Professor Chris Thomas, a biologist from the University of York, is warning that labelling as non-native birds, butterflies and other species that move north because of global warming would create “one big headache”.
He points out that if Scotland becomes an independent country it will have to decide whether to classify thousands of species that only occur south of the border as alien. Other countries signed up to international agreements to protect wildlife have developed policies for non-native species.
But Thomas argues that it would be a bad idea to define English plants and animals as alien, and resist their arrival in Scotland. The rising temperatures caused by climate pollution are driving many species north, he says, and they should be welcomed.
Among the species that could cross the border is the Essex skipper butterfly, which is seen as an invasive species in North America. Historically a native of southern England, it has been spreading northwards and was recently seen in southern Yorkshire.