress has come at a cost — many trees have already died.”

A Closer Look at Tree Genetics

The discovery comes from a long-term study in Surrey woodlands where researchers observed small changes in ash tree DNA over several years. These genetic shifts, or mutations, are helping younger trees become more resistant than their older counterparts. Evolutionary geneticist Professor Richard Nichols explained that the data shows thousands of genes playing a role in helping the trees defend themselves.

“This is a rare chance to observe evolution happening in real time,” he said. “Although it’s been a tragedy for the trees, it has given us insight into how species adapt to new threats.”

This kind of natural selection — where trees with stronger disease resistance survive and pass on their genes — is a key process in evolutionary biology. In nature, species often respond to challenges like disease or environmental stress by slowly adapting over generations. In the case of ash trees, the process seems to be underway.

How the Disease Reached Britain

Ash dieback is not native to the UK. The fungus Hymenoscyphus fraxineus originated in East Asia, where local ash species co-evolved with the fungus and developed natural defenses. However, European ash trees had no such resistance. The disease likely arrived in Europe around 30 years ago, probably through the import of infected plants or timber. Once in the wild, it spread quickly through airborne spores.

This is not the first time that invasive species have caused havoc in native ecosystems. Dutch elm disease, sudden oak death, and the emerald ash borer in North America are all examples of how global trade can unintentionally introduce deadly threats to trees and wildlife. These examples highlight the growing importance of biosecurity — the measures taken to prevent the spread of harmful organisms across borders.

Supporting the Trees’ Recovery

While the discovery of natural resistance is good news, scientists say that ash trees still need help. Professor Buggs emphasized that we must protect young saplings from other threats, such as deer grazing, which can damage or kill recovering trees. He also supports planting programs that select and breed the most resilient ash trees for the future.

“We now have more reason to care for ash trees,” he told the BBC. “We need to protect them from deer and let nature help evolve trees that are better equipped to survive.”

Rebecca Gosling of the Woodland Trust agrees. She says this research underlines the importance of allowing woodlands to regenerate naturally and of learning how to best manage these precious ecosystems. “Ash dieback shows just how dangerous new diseases can be — not only for the trees themselves but for the animals and plants that depend on them.”

Ash trees support over 1,000 species of wildlife, from insects and lichens to birds and bats. If ash trees were lost entirely, the effects on British biodiversity would be severe.

A Cautious but Encouraging Outlook

Scientists are still cautious in their outlook. The road to recovery will be long, and many trees are still vulnerable. But thanks to a combination of natural evolution and careful human support, Britain’s ash trees may yet have a future.

The research findings were published in the journal Science, adding important knowledge to the growing field of forest ecology and plant genetics.

For now, these resilient trees offer a sign of nature’s strength — and a reminder of our role in helping protect it.