Restoring Wildlife Habitat on Rat Island: Environmental Assessment

Restoration of natural ecosystem function on Rat Island promises to re-establish native seabirds and other native species, thus returning this wilderness island to a healthy natural community. This restoration cannot occur until the island is cleared of the invasive non-native rats that now dominate the living community. Introduced non-native species are a leading cause of extinctions in island communities worldwide. Increasingly, land managers are removing introduced species to aid in the restoration of native ecosystems. Rats are responsible for 40-60% of all recorded bird and reptile extinctions worldwide. Given their widespread successful colonization on islands and the resulting impact to native species, introduced rats are identified as key species for eradication. Most of the Aleutian Islands lying within the Alaska Maritime National Wildlife Refuge (NWR) provide important breeding habitat for seabirds, including many for which the Aleutians provide a substantial portion of their worldwide range. Norway rats are established on at least 10 Aleutian islands or island groups, and the diversity and numbers of breeding seabirds occurring on those islands are now conspicuously low. Rat-caused modifications to other components of the island ecosystems (e.g., other birds, plants, and invertebrates) are also evident. The restoration of Aleutian ecosystems through introduced predator eradications has long been identified as a priority for Alaska Maritime NWR, and the initial efforts have been directed to removing introduced foxes. The focus now has turned to rats. This Environmental Assessment evaluates the environmental effects of eradicating introduced non-native rats from Rat Island, located in the central Aleutians within Alaska Maritime NWR. The consequences of the No Action alternative are addressed along with the Preferred Alternative (Proposed Action hereafter) which is to eradicate rats from Rat Island employing an aerial broadcast of rodenticide, and subsequently maintaining the island in rodent-free status. The intent of the Proposed Action is to facilitate the restoration of the natural island ecosystem by improving habitat quality for native species