Extinct: This category is used for species for which we have evidence that they are no longer extant. As many Hawaiian plants are very restricted in their distribution, some species presently placed in this category undoubtedly will be rediscovered. Unlike the IUCN Plant Red Data Book, we do not include in this category species such as Hibiscadelphus giffardianus and Kokia cookei, which are extinct in the wild but survive in cultivation. A question mark (Extinct?) is added after this category when a taxon has not been collected for decades or the known occurrences are no longer extant, but cast some doubt due to the lack of recent or specific information. Taxa with extra-Hawaiian distribution, but with no known extant Hawaiian populations remaining are noted.

Endangered: These are taxa in danger of becoming extinct throughout all or a significant portion of their range unless the threats jeopardizing their survival are alleviated. Taxa with extra-Hawaiian distribution, which are in endangered throughout all or a significant portion of their range in the Hawaiian Islands are noted.

Vulnerable: This category includes taxa likely to become endangered in the near future unless the threats to their survival are removed or reduced. In the Hawaiian Islands, most species in this category are threatened by extensive habitat destruction or modification or by other environmental disturbances. Taxa with extra-Hawaiian distribution that have imminent threats to the populations in the Hawaiian Islands are noted.

Rare: Many Hawaiian plants have small, localized populations. Species not believed to be endangered or vulnerable at present, but that could be considered at risk, are included in this category. Taxa with extra-Hawaiian distribution that have small, localized populations in the Hawaiian Islands are noted.

Apparently Secure: We do not believe that many of the Hawaiian plants included in one or more of the databases warrant being given a rank. We indicate these plants with the NS designation.  These taxa are usually restricted in geographical range if given a TNC rank of G3, and a NS by us, or are too widespread, abundant, or seemingly secure to warrant listing.
 

This ongoing conservation assessment has been developed through the collective efforts and expertise of personnel from the Bishop Museum, The Nature Conservancy, the Smithsonian Institution, and the U. S. Fish and Wildlife Service. It is a synthesis of the authors’ perspectives and knowledge gained separately from the interaction between the Hawaiian botanical community and from information generated through fieldwork and respective programs. Programs at the Bishop Museum and the Smithsonian are primarily focused on biology, classification and evolution of organisms. The USFWS is responsible for assessing and listing at risk taxa under the U.S. Endangered Species Act of 1973, and the Hawai`i Natural Heritage Program (HINHP, affiliate of The Nature Conservancy) maintains information on the rare plants, animals, and natural communities of Hawai`i.

The goal of the conservation assessment of Hawaiian plants is two-fold; to provide an up to date listing of the conservation status and to serve as comparison between the three principal systems currently used for evaluating conservation status (U. S. Endangered Species Act definitions, Hawaii Natural Heritage Program’s Global Rank Definitions, and IUCN Red List Categories).

Listing of plants by the Service lags behind this biological assessment because of the lengthy legal procedures that must be followed in order to formally list a species as threatened or endangered including sufficient written data in support of the proposed listing.

Factors considered in making the determinations, include:

• The number of collections of each taxon in the BISH collection, and the date of the most recent collection. Taxa with few collections or that have not been collected in the last 40-50 years usually are listed as "rare" or "extinct." Assignment to one of these 2 categories was determined by our knowledge of the quality of its habitat. For example, if the plant is restricted geographically to a remote, relatively undisturbed area, we usually assume that its population is relatively stable. However, if the number of individuals of a species becomes small or there is a clear threat, such as destruction by pigs, goats, or other feral animals or they lose the ability to reproduce, the species is categorized as “endangered.”
• Personal knowledge of the species and the condition of its habitat. Botanists and knowledgeable naturalists were interviewed and their field observations have contributed substantially to our evaluations.
• The geographical location or habitat type. Some ecosystems are more sensitive or more susceptible to degradation than others. This includes the potential for development or change; for example, many plants of coastal areas are considered "vulnerable," as much of this habitat is being developed.
• Distribution.  Species found on several islands usually were not placed into one of the IUCN categories, because a single disaster, human-caused or natural, would not cause their extinction. Exceptions to this are, of course, situations where there is a clear threat to a species throughout its range, especially when it has become extirpated on one or more island.
• Nature of, and potential for, threats. There is greater potential for the destruction of a species by human disturbance than by natural causes. For example, today more native species are destroyed by human-caused fires than those set by volcanic eruptions. Feral animals such as pigs, goats, sheep, and cattle have degraded vast areas of natural habitat in Hawai`i and pose one of the major threats to the native ecosystem and its components.