Papahānaumokuākea as a Refuge for Rare and Globally Significant Species
Many species of plants and animals still exist in Papahānaumokuākea that once occurred in the main Hawaiian Islands (as evidenced by their presence in the fossil record), but could not survive after the arrival of humans and their commensal mammals. In all, there are 23 species found in Papahānaumokuākea Marine National Monument that are listed under the U.S. Endangered Species Act, and there are undoubtedly many more that might be eligible for listing, especially in the case of terrestrial arthropods (Evenhuis and Eldridge 2004). Additionally, Papahānaumokuākea is home to 22 IUCN Red-Listed species. Furthermore,Papahānaumokuākea contains countless endemics, often species that have ranges limited to a single island. Four endangered endemic land birds are found in the Monument, and nowhere else in the world. The critically endangered Laysan Duck was once more widespread around the Hawaiian Archipelago but now occurs in only two places: 1) a small, relict population on Laysan Island where it breeds and forages around Laysan’s unusual hypersaline lake; and 2) in a recently translocated population at Midway Atoll. Papahānaumokuākea is the most important habitat for insitu conservation of a number of endangered species. Hawaiian Monk Seals are found only in Hawai‘i, with the main breeding subpopulations located throughout the Northwestern Hawaiian Islands and a small but growing population in the main Hawaiian Islands. This population represents one of only two monk seal populations remaining anywhere, as the monk seals of the Caribbean are extinct and the populations of the Mediterranean monk seals are perilously low, at below 350 individuals. In 1988, the National Marine Fisheries Service designated critical habitat for the Hawaiian Monk Seal from shore to 20 fathoms around every island, atoll, and bank of Papahānaumokuākea, except Sand Island at Midway Atoll. This habitat includes “all beach areas, sand spits and islets, inner reef waters, and ocean waters.” Papahānaumokuākea also provides nearly the entire nesting habitat for the threatened Hawaiian Green Turtle. On the undisturbed beaches of these remote atolls, both male and female turtles come ashore to bask on the beach in broad daylight, a behavior no longer seen in most other parts of the world. The critically endangered Hawksbill and Leatherback turtles, and the endangered Olive Ridley and Loggerhead turtles, are also found in Papahānaumokuākea. In addition, the waters of Papahānaumokuākea are home to more than 20 cetacean species, six of them federally and/or internationally recognized as endangered. Recent research by Johnston et al. (2007) indicates that Papahānaumokuākea contains two-thirds of the humpback whale wintering habitat in the Hawaiian Archipelago. This study documented for the first time breeding and calving activity of humpback whales within Papahānaumokuākea. Altogether, besides the 23 identified endangered species (U.S. ESA) found in Papahānaumokuākea, there are also hundreds, if not thousands, of endemic species. Papahānaumokuākea is the last or only home for these creatures, and they require continued protection to assure their existence. The terrestrial area of Papahānaumokuākea is very small compared to its marine area, and only the larger and higher islands are of sufficient size to support significant and diverse plant biota. All islands are dry, with minimal fresh water resources. Remarkably, given these limitations, the terrestrial areas of Papahānaumokuākea also support significant endemism. All the islands and atolls of Papahānaumokuākea except Gardner Pinnacles, Maro Reef and Midway support endemic species that are specific to their respective islands. This includes at least 145 species of endemic arthropods, six species of endangered endemic plants (including an endemic palm), and four species of endemic birds, including remarkably isolated species such as the Nihoa Finch, Nihoa Millerbird, Laysan Finch, and the Laysan Duck, one of the world’s rarest ducks. Three of these species (Nihoa Finch, Nihoa Millerbird, and Laysan Duck) are deemed critically endangered by the IUCN, and the Laysan Finch is listed as vulnerable. In addition, millions of seabirds use the area for breeding and foraging, and as a transit corridor for migrations to the north and south. At least six species of terrestrial plants found only in the region are listed under the U.S Endangered Species Act, some so rare that because of the difficulty of surveying these remote islands, they have not been documented for many years. The IUCN lists Cenchrus agrimonioides var. laysanensis from Laysan as extinct, though biologists hold hope that it may still exist. Amaranthus brownii, endemic to Nihoa, is deemed critically endangered by the IUCN, while Pritchardia remota is considered endangered. Although it has yet to be documented thoroughly, the terrestrial invertebrate fauna shows significant patterns of clear precinctive speciation, with endemic species described from Nihoa, Mokumanamana, French Frigate Shoals, Laysan, Lisianski, Pearl and Hermes, and Kure.