Application of the red list index for conservationassessment of Spanish vascular plants

The International Union for Conservation of Nature (IUCN) Red List Index (RLI) is used tomeasure trends in extinction risk of species over time. The development of 2 red lists for Spanish vascularflora during the past decade allowed us to apply the IUCN RLI to vascular plants in an area belonging to aglobal biodiversity hotspot. We used the Spanish Red Lists from 2000 and 2010 to assess changes in level ofthreat at a national scale and at the subnational scales of Canary Islands, Balearic Islands, and peninsular Spain. We assigned retrospective IUCN categories of threat to 98 species included in the Spanish Red List of2010 but absent in the Spanish Red List of 2000. In addition, we tested the effect of different random andtaxonomic and spatial Spanish samples on the overall RLI value. From 2000 to 2010, the IUCN categoriesof 768 species changed (10% of Spanish flora), mainly due to improved knowledge (63%), modifications inIUCN criteria (14%), and changes in threat status (12%). All measured national and subnational RLI valuesdecreased during this period, indicating a general decline in the conservation status of the Spanish vascularflora. The Canarian RLI value (0.84) was the lowest, although the fastest deterioration in conservation statusoccurred on peninsular Spain (from 0.93 in 2000 to 0.92 in 2010). The RLI values based on subsamples of theSpanish Red List were not representative of RLI values for the entire country, which would discourage the useof small areas or small taxonomic samples to assess general trends in the endangerment of national biotas.The role of the RLI in monitoring of changes in biodiversity at the global and regional scales needs furtherreassessment because additional areas and taxa are necessary to determine whether the index is sufficientlysensitive for use in assessing temporal changes in species’ risk of extinction