Drought risk in Scottish forests

Drought, as a significant risk to Scottish forests, is likely to be exacerbated by the changing climate. This report summarises the current state of research, describes ongoing projects and identifies knowledge gaps and potential research directions. Considerations around the policy and practice implications are made, taking into account the available information.

Key findings

• There is high confidence that especially in east, central, and south Scotland the direct effects of severe droughts are likely to be felt primarily in forest productivity and carbon sequestration. 
• Tree species are known to differ in their vulnerability to drought impacts. The productivity of Scots pine, Douglas fir, and Sitka spruce can be heavily impacted by severe droughts. Trials of different species provenances have shown that there can be as large a variation in drought susceptibility between provenances as between species.
• Drought effects are the result of the complex interplay between climate extremes, many different components of forest ecosystems and other biotic and abiotic disturbances. All these elements will be affected by climate change in ways that cannot be confidently projected, which makes predicting the interactions between them even more difficult.
• There is medium confidence that applying dendrochronology (the study of annual growth increments, or tree rings) alongside remote sensing and drought indices could help understanding of the risk of large-scale drought impacts.