The rate of loss of freshwater species diversity is the fastest for any of the world’s major biomes. Taxonomic groups with the highest proportion of threatened species tend to be those that rely on freshwater habitats. For example, according to the Living Planet Index, the rate of loss of freshwater biodiversity (1970-2000) was almost double that of marine and terrestrial biomes.
The comparative rate of loss of area of inland water habitat is difficult to assess but data confirm that the loss mirrors that for species. Over half of the 14 biomes that the Millennium Ecosystem Assessment
assessed have experienced a 20–50% conversion to human use but the comparison did not include inland wetlands. Accurate quantitative data for historical and current global extent of inland waters are difficult to obtain. Where reasonable data do exist, more than 50% of specific types of inland wetlands were lost during the twentieth century, suggesting a loss at least equivalent to that of forest and approximately 2.5 times the rate of loss of coral reefs.
For more information, see the CBD Technical Series No. 11 "Status and trends of biodiversity of inland water ecosystems"