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Climate change and woodlands

Changing woodlands

The predictions external site   for likely changes in future climate suggest that Scotland will become warmer but, although rainfall may decrease in summer, winters are likely to become wetter. The impact this will have on Scottish woodlands is uncertain:

A changing climate will favour some species - both native species and commercially grown tree species - in some areas, while making conditions worse for others. The general warming of the climate is likely to lead to suitable conditions for many species (including changes in the impact of competition from other species) moving northwards and uphill. Some species will move in response, but their rates of movement may differ, leading to changes in the composition of communities. Other species may be unable to move quickly enough to keep up with changes, and could end up dying out locally or nationally.

Drier summers may increase stress in species susceptible to drought (e.g. Sitka spruce external site ), especially in the east of Scotland, and could lead to declines in oceanic lower plants - although wetter winters might restrict the impact.

A warmer climate may encourage the spread of pests and pathogens currently more associated with the south of England, or cause existing problems to become more common. E.g. It seems likely that climate change is one reason for the sudden increase in impacts of red band needle blight external site since the late 1990s. This causes defoliation, resulting in poor growth and, in severe cases, death of the tree. Corsican pine was the first species in Britain to be severely affected; it is no longer being planted and existing crops are being felled. Impacts on Lodgepole pine are similar but Scots pine seems to be less susceptible so far.

The timing of seasonal events in plants (phenology external site ) is changing, e.g. between 1971 and 2000, spring and summer started 2.5 days earlier per decade. Over the same period, trees have been coming into leaf earlier. The pollen season starts on average 10 days earlier and is longer than 50 years ago. Events may also become desynchronised; butterflies may emerge before food-plants are grown, and birds' eggs may hatch before their insect food has emerged. 

Overall, it seems that we must be prepared for a more unpredictable climate and hence a somewhat chaotic response from our woodland ecosystems. Scottish Natural Heritage has produced further information on climate change generally , and on a woodland case-study specifically.

Carbon storage

Forests act as carbon sinks, soaking up CO2 from the atmosphere; unfortunately reducing CO2 levels isn't as simple as just planting more forests. Soils, especially peat, also contain vast quantities of carbon. Trees absorb water from wet soils, drying them out, and their roots break up the soil structure; speeding up decomposition, and giving off CO2. We don't yet fully understand for all soils whether the CO2 absorbed by trees is greater than the CO2 given off by soils so we need to be careful to avoid planting on soils where this might be the case.

Forestry Commission have recently published an major assessment external site of the potential of the UK's woodlands to mitigate and adapt to climate change.



Last updated on Monday 9th April 2012 at 14:36 PM. Click here to comment on this page