Freshwater in the form of rivers, lakes, groundwater and wetlands offers us a remarkably diverse array of natural functions and ecosystem services. However, there is clear and growing scientific evidence that we are on the verge of a major freshwater biodiversity crisis: in the 30 years between 1970 and 2000, populations of more than 300 freshwater species have declined by ~55 percent while those of terrestrial and marine systems each declined by ~32 percent.