April - colonisers
Many species are already responding to climate change by expanding their distribution across Scotland as conditions become more favourable.
Northward shifts in species’ ranges have already been observed for some mammals, fish, plants, spiders, butterflies, intertidal snails and barnacles. Butterflies are a particularly good group to use as indicators of climate change. They are easily recognisable, are attractive and generate a lot of public support and involvement. A survey in 2007 based on sightings from members of the public found that the orange-tip butterfly has extended its range since 1997 both northwards and westwards, with many new sites in Wester Ross and Sutherland in particular.
Such expansions of native species indicate changing conditions and are largely to be welcomed, posing little threat to other native animals and plants.
Other colonisers, however, are less welcome: the invasive non-native species. There is a growing list of species that have been introduced into Scotland. Some were introduced intentionally, whilst others have arrived by accident via ship ballast or as stowaways. With changing conditions, increasing numbers of these species are finding conditions more amenable to their survival and spread at the expense of native species which are unable to compete. We need to improve our understanding of how to adapt our management to control the threats posed by these new invaders, and to reduce the impacts on our native species in a changing climate.
