Extinction risk of the endemic vascular flora of Kauai, Hawaii, based on IUCN assessments

Abstract

The International Union for Conservation of Nature's Red List of Threatened Species (IUCN Red List) is the world's most comprehensive information source on the global conservation status of species. Governmental agencies and conservation organizations increasingly rely on IUCN Red List assessments to develop conservation policies and priorities. Funding agencies use the assessments as evaluation criteria, and researchers use meta‐analysis of red‐list data to address fundamental and applied conservation science questions. However, the circa 143,000 IUCN assessments represent a fraction of the world's biodiversity and are biased in regional and organismal coverage. These biases may affect conservation priorities, funding, and uses of these data to understand global patterns. Isolated oceanic islands are characterized by high endemicity, but the unique biodiversity of many islands is experiencing high extinction rates. The archipelago of Hawaii has one of the highest levels of endemism of any floristic region; 90% of its 1367 native vascular plant taxa are classified as endemic. We used the IUCN's assessment of the complete single‐island endemic (SIE) vascular plant flora of Kauai, Hawaii, to assess the proportion and drivers of decline of threatened plants in an oceanic island setting. We compared the IUCN assessments with federal, state, and other local assessments of Kauai species or taxa of conservation concern. Finally, we conducted a preliminary assessment for all 1044 native vascular plants of Hawaii based on IUCN criterion B by estimating area of occupancy, extent of occurrence, and number of locations to determine whether the pattern found for the SIE vascular flora of Kauai is comparable to the native vascular flora of the Hawaiian Islands. We compared our results with patterns observed for assessments of other floras. According to IUCN, 256 SIE vascular plant taxa are threatened with extinction and 5% are already extinct. This is the highest extinction risk reported for any flora to date. The preliminary assessment of the native vascular flora of Hawaii showed that 72% (753 taxa) is threatened. The flora of Hawaii may be one of the world's most threatened; thus, increased and novel conservation measures in the state and on other remote oceanic islands are urgently needed.

Collecting critically endangered cliff plants using a drone-based sampling manipulator

“…On Kauaʻi, one of the oldest of the Hawaiian high islands, where the field portion of this project was conducted, there are 250 single-island endemic plant species 2 . Most of these species are seeing significant population declines and habitat degradation, leading to 97% 3 being listed as endangered, critically endangered or extinct on the 2021 International Union for Conservation of Nature (IUCN) Red List of Threatened Species 4 . Nearly 90 of these Kauaʻi endemics are extremely rare and have been reduced to total populations of less than 50 individuals, which puts them under the management of the Plant Extinction Prevention Program.…”

Conservation Priority Index of species, communities, and habitats for biodiversity conservation and their management planning: A case study in Gulmarg Wildlife Sanctuary, Kashmir Himalaya

“…According to IPBES (2019), up to one million species of plants and animals are threatened by the risk of extinction. The most recent update of the IUCN Red List includes 142, 577 species [International Union for Conservation of Nature (IUCN), 2022] representing ∼7% of the biodiversity of the planet (Ronsted et al, 2022). The irony is that most plant species lack global risk assessment, and the lack of knowledge of which plant species are at risk of extinction limits our ability to frame conservation and management policies (Nic Lughadha et al, 2020).…”

Restoration of threatened plant species in Limahuli Valley on the Hawaiian Island of Kaua'i in the framework of the Global Tree Assessment

“…Hawaiian trees occur across a high diversity of habitats over a small geographical area, with isolation limiting colonization and leading to a high proportion of endemism with nearly 90% of the circa 1367 native vascular plant taxa being endemic to the islands (Sakai et al, 2002; Wagner et al, 2005). Isolated oceanic islands are characterized by high endemicity, but the unique biodiversity of many islands, including those in the archipelago of Hawai'i, is experiencing high extinction rates (Humphreys et al, 2019), primarily due to habitat disturbance and loss, competition with invasive species, spread of new diseases, and climate change, calling for urgent conservation measures of remote oceanic island floras in particular (Rønsted et al, 2022).…”

“…Of the eight major Hawaiian islands, the oldest island of Kaua'i harbors 673 or nearly 50% of Hawai'i's native plant taxa with 251 or 37% of these being single island endemics (Rønsted et al, 2022).…”