Oak and ash in retreat as UK hots up

Times Online - UK



From The Sunday Times
August 3, 2008
Oak and ash in retreat as UK hots up
Brendan Bourne and Jonathan Leake

Britain's woods and forests face their greatest disruption since the last Ice Age with native species such as oak, beech and ash under threat from climate change, according to research.

These and other native trees are likely to retreat from parts of the warmer south and west as well as East Anglia, leaving woodlands dominated by species adapted to heat and drought, such as Corsican pine, Spanish oak and shrubs including spindle and dogwood. Many of these species were introduced to Britain as ornamental trees but are now expected to flourish in the wild. American giant redwoods already grow well in England and could thrive.

Further threats are posed by disease. Half the country's 2m horse chestnut trees are suffering from bleeding canker, which disfigures the trunk and branches. Oak and beech trees are being hit by sudden oak death, a fungus carried by rhododendron bushes.

Research about the scale of the change will be presented to the British Ecological Society next month. “Climate change will have a [big] impact over the next five decades,” said Dr Keith Kirby, a woodland scientist with Natural England, who will present a study on conserving woodlands as the climate changes.

“Our woods will change. Many species will cope with some warming but there is uncertainty about what happens with extreme events such as droughts and storms, which we expect to become more frequent.”

Beech is particularly vulnerable to summer drought because of its shallow spreading roots.

Gill Stribley of Surrey Wildlife Trust has studied British beech trees for 19 years and recently noted a marked decline in their health and growth.

“What is of concern is how the old trees will be replaced. Younger ones are not doing well. Whether they reach maturity remains to be seen. Trees less than 50 years old are showing changes that we would not expect to see until they were about 140,” she said.

Researchers from the Forestry Commission have looked at the potential for change. They predict, for example, that the number of native oak and beech will decline sharply across the southeast by 2050.

Such change could have a marked impact on the Chilterns, Cotswolds, North Downs and South Downs.

James Morison, head of the commission’s environmental change group, said the differences could be subtle. Some native trees might, for example, be replaced by similar European species.

Scientists are cautious about making exact predictions about how the climate will alter, partly because there is uncertainty over how the global temperature rise of 2C-3C generally forecast by 2050 will affect Britain.

Some experts believe that Britain should protect its woodlands by planting varieties better able to cope.

“We need to look further afield for new species,” said Tony Kirkham, head of the arboretum at Kew Gardens, southwest London. “The right way to go is to plant different strains of our native trees, perhaps using seeds from France or Germany.”

Some woodlands are changing quickly. At the National Trust’s Kingston Lacy estate in Dorset, an avenue of beech trees planted in the 1830s is dying from successive dry summers and soaking winters and 150 have been felled.