Biodiversity loss caused by invasive alien vertebrates

Abstract

The introduction of invasive alien vertebrates is a major cause of the loss of native biodiversity in many regions of the world. The threats posed by them are especially severe on oceanic islands and other isolated ecosystems, in which there are many examples of extinctions or declines of native species caused by alien vertebrates. Predatory mammals are the worst offenders, but mammalian herbivores can also cause biodiversity loss and may provide the prey base to support invasive predators. There are also some notorious examples of alien birds, reptiles and fish that threaten native biodiversity. The adverse effects of invasive alien vertebrates are illustrated by specific examples from New Zealand, including the multiple impacts of Australian brushtail possums (Trichosurus vulpecula). Invasive vertebrates can sometimes be eradicated in the early phases of establishment and can be removed from islands or other isolated areas. However, given the uncertainty about the effects of alien species, the best policy is to adopt the precautionary principle and avoid making introductions without prior rigorous assessment of the risks to native biodiversity.