The pond biodiversity index 'IBEM', a new tool for the rapid assessment of biodiversity in ponds from Switzerland. Part 2. Method description and examples of application

摘要

Ponds are now widely recognized to contribute significantly to regional freshwater biodiversity. Therefore, tools to easily and rapidly assess biological quality specificalIy for these aquatic habitats have been increasingly requested by conservation planners and nature managers. In c10se association with practitioners, we developed such a method for Switzerland; the pond biodiversity index "IBEM". The IBEM-Index is based on the assessment of the taxonomic richness of 5 groups: aquatic vege­tation, Gastropoda, Coleoptera, adult Odonata and Amphibia. No abundance data are necessary and genus level identification is required for alI groups except Amphibia (species level). The sampling methodology is a stratified random strategy and alIows the use of richness estimators to transform the observed taxonomic richness (Sobs) into true taxonomic richness (Strue). As the IBEM assessment folIows the methodology presented in the Water Framework Directive, it is based on the caIculation of the ratio of true taxonomic richness (Strue) to reference-based predicted richness (Sref)' Each of the five taxonomic groups is assessed separately and the overalI biological quality of any given pond (i.e. the IBEM-Index) is the average of the five ratios. This score is later converted into one of five quality c1asses for each pond: bad (O to 0.2), poor (> 0.2 to 0.4), moderate (> 0.4 to 0.6), good (> 0.6 to 0.8), and high (> 0.8 to 1). In this paper, the implementation of the IBEM-Index is described in detail. The sampling methodologies are developed (for the biodiversity and the environmental variables) as welI as the assessment methodology. FinalIy, two examples are presen­ted in detail, for a "good" quality pond and for a "bad" quality pond. The method implementation also includes a website (http://campus.hesge.ch/ibem) which a1lows the online caIculation of the index, and provides support for both sampling and assessment methodologies to users. The IBEM-Index is a rapid assessment method which gives an overalI value of pond biodiversity in terms of taxa richness and can be used, for example, in regional screenings or site monitoring in Switzerland. Moreover, as biodiversity is generalIy recognized as a good indicator of global ecological quality, the IBEM-Index can also be used to investigate ecosystem quality.