The International Union for Conservation of Nature (IUCN) Red List of Threatened Species uses 5 quantitative criteria to allocate species to 9 categories of extinction risk. The criteria are based on ecological theory (1, 2), and are therefore subject to modification and critique. With pros and cons (3-6), and intrigues (7, 8), the list has established itself as an important tool for assessing the state of biodiversity globally and, more recently, regionally.
We all carry codes of some sort; that is, unique alphanumeric labels identifying our membership in a collectivity. Some of those codes (e.g., a videoclub customer number) make sense only locally, some do internationally (e.g., passport number). Species are also members of the club of biodiversity and, by virtue of our modern concern for their conservation, the status of many taxa has been allocated to alphanumeric categories under different rationales such as extinction risk or trading schemes (5, 9-13). Contradiction emerges when taxa might be threatened locally but not internationally, or vice versa.
In the journal Biological Conservation, a recent paper (14) has echoed the problem for the seagrass Zostera muelleri. This marine phanerogam occurs in Australia, New Zealand and Papua New Guinea, and is listed as “Least Concern” (LC) with “Stable” population trend by the IUCN. Matheson et al. (14) stated that such status neglects the “substantial loss” of seagrass habitats in New Zealand, and that the attribution of “prolific seed production” to the species reflects the IUCN assessment bias towards Australian populations. The IUCN Seagrass Red List Authority, Fred Short, responded (15) that IUCN species ratings indicate global status (i.e., not representative for individual countries) and that, based on available quantitative data and expert opinion, the declines of Z. muelleri are localised and offset by stable or expanding populations throughout its range. Read the rest of this entry »