What can we do about a decline in Britain’s native oaks?27 February 2019
Britain’s symbolic oak trees might have to be replaced by other native UK tree species or European alternatives in response to threats including diseases, pests and climate change, scientists warn.
An ongoing research project, titled PuRpOsE: Protecting Oak Ecosystems, is looking at ways to combat risks facing the UK’s two native oaks – English oak (Quercus robur), and Cornish oak (Q. petraea). A changing climate is making them increasingly susceptible to diseases that leave them leafless and bleeding from their trunks, as well as to pests such as moths that can strip them bare.
The project includes work from researchers across a six institute consortium including University of Reading, Forest Research, The James Hutton Institute, Centre for Ecology & Hydrology, Stockholm Environment Institute at the University of York and University of Oxford. Recommendations being presented at a conference at the Royal Geographical Society in London today include managing sites to promote conditions for oak growth and encouraging native broadleaved tree regeneration.
Other recommended actions include stopping clearing forests of dead wood, to benefit the 935 species that live on dead wood (including many fungi and invertebrates which are themselves a source of food for other species), and encouraging establishment of both native oak and other native tree species, which have been shown to support some of the same biodiversity as found on oak. Such actions should increase the resilience of our UK oak woodland for the long term.
Professor Rob Jackson, biological scientist at the University of Reading, said: “Britain’s oak trees are part of its cultural landscape, but they could look very different in future. The oak is a key component of woodland ecosystems in the UK and so its decline would have a much wider impact on other species, like fungi, insects and even humans.
Humans have long been influential in the management of oak trees, as it was historically used for many activities including use for buildings, and charcoal production for metal smelting, thus it was planted widely. Now humans must take action to protect our oaks for future generations. There is no one-size-fits-all solution, so forest managers need support to face the specific challenges facing different forests and put in place long-term strategies.”
Pests and diseases currently threatening Britain’s native oak trees include acute oak decline, chronic oak decline, oak processionary moth and powdery mildews. These, compounded by climate change, can result in a decline in the health and appearance of oaks, affecting the appearance of forests. Some cause bleeding lesions on the trunks, mildew on the leaves and loss of leaves and branches.
American red oak (Quercus rubra), the Austrian oak (Q. cerris), ash (fraxinus) and sweet chestnut (Castanea sativa), are some of the species investigated as alternatives to oak. However, these also face issues such as an inability to support the same level of biodiversity, altering other ecosystem functions and vulnerability to other diseases or pests.
Oak trees have been found to support a much higher diversity of associated species than other tree species. More than 2,300 species have been identified as depending on oak trees, plus more than 18,000 root-associated fungi and 40,000 bacteria. Species that are dependent on oak include the moths oak lutestring, great oak beauty and oak nycteoline; the fungi oak polypore, oak leaf blister and oak mildew and the lichens Arthonia byssacea, Calicium adspersum, Sclerophora farinacea.
The researchers are continuing to identify which areas of Britain will be most affected by a decline in oak and help develop tailored, flexible solutions for forest managers in these different areas.
Defra Biosecurity Minister Lord Gardiner said: “I welcome today's Protecting Oak Ecosystems event to highlight the important work undertaken to address the serious threats to our iconic oak trees. It is inspirational to see so many people gathered together to discuss this critical issue.
“The learnings from this project will feed directly into our Action Oak initiative, a collaboration of charities, government, landowners and research institutions whose aim is to protect the UK’s 121 million oak trees from plant pests and diseases.”