Oak trees have long had a reputation for supporting a range of biodiversity, however, research published on 15 April has uncovered just how many species depend on British oak to survive. The decline of these iconic trees, currently threatened by pests, diseases and climate change, could put a total of 2,300 species at risk.
A £1.25m study called ‘Protecting Oak Ecosystems’ has produced what is said to be the most comprehensive list yet of all species known to use native oak trees. The 2,300 total species are made up of invertebrates, birds, mammals and fungi, to name just a few. This figure does not include any of the bacteria and other micro-organisms that are associated with oak so the real number, although unknown, is likely to be much greater.
Lead author Dr Ruth Mitchell, of the James Hutton Institute’s Ecological Sciences group, said: “Our really old large oak trees support the greatest number of species. We are currently benefiting from trees established hundreds of years ago.
“We hope that this work will help us start thinking now about how our woodlands could look in hundreds of years and the biodiversity they might support.”
The project found of the total number of species affected, 326 were completely dependent on oak, with 229 being highly reliant on the tree. Examples of such species included the moth oak lutestring, fungi oak polypore and the beetle oak leaf-roller. These 555 species were considered most at risk from a decline in oak health.
Although currently at risk from a range of pests and pathogens including acute oak decline, chronic oak decline, oak processionary moth and powdery mildews, a significant loss of oak is not predicted imminently. However, oak is predicted to decline in some areas of the UK in the long term. This led the project to assess other tree species for their suitability for supporting the biodiversity associated with oak. Ash trees were identified as the tree that supported the greatest number of oak associated species. Unfortunately, ash trees in the UK are already declining due to ash dieback, caused by an introduced fungus.
In total 30 other tree species were assessed for their suitability; the findings are being made available to woodland managers to help them identify other tree species that could also support oak biodiversity. The study found that increasing the diversity of native tree species in our woodlands is vital to support future biodiversity.
Lord Gardiner, Defra Biosecurity Minister, said: “I welcome this publication which highlights the importance of addressing the serious threats to our oak trees which would also affect a great number of species that are dependent on them.
“What we learn 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.”
The work has been published in the journal Biological Conservation and is available at https://doi.org/10.1016/j.biocon.2019.03.040.
