Adapting Scotland’s forests to climate change – findings and recommendations

Key findings

More frequent green-spruce aphid attacks may reduce growth in eastern and southern Scotland.
(Photo: Clive Carter)

• The expected warmer climate will improve tree growth nationally, but particularly in southern and eastern Scotland. Productivity will increase generally, and this could be by 2 to 4 cubic metres per hectare per year (m³/ha/yr) for conifers on sites where water and nutrients are not limiting.
• The climate of southern and eastern Scotland will be more favourable for growing high-quality broadleaved trees on suitable deep, fertile soils.
• Droughty soils in eastern Scotland will become unfavourable for Sitka spruce and other drought-sensitive species.
• Changes in the seasonal distribution of rainfall will cause more frequent summer drought and more frequent winter flooding.
• Changes in the frequency of extreme winds will cause more wind damage. However wind scenarios have a high uncertainty attached.
• Pest and disease ecology will change with the climate; for example, more frequent green-spruce aphid attacks may reduce growth in eastern and southern Scotland.
• Scotland’s aspiration to expand woodland from 17% to 25% by 2050 provides an opportunity to target reforestation within habitat networks. This will reduce woodland fragmentation and thereby help improve the resilience of woodland ecosystems to climate change.

Emerging recommendations

Forest nurseries in eastern Scotland will have to adapt to the drier summers, for example by using more irrigation.

• Low-impact silvicultural systems (LISS) and the use of mixtures could provide the basis for adaptation strategies.
• Where other management regimes are used, a wider range of species and a broader range of genetic material within a species will increase stand resilience in a changing climate.
• Acceptance of natural colonisation of woodlands of non-native tree species may be a valid adaptation strategy, but this must be reviewed where conservation is a major objective.
• Forest nurseries in eastern Scotland will have to adapt to the drier summers (for example by using more irrigation) and to wetter winters (for example by avoiding soil damage).
• Contingency plans need to provide an adequate response to increasing risks of catastrophic wind damage, fire, and pest or disease outbreaks.
• The upper wind exposure limit, defined in terms of the detailed aspect method of scoring (DAMS), for productive conifer plantations may need to be reduced.