Climate change and the future for broadleaved tree species in Britain

The most recent climate change predictions for the UK indicate a warming of between 2 and 5 degrees C by the end of this century, with drier summers and wetter winters also anticipated across the majority of the country. Changes are predicted to be more extreme in the southern half of the UK, where severe summer droughts will become commonplace. Although rising atmospheric CO2 levels are likely to increase productivity through 'fertilizing' photosynthesis, water limitation in southern England is likely to lead to an overall reduction in growth and increase in drought-induced mortality. Incorporation of, the climate change scenarios within the GIS model Ecological Site Classification indicates that in isolation, the effects of climate change will result in significant changes in species suitability. Under current definitions the majority of native broadleaf species are predicted to become unsuitable for commercial timber production in southern England. Genetic variability in local native populations may enable a degree of adaptation. Existing trials of ash (Fraxinus excelsior L.) suggest that the best performing provenances are those from regions with a climate similar to that of the trial site. The selection of a provenance for climate change adaptation should be from a region with a current climate well matched to a planting site's predicted climate of the future. Climate matching analysis indicates that coastal areas of western France experience a climate similar to that predicted for southern England by 2050, while the more extreme scenarios predict climates better matched to the Mediterranean region at high elevation by the end of the century. The scale of climate change predictions indicates that, in southern England, native broadleaf species may be unsuitable for timber production on some soils. The planting of non-native species may need to be considered to maintain woodland cover and ensure a viable hardwood timber industry.