Newly published State of the UK’s Oaks report outlines risks to UK oak trees

Oaks are a keystone tree species, underpinning ecosystems, storing an estimated 31 million tonnes of carbon, and delivering around £0.7 billion a year in environmental, social and economic benefits.

They support more biodiversity than any other native tree in the UK, with more than 2,300 species recorded as being associated with them, including 326 species that depend entirely on oak for survival.

A new Defra funded report published today by Action Oak, ‘The State of UK Oaks’, highlights that the UK’s iconic oak trees are experiencing a combination of pressures, with scientists noting that, without ongoing action, oak could become less prominent in the UK’s landscape.

Experts note that safeguarding UK oak trees is important, observing early patterns that have also been seen in other UK tree species. They describe the situation as a gradual ecological challenge, with early indicators similar to those that preceded issues such as Dutch elm disease and ash dieback.

The report sets out the current state of UK oaks by bringing together key information, monitoring data and a review of existing work, while identifying important evidence gaps, and is structured in three parts: 1) an overview of the importance of oak trees in the UK; 2) an assessment of the main threats currently affecting them; and 3) an examination of their extent, condition and genetic diversity, with key evidence gaps highlighted at the end of the report.

Selected points from the report

Ancient and veteran oaks are particularly important, providing habitats that have taken centuries to develop for rare fungi, beetles, lichens and insects that cannot survive elsewhere. Losing oak trees could trigger cascading biodiversity loss, impacting ecosystems that have taken centuries to develop.

Fragmentation of oak landscapes is important for maintaining oak health. Without connected networks of oak trees across the countryside, even species that survive locally may struggle to move, adapt or recover in a changing climate.

One example of a threat to UK oaks is Acute Oak Decline, a fast-acting condition, has now been confirmed at 394 sites across the UK (as of 2023). The disease is driven by a complex interaction between bacterial infections and the two-spotted oak buprestid beetle, exploiting trees already weakened by drought, soil damage and environmental stress.

Climate change is amplifying these threats. Oaks are now flushing their leaves 10 to 16 days earlier than they did at the start of the century, while hotter, drier summers are increasing drought stress, particularly in southern and eastern England. Scientists stress that while native oak species may appear resilient at a continental scale, individual trees and fragmented woodlands are more vulnerable when multiple pressures combine.

Annabel Narayanan, Director, Action Oak: “The report’s findings are a stark warning. What we are seeing with oak is not a single threat, but a convergence of pressures acting at the same time. Ageing trees, failed regeneration, climate stress, pests and disease. Each one on its own might be manageable, but together they are pushing the UK’s most important tree towards a tipping point, this could be a slow-burn- ecological disaster.”

Geraint Richards, Head Forester to the King and Duchy of Cornwall: “Oak supports more biodiversity than any other native tree in Britain and stores around 31 million tonnes of carbon. When a species that underpins ecosystems, climate resilience and cultural identity starts to fail, the consequences are national, not local. Long term surveys show fewer young oaks establishing, while mature trees dominate the landscape. Without regeneration, today’s ageing oak population becomes tomorrow’s ecological cliff edge.”

Professor Nicola Spence, UK Chief Plant Health Officer, Defra: “Oak trees are a cornerstone of the UK’s landscapes, supporting a wide range of species and enriching our cultural and natural heritage. Yet our native oaks are increasingly under pressure, including from Acute Oak Decline – a complex and serious condition that threatens the long-term resilience of this iconic species.”

“The ‘State of the UK’s Oaks’ provides an important evidence base to help us understand these challenges and focus our collective efforts to ensure that future generations continue to enjoy the immense environmental and societal benefits that healthy oak trees bring.”

Experts involved in the report emphasise that the issue is pressing, noting that signs of decline are already evident rather than a distant concern. They highlight the need for coordinated national efforts to protect existing ancient oaks, support natural regeneration, manage pest and disease pressure and monitoring, and improve landscape connectivity to help oak populations adapt to a changing climate. We need a national effort to protect ancient oaks, restore regeneration, tackle disease, and build resilient oak landscapes for the future. That means action from government, landowners, planners, conservationists and the public, all working together. The issue is already emerging, and taking action now will be important to safeguard the oak.

Future Trees Trust

Future Trees Trust is directly addressing several of the challenges highlighted in the new State of the UK’s Oaks report. Our long-term research focuses on improving the genetic resilience, health and productivity of both pedunculate and sessile oak. We run the UK’s first tested oak seed orchards which will provide high quality, reliable planting stock for future woodlands. Our breeding and progeny trials support better understanding of adaptation to pests, diseases and climate stress. Through the Best Practice Prescriptions for Quercus robur and our work with seed suppliers and nurseries, we are helping to increase the availability of superior UK grown seed and improving establishment success. These programmes ensure that the next generation of oak is better adapted, better sourced and better supported, contributing practical solutions at a national scale.