is likely to have been introduced to western Europe and North America in this manner. The brown tree snake (Boiga irregularis) which has had a devastating impact on the native bird population of Guam appears to have been introduced via the trafficking of military materials to and from the island following World War II. Solid wood packing material shipped from China is thought to have housed the Asian long-horned beetle (Anoplophora glabripennis) leading to an outbreak in the USA in 1996 which triggered emergency control measures. Thought now to have been eradicated from a number of locations in the USA, this highly damaging polyphagous beetle is an alert list species in many parts of the world, with new detections and interceptions an ongoing challenge. Invasive plants have beenwidely introduced to new regions in contaminated seed and through the horticultural trade. Britain, for example, has a rich history of invasive plant introductions, with the Victorians displaying a particular penchant for the exotic and weedy ornamental (see Japanese knotweed and Himalayan balsam).

Understanding the likelihood of establishment of a species introduced to a new region is fundamental to allowing an accurate assessment of the risk it may pose. A recent horizon scanning event conducted by the EU-funded project Reducing the Impact of Non-native Species in Europe (RINSE) analysed and ranked a registry of non-native species thought likely to pose a risk to regions of the UK, France, Belgium and the Netherlands. Environmental and socioeconomic factors were then used to produce heat maps displaying the potential distribution of alert