Richly biodiverse, the wet rainforests and bogs of upper Kīpahulu Valley are a key refuge for many species of native Hawaiian plants and animals disappearing elsewhere. No trails or roads are planned there in order to thwart devastating non-native species from penetrating the Valley. Entry is allowed only to resource managers and scientists conducting research and management essential to understanding and protecting this rare relictual ecosystem.
In 1967, a group of scientists sponsored by The Nature Conservancy (TNC) explored the remote valley, conducting surveys of the plants and animals (read their report here). They observed several species of rare native Hawaiian birds, including the Maui Parrotbill, the 'Akohekohe, and even the Nukupu'u, which was previously considered extinct. Ninety percent of the 228 species of plants that they recorded were native. Such rich native biodiversity made the Valley biologically outstanding, and inspired efforts to preserve it.