Expert Comment: Britain's woodland in perilMonday 29 October 2012
Dr Barbara Tigar, Lecturer in Biology at Hope, on a deadly new disease threatening the UK's ash tree population.
Long ago most of Britain was covered by deciduous woodland; think of Robin Hood in Sherwood Forest. Our remaining woodlands are valued for recreational activities, their wildlife, harvesting of wild foods and for traditional woodland industries such as firewood, charcoal making and timber extraction. Many woods are cared for by charities such as the Woodland Trust who aim to sustainably manage them whilst encouraging native wildlife and giving people access to enjoy these green and natural spaces.
The most abundant broadleaved trees in Britain are birch, oak and then ash and whilst they grow in woods, they are also common in hedges, parks and gardens. However, our trees are under threat from a new invader. Ash dieback, Chalara fraxinea, a disease that has been spreading across Europe killing trees has recently arrived on our shores. Anyone old enough to remember how Dutch elm disease changed our countryside from 1970s onwards will be alarmed to hear that this pathogen poses an even greater risk to trees. If ash trees disappeared this would have a negative impact on biodiversity, by reducing the quality of woodlands and urban areas as habitats for our native birds, mammals and invertebrates. In part of Britain ash is the dominant tree and the loss of large mature ash would leave huge gaps which would take many years to recover.
In February this year ash dieback was found for the first time in Britain. It was infecting saplings which had been imported from the Netherlands into a nursery in Buckinghamshire. In the following months it was found in Leicestershire, Renfrewshire, South Yorkshire and County Durham where imported ash trees were growing.
However, in October 2012 ash dieback was in the news because it was infecting trees in an East Anglian hedgerow far from any imported plants. Then on October 24th the Woodland Trust reported ash dieback infecting mature ancient woodland in Suffolk. Whilst the infected trees were removed and destroyed, these recent cases are of great concern because they occurred in rural areas and in some of woodlands of highest conservation value, the ancient woodlands.
The microscopic pathogens causing the disease may have spread via natural means on insects, the wind and rain, or were perhaps assisted by human activity to invade new areas. These new cases of infection suggest that everyone needs to be vigilant if we want to maintain our green and pleasant land.
FERA, the Department for Food Environment and Rural Affairs, are responsible for quarantine regulations and are treating ash dieback as a quarantine pest under national emergency measures. Anyone visiting woodlands can help by learning to identify ash trees and looking for characteristic symptoms of the disease on their bark and leaves which should be reported immediately. For Smart phone owners there is a free ap called Ashtag which was developed at the University of East Anglia to help you identify diseased trees, and from which you can submit photos and location information about any cases you have found. See: http://ashtag.org/