Monitoring Freshwater Biodiversity at Large Scales: An Assessment of Potential Indicators

Conservation of freshwater biodiversity is a priority for both government agencies and national and international conservation organizations. A number of large-scale conservation plans specifically targeting freshwater biodiversity have been, or will soon be, implemented across the globe. Although numerous potential biodiversity indicators have been proposed for monitoring the status of freshwater ecosystems, few of these indicators have been evaluated. Choice of indicator is especially problematic in many parts of the developing world, where biodiversity data are sparse in general and budgets are limited. In contrast, many developed countries have created freshwater biological assessment programs, which are generally based on measuring aspects of macroinvertebrate assemblages. However, macroinvertebrate-based assessments have not been generally applied to biodiversity conservation, and the extent to which macroinvertebrate-based measures reflect trends or responses in other taxa is unclear. We reviewed the extensive biodiversity and bioassessment literature to identify a practical set of biodiversity indicators for monitoring the success of freshwater conservation plans. After defining the properties that such indicators should possess, we concluded that no single extant indicator can adequately assess the biodiversity status of freshwater fauna. We highlight areas for further research and suggest combinatorial approaches that may prove adequate in the interim.