Fossil evidence for a diverse biota from Kaua'i and its transformation since human arrival

Coring and excavations in a large sinkhole and cave system formed in an eol ianite deposit on the south coast of Kaua'i in the Hawaiian Islands reveal a fossil site with remarkable preservation and diversity of plant and anima l remains. Radiocarbon dating and investigations of the sediments and their fossil contents, including diatoms, invertebrate shells, vertebrate bones, pollen, and plant macrofossils, provide a more complete picture of prehuma n ecological conditions in the Hawaiian lowlands than has been previously a vailable. The evidence confirms that a highly diverse prehuman landscape ha s been completely transformed, with the decline or extirpation of most nati ve species and their replacement with introduced species. The stratigraphy documents many late Holocene extinctions, including previo usly undescribed species, and suggests that the pattern of extirpation for snails occurred in three temporal stages, corresponding to initial settleme nt, late prehistoric, and historic impacts. The site also records land-use changes of recent centuries, including evidence for deforestation, overgraz ing, and soil erosion during the historic period, and biological invasion d uring both the Polynesian and historic periods. Human artifacts and midden materials demonstrate a high-density human presence near the site for the l ast four centuries. Earlier evidence for humans includes a bone of the preh istorically introduced Pacific rat (Rattus exulans) dating to 822 yr BP (ca lendar year [cal yr] AD 1039-1241). Vegetation at the site before human arrival consisted of a herbaceous compo nent with strand plants and graminoids, and a woody component that included trees and shrubs now mostly restricted to a few higher, wetter, and less d isturbed parts of the island. Efforts to restore lowland areas in the Hawai ian Islands must take into account the evidence from this study that the pr ehuman lowlands of dry leeward Kaua'i included plants and animals previousl y known only in wetter and cooler habitats. Many species may be restricted to high elevations today primarily because these remote locations have, by virtue of their difficult topography and climate, resisted most human-induc ed changes more effectively than the coastal lowlands.