Rarity, conservation status and their ecological basis. Scientific background and utility of application of red list criteria at regional levels

Abstract

This work reviews the relationships among the ecological basis of rarity, threat categories of species and the definition of their conservation status. When applying quantitative criteria to establish threat categories, there are many logical problems dealing with biodiversity conservation, biological problems dealing with the natural history of the species, and methodological problems linked to scientific design and reliability of the data; these limitations are assessed. It is not advisable to determine national or regional categories of threat when depending on speculative data without scientific credibility. This should be particularly worrying if regional rarity is based on purely biogeographical aspects (e.g., populations at the edges of total distribution ranges). Several alternatives are proposed to apply criteria determining the regional threat status.