NF1 Proportion of major timber species on Scotland’s National Forest Estate planted in areas likely to be climatically suitable in 2050 (Sitka spruce and Scots pine)

As the climate changes, so too will the suitability of sites for growing particular timber species.  Areas currently suitable for a certain species could become unsuitable over the next 40 years and beyond due to climate change. This could have impacts on forest productivity and therefore on the sustainability of Scotland’s forest industry. Moreover, areas currently unsuitable for a species could become suitable, presenting an opportunity for increased tree growth and productivity.

This indicator measures the change in the suitability of existing forest area managed by Forestry Commission Scotland, according to the UKCP02 Climate Projections High and Low emissions scenarios for 2050. It uses the Ecological Site Classification method (ESC), which classifies a site as ‘Very suitable’, ‘Suitable’ or ‘Unsuitable’.  It reports the change in suitability class by proportion of forest area by planting decade, for the key timber species Sitka spruce and Scots pine.

In Scotland there are around 1,410,000 ha of forests (18% of land area), of which approximately one third is managed by Forestry Commission Scotland (Forestry Commission, 2014). Detailed data for the location, management and species composition of individual stands is only available for the National Forest Estate, therefore this indicator considers only publically managed forest.

Timber production is an important provisioning service provided by Scotland’s forests, and timber production makes a significant contribution to Scotland’s economy through jobs in wood processing, forest management, timber haulage and associated industries. The direct Gross Value Added (GVA) of the growth and primary timber processing industry in Scotland is £1 billion (Scottish Forest and Timber Technologies, 2011). The total value of UK wood product exports in 2013 was £1.7 billion (Forestry Commission, 2014). Forestry Commission Scotland (FCS) aims to maximise the economic potential of Scotland’s timber resources, sustaining a predictable and stable supply of timber, while delivering a range of social, ecological and economic Ecosystem Services (Forestry Commission Scotland, 2013).

Related indicators:

NF6 Number of uses & users of the Ecological Site Classification (ESC) decision support tool

Suitability to baseline climate conditions

According to baseline climate conditions (1970-1990), the percentage of current Sitka spruce forest area planted on sites classified as suitable is 53%, as very suitable is 20% and as unsuitable is 25%.  For Scots pine at baseline conditions, the current percent of forest area planted on sites classified as suitable is 65%, as very suitable is 13%, and as unsuitable is 20%.

Suitability to 2050 climate projections

Sitka spruce

Under the UKCP02 high emissions scenario, in 2050 82% of Sitka spruce forest area will be classified as suitable or very suitable and 15% as unsuitable; under low emissions scenarios these figures are 81% and 15%.

The proportion of current Sitka spruce forest area projected to increase in suitability exceeds that projected to decline. For 2050 high and low emissions scenarios 11% and 10% respectively of forest area increase from unsuitable to suitable and a further 8% and 7% increase from suitable to very suitable. In contrast only 0.9% and 0.02% of forest area decline in classification from suitable to unsuitable, and 0% from very suitable to unsuitable.

The ESC classification of the majority of Sitka spruce forest area is projected to remain the same. For high and low emissions scenarios, 43% and 44% remain suitable, 18% and 19% remain very suitable, and 14% and 15% remain unsuitable.

Scots pine

Under 2050 high emissions scenarios, 80% of Scots pine forest area will be classified as suitable or very suitable in 2050 and 20% as unsuitable; under low scenarios these figures are 77% and 21%.

The proportion of current Scots pine forest area projected to increase in suitability exceeds that projected to decline. For 2050 projections (both high and low emissions scenarios), 1% of forest area increases from unsuitable to suitable, and a further 3% increase from suitable to very suitable. 0.6% and 1.2% forest area decline in classification from suitable to unsuitable and 0.4% and 0.7% decline from very suitable to unsuitable.

The ESC suitability classification of the majority of Scots pine forest area is projected to remain the same. For high and low emissions scenarios, 62% and 61% remain suitable, 12% (both scenarios) remain very suitable, and 19% remain unsuitable.

For both species, the differences between the 2050 high and low emissions scenarios are small.

Awareness of the impacts of climate change on species suitability is increasing, as is the use of decision support tools which provide species suitability under future climate projection, such as Ecological Site Classification (Forestry Commission, 2009). Changes to policy and best practice guides mean that plantings on sites classified as unsuitable in 2050 are likely to decrease.

This indicator only covers forests which form the National Forest Estate managed by Forestry Commission Scotland.  Privately owned woodlands are not included.  Around one third of Scotland’s forests are managed by Forestry Commission Scotland (Forestry Facts and Figures, 2014). Results for forests managed for timber production by the private sector are likely to be similar.

Suitability maps have been generated using UKCP02 projected climate data for 2050. No account has been taken of the impact of extreme events on tree species. Future analysis may be based on UKCP09 or 11-member RCM climate data. 2.5% of Sitka spruce forest area and 1.7% of Scots pine forest area lie outside the coverage area of the UKCP02 projected data.

Potential impacts of pests and pathogens are not included.

The accuracy of ESC is limited by the detail contained within the available soil maps for Scotland.

Kate Beauchamp, Forest Research, who completed the analysis underpinning this indicator. Philip Taylor, Forest Research, who calculated species suitability using UKCP02 data and ESC.