(March 25, 2021) Kauai, Hawaii — The International Union for Conservation of Nature (IUCN) updated the IUCN Red List of Threatened Species today. The IUCN Red List of Threatened Species is the world’s most comprehensive online source of information on the conservation status of the world’s plant, animal, and fungus species. Included in the updated list are 127 plant species unique to Kauai that were assessed in 2020. The effort was led by scientists at the National Tropical Botanical Garden (NTBG) and completes the assessment of all 255 Kauai single-island endemic vascular plants.

IUCN Red List assessments provide an essential tool for scientists and conservation managers around the world. By completing the Red List assessments for all of Kauai’s endemic plants, NTBG has verified that 5 percent are already extinct, another 5 percent are possibly extinct or extinct in the wild, with the remaining 90 percent classified as Threatened according to the internationally recognized IUCN Red List criteria. The majority of these were placed in the two highest categories: Critically Endangered (46 percent) or Endangered (41 percent), with only 3 percent assessed as Vulnerable.

At the same time, only 45 percent of these taxa are officially listed as Threatened or Endangered under the U.S. Endangered Species Act, demonstrating the importance of bringing Hawaii’s conservation challenge to national and international attention through the Red List.

The Hawaiian Islands are known for having one of the world’s highest rates of endemism (species found only in one specific location). Over millennia, adaptive radiation has led to the evolution of a highly diverse flora of more than 1,360 native plant species. Among the eight main Hawaiian Islands, Kauai has the highest level of endemism and diversity, in part because it is the oldest island.

However, Hawaii’s flora is threatened by invasive species, changing land use, and more extreme weather. It is estimated that at least 134 of Hawaii’s native plant species have gone extinct since the 1840s. With all of Kauai’s known endemic vascular plant species assessed for the IUCN Red list, the goal of assessing the endemic species across the Hawaiian Islands will help better evaluate threat risks and aid in the formulation of conservation strategies.

Even as the assessment of Kauai’s endemic plants was underway, NTBG staff and its collaborators at the Department of Land and Natural Resources, Department of Fish and Wildlife, and the state of Hawaii’s Plant Extinction Prevention Program, made significant progress locating at least nine previously unknown populations of endangered native Hawaiian plants. Botanizing in rough terrain and remote locations, aided by helicopter transport and using drones and other new technology, NTBG discovered or re-discovered previously unknown plant populations in Kauai’s most challenging and inaccessible environments.

With today’s updated IUCN Red List, 134,425 species around the world have been assessed, 54,127 of them plants, each given a rank in one of nine categories from species of “least concern” to “extinct.” Twenty-eight (28%) percent of all now assessed species are recognized as Threatened.

The mission of the National Tropical Botanical Garden is to enrich life through discovery, scientific research, conservation, and education by perpetuating the survival of plants, ecosystems, and cultural knowledge of tropical regions.

Learn more about the work of the National Tropical Botanical Garden at www.ntbg.org.

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