extinction

We assessed the prevalence of alien species as a driver of recent extinctions in five major taxa (plants, amphibians, reptiles, birds and mammals), using data from the IUCN Red List. Our results show that alien species are the second most common threat associated with species that have gone completely extinct from these taxa since AD 1500. Aliens are the most common threat associated with extinctions in three of the five taxa analysed, and for vertebrate extinctions overall.

Only around a third of the world’s remaining forest cover survives in the form of Intact Forest Landscapes (IFL), and that proportion is declining.

Native plants and animals can rapidly become superabundant and dominate ecosystems, leading to claims that native species are no less likely than alien species to cause environmental damage.

Aerial baiting from helicopters with a bait-sowing bucket and GPS to ensure coverage with anticoagulant toxins in cereal-based baits can reliably eradicate rodents on islands. Current best practice for temperate islands is to bait in winter when the rodents are not breeding, rodent numbers are lowest so competition for toxic baits is lowest, natural food is likely to be scarce, and many non-target species are absent from the island. However, short winter day lengths at high latitudes restrict the time helicopters can fly and poor weather in winter may increase risks of failure.

The world is facing a biodiversity crisis. Nowhere is that more apparent than on oceanic islands where invasive species are a major threat for island biodiversity. Rats are one of the most detrimental of these and have been the target of numerous eradication programmes; a well-established conservation tool for island systems.

Invasive black rats (Rattus rattus) were successfully eradicated during 2012 from Pinzon Island in the Galapagos archipelago using the rodenticide brodifacoum. Potential exposure to brodifacoum in Pinzon tortoises (Chelonoidis ephippium), Pinzon lava lizards (Microlophus duncanensis) and Galapagos hawks (Buteo galapagoensis) was mitigated by captive holding of subpopulations. This was successful for all species during and shortly after baiting, however mortality of Galapagos hawks occurred post-release, likely due to the persistence of residual brodifacoum in lava lizards.

The Kuramoo, or Blue Lorikeet (Vini peruviana), is listed by IUCN as threatened. Formerly, the species was widespread on the Society and Tuamotu ISlands, but it became extinct on Tahiti, Moorea and other large islands in the Society Group early this century and is now also extinct on many other islands on which it once occurred. Today, in French Polynesia, it apparently survives only on two small islands in the Society Group and several in the Tuamotu Group.

Since 1987, I have assisted the Cook Islands Conservation/Environment Service and, more recently, the Takitumu Conservation Area Project and the Avifauna Conservation Programme of the South Pacific Regional Environment Programme (SPREP) to plan and implement a recovery programme for the kakerori, a critically endangered forest bird endemic to Rarotonga. In 1989, the kakerori was one of the 10 rarest birds in the world, and classified as 'critically endangered' (Collar et al. 1994) with a population of just 29 birds. I calculated