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Future performance of current stands

Forestry Commission England is working to increase the adaptive capacity of the woodlands we manage to be resilient to the future climate on the basis of the High emissions scenarios in the middle of the century. We anticipate that by taking this approach to woodland management we will maintain a position on a trajectory of change that allows us to adapt our woodlands to whatever happens beyond 2050.

Forest Research has assessed the performance of our current species (and some provenances) on our estate, to indicate changes in suitability that would be expected in the absence of adaptation. The analysis was undertaken using ESC, based on species distribution from the sub-compartment data base and 1:250,000 scale soil association maps. 

The outputs therefore can only be indicative, providing a visual projection of the direction and extent of future impacts on forests in the absence of adaptation.

The legend describes species in terms of suitability based partly on an expectation of yield performance, but also on expert knowledge of the ability of the species to produce viable seed. Suitability classes include:

Very suitable = more than 70% of the maximum yield of the species in Britain                                                                               Suitable        = between 70% and 50% of the maximum yield     Marginal        = between 50% and 30% of of the maximum yield  Unsuitable     = less than 30% of the maximum yield in Britain

When looking at the outputs it should be noted that 2050 is less than a rotation away for most conifers, and that 2080 is within the rotation of most broadleaf species. 

 

Changes in productivity.

The same data sets as for performance, have been used to explore the impact on future productivity. The same caveats of caution must be considered when examining the detail.

Productivity is measured as average yield class

Implications for the Trees and woodland on the Public forest estate

By the middle of the century, under a High emissions scenario, there is a risk that slightly more than 20% of the PFE would be Unsuitable or Marginal (in terms of commercial timber production) should these more extreme climate scenarios be realised and in the absence of adaptation. Of this area, only 5% would be deemed Unsuitable, although it should be noted that the Marginal category assumes that attitudes to acceptable levels of productivity by forest managers adapt to changing conditions. For both conifers and broadleaves, more than 75% of the PFE would remain as either Suitable or Very Suitable under the relatively extreme climate change scenarios assessed here.

For conifer stands, the implications are that even in the absence of adaptation when restocking at the current time, there is a likelihood that those stands would remain suitable through the majority of the current rotation (~40-60 years, depending on species). However, any delay in implementing adaptation measures with respect to species choice would increase the proportion of crops subject to the risk for the latter half of the century (i.e. 2080s). For broadleaf species, a risk assessment for the middle of the century should not be considered in isolation as a significant proportion of its rotation (generally >100 years) would be beyond this time-frame.

The relatively benign risk assessment for the middle of the century (i.e. 2050s) is replaced by a much more serious picture towards the end of the century. Across the PFE, only 38% of stands would be considered Suitable or Very Suitable under current definitions. The situation for conifers is particularly worrying, with 32% of stands classified as Unsuitable in this analysis. In contrast, only 11% of broadleaf stands would be defined as Unsuitable, with the majority (58%) assessed as Marginal.

In terms of productivity, when these figures are aggregated across the whole of the Public Forest Estate, there is a risk that productivity (or yield class) could decline by 7% by the 2050s and by 35% by the 2080s, in the absence of adaptation. The implications are more serious for broadleaf woodland for which there is a risk of a 49% decline in productivity by the 2080s (15% by the 2050s), reflecting the larger proportion of broadleaf woodland on the PFE inthose regions where the climate projections indicate more serious summer droughts are likely. For the main productive conifer species, there is a risk that productivity could decline by 32% by the 2080s (5% by the 2050s).

The negative impact on yield is more significant in the south and east of England compared to the north and west.

Sitka spruce on the Forestry Commission estate in England

This analysis by Forest Research uses sub-compartment shape files from our Forester GIS. Soils data is at a very low resolution. The analysis assumes restocking using the same provenance. Sitka spruce is a coastal species requiring moist oceanic climatic conditions. The map demonstrates the need to be seeking to use more drought tolerant species during the next decade. This is most apparent in the east and south of England.

Last updated: 2nd December 2014