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To enhance their conservation value, several hundred islands worldwide have been cleared of invasive alien rats, Rattus spp. One of the largest projects yet undertaken was on 43 km2 Henderson Island in the Pitcairn group, South Pacific, in August 2011. Following massive immediate mortality, a single R. exulans was observed in March 2012 and, subsequently, rat numbers have recovered. The survivors show no sign of resistance to the toxicant used, brodifacoum. Using pre and post-operation rat tissue samples from Henderson, plus samples from around the Pacific, we exclude re-introduction as the source of continued rat presence. Microsatellite analysis of 18 loci enabled comparison of genetic diversity of Henderson rats before and after the bait drop. The fall in diversity measured by allele frequency change indicated that the bottleneck through which the breeding population passed was probably around 50 individuals, representing a census population of about 60-80 animals. This is the first failed project that has estimated how close it was to success.

Climate change is often referred to as the defining challenge of our time, and it is well known that Pacific Island States are particularly vulnerable to the adverse effects of climate change. Indeed, these adverse effects are already very tangible for most communities across the region. Coastal features are visibly changing, with rising sea-levels, higher king tides and storm surges, saltwater intrusion and changing weather patterns posing an increasing threat to the livelihoods of Pacific Island communities. The threats are amplified by extreme weather events becoming more intense and more damaging as a result of climate change, with Cyclone Pam recently causing loss of human life and catastrophic damage in Vanuatu, and to a lesser extent in the Solomon Islands, Tuvalu and Kiribati. 2 While communities and governments—assisted by regional, international and nongovernmental organizations—are proactively building resilience and adapting to climate change, there is a real risk of much more severe and damaging impacts materializing in the coming decades.3 The threats are so severe that most, if not all, Pacific Island States face the threat of losing some or all of their habitable territory as a result of climate change, with related risks of the loss of traditional livelihoods and large-scale involuntary displacement

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