Since their introduction into Britain between 1876 and the 1920’s, grey squirrels have spread rapidly, gradually displacing the native red squirrel in most of England and Wales, and in central and south-east Scotland.
Grey squirrels are extremely destructive in woodlands, stripping bark from the main stem and branches of trees. Increasingly, wider impacts of grey squirrels are being recognised as of potential major significance to woodland conservation, biodiversity and sustainability.
http://www.forestry.gov.uk/website/f...ue/INFD-69EKTZ