Indicators and trends: Pests, diseases and invasive species (forestry)

Scottish Climate Change Adaptation Programme (SCCAP)  theme: Natural environment

SCCAP objectives:
N2: Support a healthy and diverse natural environment with capacity to adapt

How is climate change affecting the pests, diseases and invasive species which threaten Scotland’s forestry and woodland biodiversity?

Pests, diseases and invasive non-native species (INNS) have the potential to disrupt key ecosystem functions and cause significant economic damage. Milder winters and warmer, wetter springs are likely to increase the risk from some over-wintering pests and diseases as a result of increased activity, reduced winter mortality and the potential to complete more generations in a season, resulting in larger populations. Other effects may be more indirect and result from a reduction in ecosystem resilience and therefore increased susceptibility to pathogens due to damage or stress as a result of drought, temperature extremes or storms. Changes in average temperature and rainfall will also alter the distribution of some native woodland species, facilitate the establishment of INNS and increase the invasive tendency of some.

Whilst the climate response function of these organisms vary, and non-climatic drivers (e.g. deliberate or accidental introduction via human activities) are often more significant, there are a number of organisms where climate is seen to be a critical driver which are already causing considerable impact to Scotland’s economy and wildlife. Two of the most significant risks come from:

• Phytophthora ramorum– a fungus-like pathogen whose distribution and prevalence is to a large extent determined by climatic factors. It poses a particular threat to larch, one of Scotland’s most important timber species, causing significant damage and mortality to infected plants.
• Dothistroma needle blight- which has become the most significant disease affecting coniferous trees in the UK and poses a particular threat not only to Scotland’s commercial forestry but also to native Caledonian pinewoods. It is believed that an increase in intense rainfall episodes coupled with warmer springs may have optimised conditions for spore dispersal.