Fresh waters offer intricate diversity, from small hot springs to huge floodplain systems, from temporary pools to big lakes, each containing significant proportions of the world's stock of inland water. In this collection is a great diversity of organisms, and of interesting relationships amongst them and with traditional peoples. There is thus every reason to value the diversity of freshwater systems and reasons for conserving them, from the ethical to the economic, can be listed no less than for terrestrial systems.

The approaches currently used to conserve the diversity of terrestrial systems, however, may be counter-productive for the conservation of freshwater systems. These approaches include emphasis on individual, often charismatic species, or on areas of high quality that can be boundaried and protected (fortress conservation) and rest on arguments that all species must be maintained for the system to function. The current decline in world biodiversity under our increasing impact suggests that these are failing approaches even for terrestrial systems. They may be disastrous for freshwater ones.