Science & Environment

Denmark's ash disease dieback toll poses warning to UK

Ash tree
Image caption "The tree of life" has an elevated position in Denmark

The UK's 80 million ash trees are under threat from the spread of ash dieback disease. And experts may not find much comfort from Denmark, where they have been struggling against the fungal infection for a decade.

The humble ash tree has always enjoyed an elevated position in Denmark. Generations of school kids have been told and retold that it is tree of life - essential to the health and welfare of this country's landscape and culture.

It is a story Moreton Kyelmann, a guide at the Danish Museum of Hunting and Forestry, regularly gives to pre-school children. These days he spares them some of the darker detail: "In Old Norse mythology, the tree of life is the most important thing of all. It connected everything.

"The legend is that when the ash tree dies, the world will fall as we know it. It will be the end of the Earth."

The sad fact for Denmark today is that the ash trees are disappearing. The Chalara fraxinea fungus which causes ash dieback was first discovered in Denmark in 2002.

By 2005 it had spread across the entire country. Today at least 95% of ash trees here are either dead, or dying because they have the disease.

'Financial disaster'

For foresters like Anders Grube, the disease is a management nightmare. Many of his ash trees have already been cut down - the timber worth a fraction of the price he was getting before the fungus arrived.

"It is a disaster. I am losing lots of trees and lots of money. In this forest I have lost about a million pounds," he says.

"Before this disease we were getting double the money for ash we are getting now. I am lucky I can sell to China, but I am only getting half the price."

Ash dieback also causes big problems for those who rely on a steady supply of ash wood.

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Media captionJeremy Cooke talks to a private forester about how ash dieback is affecting business

The PP Mobler workshop looks and feels like something from the 1950s. It's all handtools and smell of sawdust.

The high-end, hand-made furniture they make here relies on the strength, flexibility and colour of Danish ash. Manager Kasper Pedersen says there's enough in store for just three more years of production.

"We don't know the exact consequences yet. If it really comes to a point when all of the European ash forests disappear, then we really will have a hard time.

"It will be a great loss. It will be like losing something really valuable.... We can live without it, but it will be a great loss."

If the message from Denmark is bleak, there is also hope. A very few ash trees - maybe 2% - seem to be naturally resistant to the killer fungus.

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Media captionInside the greenhouse used to identify resistant strains

When such trees are identified, specialist tree climbers are despatched to climb 20m and higher into the canopy to collect the seeds. The idea is to conduct detailed, scientific trials to establish whether their apparent immunity is passed on to their offspring.

Prof Erik Kjaer, of the University of Copenhagen, warns that the experience in Denmark suggests that Britain too will find it impossible to halt the spread of the disease. Instead, the focus, he says, is on finding survivors with natural immunity to provide the ash trees of the future.

"It is a terrible disease and this is the only kind of optimism I can offer the UK - there seems to be some kind of resistance and maybe it can work. But of course this is based on a very pessimistic view that the vast majority of trees seem to be highly susceptible."

Back at the university's greenhouses and laboratories there is intense activity. Hundreds of metre-high saplings are being deliberately infected with the disease so scientists can watch how it develops, and establish which of the clones are genetically immune.

But PhD student Lea McKinney believes the real key to finding a cure lies deep in the heart of the nation's state forests.

"The idea is that we want to go and collect these individuals in the forest and then we will graft them and put them in new seed orchards and this will be used to make new trees for the future."

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