L?na?i is the sixth largest of the Hawaiian Islands and once formed part of the larger island of Maui Nui, which also included Maui, Moloka?i and Kaho?olawe. L?na?ihale, meaning ?house of L?na?i,? is the highest ridge that comprises the summit of the island at 1030 meters, and was formed by cavitation and collapse of the ancient volcanic summit, leaving what is now a high ridge. The L?na?ihale IBA consists of all parts of the island above 2,000 feet elevation and encompasses 2,195 hectares, including the summit ridge, adjacent side-ridges, and the portions of slopes below the summit that are covered in native ferns. L?na?i is in the rain shadow of higher and more massive mountains on Maui, and the upland areas of L?na?ihale receive between 760 and 1015 mm of rain each year. Northeasterly trade winds provide additional moisture from fog drip (moisture collected by vegetation from low clouds and fog) and this represents a significant contribution to the island?s aquifer. The vegetation over much of L?na?i was cleared for cultivation of pineapple over a century ago, and little natural habitat remains. Alien plants dominate most of the island, but the upper slopes of L?na?ihale support a remnant area of native forest, shrubland, and ferns. A variety of mammals have been introduced to the island and become feral, including goats, cattle, sheep, and axis deer. Goats were eradicated from L?na?ihale in 1982, but overgrazing and browsing by remaining ungulates continues to cause significant loss of vegetative cover and erosion.
The avifauna of L?na?i has been decimated by severe habitat degradation, predation by alien mammals, and disease. However, a relatively large and extremely important nesting colony of the endangered Hawaiian petrel or ?ua?u (Pterodroma sandwichensis) was discovered recently on L?na?ihale, the highest part of the island. Hawaiian petrels were known to occur on L?na?i previously, but the large size of the colony was not realized until surveys were conducted in March 2006. The number of Hawaiian Petrels using the area is not known exactly, but there may be several thousand birds present during the spring pre-breeding and courtship period. The colony area covers the summit ridge of L?na?ihale, the upper portions of adjacent side-ridges, and areas of uluhe fern (Dicranopteris linearis and Diploptyrigium pinnatum) habitat on the slopes below. The only native forest bird still present on L?na?i is the ?Apapane (Himatione sanguinea), which occurs in very small numbers near the summit of L?na?ihale. A few additional seabird species nest in other areas of L?na?i in small numbers, including Wedge-tailed Shearwater or ?ua?u kani (Puffinus pacificus), Bulwer?s Petrel or ?ou (Bulweria bulwerii), White-tailed Tropicbird or Koa?e Kea (Phaethon lepturus dorotheae), and possibly Band-rumped Storm-petrel or ?Ake?ake (Oceanodroma castro).
The greatest threats to Hawaiian Petrels on L?na?ihale are alien mammalian predators, predation by alien Barn Owls, invasive alien plants, erosion and loss of vegetation caused by alien ungulates, and potential development of wind-energy facilities. Predation on Hawaiian Petrels by feral cats (Felis cattus) has been documented, and cats are now trapped on L?na?ihale, with plans to double the current trapping effort in 2008. Predation by alien Barn owls (Tyto alba) has been documented by pellet analysis, and control of Barn Owls has begun, with plans to develop a nest box trap. Rats are ubiquitous in the colony area and also likely prey on nests. The alien tree strawberry guava (Psidium cattleianum) is spreading rapidly through the uluhe fern habitat in which petrels nest. This invasive weed creates impenetrable thickets, crowding out all other plants and destroying Hawaiian Petrel nesting habitat. Plans are in place to establish a 2.4 hectare test plot where strawberry guava will be removed and habitat will be restored to a native plant community, which will provide petrel nesting habitat and improve watershed function. Browsing by feral ungulates and erosion continues to be a threat. Castle & Cooke (C&C) is committed to building a watershed protection fence around the uplands of L?na?ihale. The first of three fence increments has been completed, enclosing about 728 hectares. Ungulate eradication within the fenced watershed has begun, with landscape-level treatment with rodenticide to follow. C&C is planning to develop wind energy facilities on the northern end of the island. Radar surveys are being carried out to identify passage rates of Hawaiian petrels and Newell?s shearwater over areas where wind towers may be erected. C&C will fund habitat restoration and additional predator control to serve as mitigation for any take of Hawaiian petrel or Newell?s shearwater.
L?na?i is owned primarily (~95%) by Castle and Cooke Resorts. L?na?ihale and the area of Hawaiian petrel habitat is 100% owned by Castle and Cooke Resorts.
Little natural habitat remains on L?na?i, but the summit of L?na?ihale supports a remnant area of native forest, shrubland, and ferns. `Ohi`a (Metrosideros polymorpha) is the dominant canopy tree in the area, but strawberry guava (Psidium cattleianum) is encroaching from below. Thick mats of uluhe fern (Dicranopteris linearis and Diploptyrigium pinnatum) cover the upper portions of many steeper slopes, and most of the Hawaiian Petrels nest under these ferns.
The private owner, Castle & Cooke, has set aside the entire summit area of L?na?ihale for conservation purposes.