Warburg Nature Reserve is one of the gems of the Chiltern Hills. In autumn, its beech, birch and oak trees transform into a blazing canopy of red, yellow, brown and gold leaves. Buzzards and red kites swoop overhead, while an astonishing array of mushrooms – from milk caps to necklace earth stars – rise through the forest floor of the 100 hectare site.
However, this curtain of multicolored delights hides a dark secret. A walk around the reserve, which is owned by the Wildlife Trusts, reveals gaps that have recently appeared in the greenery.
Raw, white, leafless trunks tower over the paths, all victims of a devastating disease that is about to strip our forests bare and take millions of pounds from the budgets of wildlife charities: ash dieback.
The disease – caused by the fungus Hymenoscyphus fraxineus – first appeared in the UK a decade ago. At the time, experts warned that the ash die-off would have a bleak impact, although some hoped the resilience would spare some trees and leave parts of the forest relatively unaffected. Now, 10 years later, that prospect seems abandoned.
“We think we’ll be lucky if 5% of the nation’s ash trees survive this disaster,” said Debbie Lewis, head of ecology for the Berkshire, Buckinghamshire and Oxfordshire Wildlife Trust (BBOWT), which manages the Warburg Reserve .
Debbie Lewis, left, chief ecologist, and Steve Proud, director of land management, at Berks, Bucks & Oxon Wildlife Trust. Photo: Robin McKie/The Observer
“The loss of our ash trees is a tragedy in itself, but there are all kinds of side effects. Warburg is a popular reserve visited by thousands of people and this raises expensive health and safety issues,” she added.
The key problem for the Warburg – and for all the reserves managed by the 45 other wildlife trusts in the UK – is that more and more ash trees are dying and their huge rotting trunks are towering over paths and clearings. Many of them are in danger of falling and becoming a threat to visitors and workers.
“These dead trees are growing on slopes and near the right of way and are a hazard. So clearing them became a priority,” said Steve Proud, who is director of land management at BBOWT. “But this is a complex, expensive business that requires specialist intervention.
“Our trust has already had to spend £400,000 to pay for the clearing of the trees and we predict it has to pay a further £800,000 over the next few years. That’s a lot of money for a local wildlife trust and means we have a lot less money for wild habitat restoration – which is our main aim and goal.’
Ensuring that people are not harmed is not the only difficulty facing the Warburg Reserve, however. Many of its ash trees are home to bats – such as brown-eared bats and bats – and as these animals are protected by law, the trees must be carefully inspected to ensure they are not nesting in them. “Determining the tiny nest marks at the top of a 40-foot-tall tree is not easy, but it has to be done,” Lewis added. “And it all adds up to the work we now need to do to address the ash die-off.”
This thesis was supported by Rob Stoneman, director of landscape restoration for the Wildlife Trusts. “The impact of ash drying will be even greater than that of Dutch elm disease, which has killed millions of trees since it emerged in the 1970s. Our forests, especially in the north of England, are dominated by ash trees, so they will undergo very rapid changes over the next decade.
The brown long-eared bat relies on ash trees for nest construction. Photo: blickwinkel/Alamy
The consequences for some smaller trusts could be severe, Proud said. “We are a relatively large trust but the smaller ones have had to sell their assets and reduce education sessions to provide money to deal with ash die-off.
“We are facing huge costs over the next three to five years thanks to the disappearance of the ash, and this will come on the back of reduced income as inflation levels affect our members’ incomes.”
“There is a limit to which we can count on their generosity. So this threatens to become a perfect storm for us.”
The ash die-off is just part of a broader pattern of changes in our forests, Stoneman added. “In continental Europe, we are seeing an increase in a whole range of diseases, such as oak moth disease and pine blight. And that’s probably because trees are under stress from climate change.
“We’re getting hotter, drier summers and wetter winters, and that makes trees more susceptible to disease. Climate change is already having some really significant effects.
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