Forest pests in 21st century Britain: a review of impacts and management

Threats to trees and forests from insect pests are increasing as a result of the globalization of trade and climate change. Impacts are greatest when insects attack hosts lacking evolutionary resistance. Preventing the establishment of new, non-native forest pests—defined here as insect species posing economic or ecological risks to trees—and reducing damage from existing ones is essential for sustaining forest ecosystem services, including timber production, carbon sequestration, and biodiversity. This study provides a comprehensive assessment of forest pests in Britain, identifying 56 pest species of concern. Fifteen are native, while the remainder originate from mainland Europe (27), Asia (10), North America (9), and Australia (1). A structured scoring system showed pest pressure continues to rise through increasing detections, but more recently detected pests are not necessarily more damaging than those detected earlier. Key drivers of pest establishment and impact included trade, climate, and tree stress. Forest management acted as both a driver of pest problems and a mitigator of damage. Pine, spruce, and oak experienced the greatest pest pressures. Two beetles—the native large pine weevil and the non-native great spruce bark beetle—were classified as having very high impact. Ten additional pests were rated high impact affecting both conifer and broadleaf hosts under varied management regimes. Most species (44) were scored as low to medium impact under current conditions, although several have caused substantial damage historically, in other regions, or under different environmental or management conditions. Native and non-native species occurred across all impact categories. Only 4 pests were intensively managed, and 7 routinely managed; the remaining 45 species received minimal or no management effort. Five species were identified as potentially under-managed relative to their impacts, highlighting opportunities to better align management effort. Overall, forest pest management in Britain only partially aligned with Integrated Pest Management (IPM) and Sustainable Forest Management principles, relying heavily instead on natural regulation. This emphasizes the need to embed core IPM practices to prevent further pest establishment, reduce damage, and strengthen long-term forest resilience under future environmental changes.