Biggest cost of tree disease will be loss of benefits such as clean air and water, study finds

An invasive fungal disease killing ash trees will cost the British economy nearly £15bn, a study has found.

Ash dieback, which is lethal to European ash trees, originated in Asia and is thought to have been brought to the UK on imported ash trees some years before it was first identified in Britain in 2012.

Now experts have calculated a multibillion-pound bill for the disease, with the costs expected to be more than £7bn in the next 10 years alone.

The biggest amount will be from the loss of benefits that woods and trees provide, such as clean air and water and storing carbon dioxide, according to the study published in the journal Current Biology.

Clean-up costs, such as felling dangerous trees on roadsides, railway lines and in towns and cities, would be about £4.8bn, researchers from the University of Oxford, Fera Science, Sylva Foundation and the Woodland Trust said.

Much of that burden will fall on local authorities, with the worst hit, Devon county council, expected to have to spend more than £30m a year on roadside ash trees, vastly more than the average council’s tree budget.

There will also be costs of replanting and research, and loss of profits for the forestry sector. The total bill is estimated to come in at £14.8bn over 100 years, with half of that, £7.6bn, falling within a decade.

The researchers said there were 47 other tree pests and diseases that risked costing £1bn or more if they became established in Britain. They have called for a nationwide replanting scheme, which they said could reduce the cost of ash dieback by £2.5bn by ensuring that lost benefits are replaced.

A greater focus on, and investment in, biosecurity and sourcing of safe plant material was needed to keep new diseases out, they warn. Far tighter controls on imports of live plants should be introduced, as this is the way most tree diseases come into the country.

The bill for dealing with ash dieback, which is expected to kill 95% to 99% of native ash trees, dwarfs the annual value of the import and export trade in live plants to and from Britain, which was about £300m in 2017.

Dr Louise Hill from the University of Oxford, the lead author of the study, said the number of invasive tree pests and diseases was increasingly rapidly, mostly through human activities such as plant trade and climate change.

“Nobody has estimated the total cost of a tree disease before and we were quite shocked at the magnitude of the cost to society,” she said. “We estimate the total may be £15bn; that’s a third more than the reported cost of the foot-and-mouth disease outbreak in 2001.”

Dr Nick Atkinson, the senior conservation adviser for the Woodland Trust and co-author of the paper, said: “When ash dieback first entered the country, no one could have fully predicted the devastating impact it would have on our native habitats. To see how this has also affected our economy speaks volumes for how important tree health is, and that it needs to be taken very seriously.”

