The end of summer and beginning of autumn is one of the best times of year to get out into our woodlands – havens for wildlife and stunningly beautiful in the changing seasons. For hundreds of years our woodlands have been our providers, protectors and sanctuaries; but for the last ten years or so, our woodlands have been waging a war of their own.
Ash dieback, caused by fungus Hymenoscyphus fraxineus, is ravaging our woodlands and causing the deaths of millions of our native ash trees, which are more commonly found on limestone and chalk landscapes. It is spore driven and travels in the wind for miles, so there’s been little to no means of stopping the spread since it was first discovered in the UK in 2012. Eleven years on, and the true impact of ash dieback is starting to reveal itself.
All over the country our ash is looking very poorly, with dead branches high in the canopy, a blackening of leaves, discoloured stems and diamond shaped lesions on the trunk. The fungus kills off the canopy of the ash tree, preventing the tree from building energy from the leaves to grow, which causes the timber to become very brittle. As a result, an infected tree is unlikely to fall like a traditional felled tree but instead can lose large limbs or fall entirely without warning. Once the trees die back completely – usually within a few months in young trees and often horrifyingly quick in mature trees – they become bare of all foliage before infections from other fungi, such as honey fungus, also cause them to drop limbs or collapse. Recent studies estimate that ash dieback could result in the loss of anywhere between 70% and 99% of ash trees in the UK, changing our woodland landscapes forever.
For Yorkshire Wildlife Trust, ash dieback has already had a significant effect. Just last month, the Trust closed Moorlands nature reserve near York so that they could safely fell several trees which had been killed by ash dieback and posed a safety risk due to their proximity to nearby paths. The Trust worked with specialist contractors and a tree harvesting machine, which safely dismantled and lowered the trees down.
Sadly, some Yorkshire nature reserves are particularly affected by ash dieback, including Ashberry, Chafer Wood and Grass Wood in North Yorkshire, and Brockadale and Hetchell Wood in West. Such work will now have to be an annual undertaking, as the disease unavoidably spreads to more of our reserves year on year.
Safely removing trees killed by ash dieback on reserves across Yorkshire costs Yorkshire Wildlife Trust thousands every year. There is no funding available to help mitigate the impact of ash dieback, which means increasing costs of safe removal as the disease spreads restrict the Trust from doing other important reserve work. The Woodland Trust estimates that the overall cost of ash dieback to society will be £15 billion.
Hope on the horizon
There is hope on the horizon. Initial findings estimate that 1-5% of trees may show reasonable tolerance to ash dieback, but none have been found to display complete resistance. The population could eventually recover over time.
Tolerance to the disease is complicated because a number of factors play into it including genetic traits, the health of the tree, its environment, and the number of ash dieback spores in the atmosphere. By studying and identifying the genome that supports the resistance, scientists hope to provide a new generation of ash that can be used to repopulate.
We also know that our woodlands can adapt and recover, as we have witnessed a similar mass death of a favourite tree before. Dutch elm disease decimated our native elm species in the 1960s and caused the death of millions of trees: an estimated 90% of the population. At the time, elms were a prominent tree in our woodlands and hedgerows, but other tree species (including ash) began to thrive in the space they left behind. Though the decimation of the ash tree population will be devastating to the species that entirely rely on it, wildlife that is able to adapt will have new tree populations to depend on. As in the 1960s, with dedication and care we will be able to save our woodlands.
Infected trees can also pose some benefit to woodland wildlife. Trees which are not considered a health and safety risk are left in place to help identify trees with natural resistance to dieback. These trees are also good for our woodlands, as they’ll provide excellent habitat for all sorts of wildlife in the form of the standing and fallen deadwood. Wood boring insects will take over these trees, which will then become hunting grounds for woodpeckers. Other birds, bats and small mammals will also use them for shelter, roosting and nestbuilding. Native fungi, such as the vivid scarlet elf cup, will colonise here, as shall mosses and lichens. Eventually, dead and decaying material will slowly seep its nutrients back into the soil, feeding the growth of more plant life, including the new saplings that will take the ash tree’s place in the canopy.
Yorkshire Wildlife Trust is helping our woodlands to heal however we can with hope for a more verdant future. Help to support our reserves work by joining our 45,000-strong membership community or with a donation. ywt.org.uk.
