One of the inevitable consequences of climate change is there are now many more species on the move, even without human assistance. Thus in Britain, new species arrive from Europe continually, and gardeners with an interest in wildlife are often among the first to notice.
Colonisation can be a gradual process. New species of mobile animals, such as moths and bees, arrive here all the time, but it’s only when they establish a permanent breeding population that we decide to call them new residents. But how well do we know what was here
