Diversity, function and impairment in freshwaters: new dimensions for conservation and ecosystem services

Alongside increasing evidence that the world's freshwater ecosystems contribute disproportionately to global biodiversity has come the realisation that they also provide irreplaceable goods and services with major utility to people. The need to exploit such services for human benefit, while simultaneously conserving the ecosystems that provide them, presents a major difficulty.  Moreover, the challenge is made particularly difficult because freshwaters are affected by multiple stressors that arise at a range of spatial and temporal scales both internally and across their floodplains, riparian zones and catchments.  In this overview, we draw on recent studies that reveal some of the ecological problems in conserving, exploiting and restoring the Earth's increasingly impaired freshwater ecosystems.  Key research needs include improved understanding of links between ecological structure, species interactions and emergent functions; methods to identify and predict the ecological effects of stressors acting in combination; and basic understanding of how best to reverse the effects of large-scale, long-term impairments.  Key management needs include the implementation of whole-ecosystem approaches to freshwater management; appropriate valuation of freshwater ecosystem services in the face of damaging actions; and the search for governance models that foster appropriate management actions.