There have been many well-publicized cases of invasive species of plants and animals, often introduced unintentionally but sometimes on purpose, causing widespread ecological havoc. Examples of such alien invasions include pernicious weeds such as Japanese knotweed, an introduced garden ornamental which can grow through concrete, the water hyacinth which has choked tropical waterways, and many introduced animals which have out-competed and displaced local fauna.

This book addresses the broader context of invasive and exotic species, in terms of the perceived threats and...