Indicators and trends: Suitability and productivity (forestry)

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

SCCAP objectives:
N1: Understand the effects of climate change and their impacts on natural environment
N2: Support a healthy and diverse natural environment with capacity to adapt
N3: Sustain and enhance the benefits, goods and services that the natural environment provides

How is changing climate suitability affecting the productivity and sustainability of Scotland’s forestry?

Climate change is expected to bring both risks and opportunities to Scotland’s productive forestry.

The projected warmer climate will increase tree growth generally across the country (though there will be significant regional variability) with a resulting increase in productivity in areas not limited by water and available nutrients. This increase will also potentially aid the target of Forestry Commission Scotland (FCS) to increase the country’s woodland by an additional 100,000ha between 2012 and 2022. This would significantly contribute to Scotland’s emission reduction targets by locking up carbon in the growing trees. New woodland areas also bring wider environmental benefits and if spatially targeted within habitat networks will reduce habitat fragmentation.

Whilst a wider selection of species will be able to grow, particularly favouring high quality broadleaved trees in the South, the climatic changes will also alter the suitability of sites for species of trees already growing commercially in Scotland which could impact both positively and negatively on the productivity and sustainability of the forestry sector.

Changes in the seasonable distribution of rainfall are projected to increase the risk of drought in summer with a resulting decrease in suitability for species more sensitive to water limitations (e.g. Sitka spruce). Increased winter rainfall and a greater frequency of intense rainfall events will decrease the stability of slopes in some areas.

Milder winters and warmer wetter springs are likely to favour the abundance and distribution of over-wintering pests and diseases, and damage or stress resulting from drought, temperature extremes or storm damage will increase susceptibility to these pathogens.

An increase in periods of drought will heighten the threat to Scotland’s forests from wildfires. Though typically in Scotland the main damage from such events is to the understorey, even if tree mortality does not occur, fire damaged surviving trees are more susceptible to subsequent attack by pathogens or other stressors.

Wind throw can cause significant damage through uprooting and snapping of stems. Though there is still a high degree of uncertainty surrounding the projected impact of climate change on high winds and storm events in Scotland, it is known that forest stands in wetter soils are at greater risk from high winds. Furthermore, the projected increase in growth rate may mean forest stands reaching a height which puts them at risk at a younger age.