The biological diversity of inland waters relies on ecosystems and habitats containing high diversity and large numbers of endemic and threatened species, which are unique or associated with key ecological processes. In addition, inland water ecosystems perform valuable ecological functions, and inland water species, genomes and genes are of social, scientific and economic importance. In addition to the direct benefits (food, income and livelihoods) that are derived from the biological diversity of inland waters, human societies also enjoy many other economic, social and cultural benefits from inland water ecosystems, such as water supply, energy production, transport, recreation and tourism. The essential ecological functions performed by inland water ecosystems include, inter alia, maintenance of the hydrological balance, retention of sediments and nutrients, and provision of habitats for various animals, including migratory birds and mammals. Other ecosystem functions are the breakdown of anthropogenic pollutants and the sequestering of excess nutrients.
Human changes to the landscape are extensive and accelerating, and they have significant consequences for inland water ecosystems. The construction of dams, navigation channels, the drainage of wetlands, flood control and irrigation systems are the most obvious signs of human intervention in the aquatic environment. Land-use activities in the catchment area, including agriculture, deforestation, mining, grazing, and industrial and urban development, all contribute to the degradation of rivers and lakes and other water bodies through water withdrawals and/or additions of nutrients, pollutants and sediments. Other human interventions, such as the intentional or accidental introduction of alien species, can also cause severe damage to inland water ecosystems. Most importantly, their impact may be individually cumulative over time, and some effects may be synergistic.