Climate change and UK woodlands

The impacts of climate change on UK woods and forests

Although one of the benefits of our woodland creation programme is the role they play in the fight against climate change, the trees themselves will be subject to a changing climate. The tree species that thrive in the UK have adapted to the climate and conditions that have arisen here since the end of the last Ice Age, around 10,000 years ago, but there are signs that those conditions are changing. Climate change scenarios predict that the UK is likely to become milder and wetter in the winter and significantly hotter and drier in the summer over the next century, and this will undoubtedly have an impact on trees and woodlands. Predicting the exact outcomes is difficult – this is a complex area with many factors affecting one another – but below is a summary of the sorts of effects we may see in the future.

Increase in atmospheric CO2
Possible benefits:
•    CO2 is a tree’s oxygen and therefore one of the consequences of its increase may be faster growth rates
•    We would also expect to see trees use water more efficiently

Possible negative effects:
•    An increase in leaf size meaning higher wind resistance (and a greater threat of being blown over), and a possible reduction in sunlight reaching ground vegetation
•    There could be a reduction in timber quality

Increases in temperature
Possible benefits:
•    Longer growing seasons
•    Lower risk of winter cold and snow damage

Possible negative effects:
•    Longer growing season reduces winter soil water recharging
•    Reduced winter deaths of pests and threats
•    Increased fecundity, due to warmth, of pests and threats

Changes to rainfall patterns
Possible negative effects:
•    Reduced tree stability in winter waterlogging
•    Summer drought mortality

What is being done to adapt to these changes?

Extensive research is being conducted by Forest Research, a part of the Forestry Commission, into the impact of climate change on trees and woodlands and what can be done to adapt to new conditions. A key basis for future planning and management is diversification, for example: broadening the choice of genetic material (including perhaps selecting stock from areas that are already adapted to the predicted conditions), mixing tree species in stands, and varying management systems and the timing of operations.

As trees take many decades to mature, foresters need to look much further into the future than other land-managers. To that end the Forestry Commission’s research is well disseminated amongst forest managers.

How does all this affect our carbon woodlands?

Carbon projections
The Woodland Carbon Code’s carbon projections are based on the Ecological Site Classification Decision Support System – developed and provided by the Forestry Commission and used by all forest managers (and by Forest Carbon). This tool is regularly updated by the Commission and reflects the latest modelling of the effects of climate change on the future growth of any given species in any chosen location. When we combine this data with the local knowledge of the forest manager at the project, we are able to be sure that we are making carbon capture projections based on the best available science.

Woodland design and management
Forest Carbon and its forest manager partners are also aware of the latest research about adapting to climate change, and using this and forest managers’ local knowledge about micro-climates, terrain and soil types we are able to plan our projects in the best way possible.

Forest Carbon research and development
Forest Carbon is working with the Future Trees Trust (FTT), whose aim is to improve the resilience of 7 key broadleaf species across the UK by introducing more genetic diversity, at our project at Iscoed.