Book excerpt: Alien species (weeds and pest animals) are acknowledged as the second greatest cause of biodiversity decline, after habitat loss. Despite this, there is a lack of information on the biodiversity at risk from alien species. This lack has hampered effective management of invasive species at all levels from government policy to on-ground control. Given that the number of new introductions of alien species has increased dramatically over the past century, it is imperative that proper information on their impacts be compiled and disseminated.