Protecting aquatic ecosystems

Terrestrial ecosystems are all water dependent, although water provides different functions - if not as habitat, then as a matrix, nutrient carrier and cooler. The river flow needed for healthy riverine ecosystems is often known and referred to as "environmental flow". The water needs of most other ecosystems is less well known. Seen from a global perspective, the terrestrial ecosystems in the temperate and tropical zones represent massive consumptive water use, representing almost 90 percent of the whole evapotranspiration (or "green water" flow) from the continents. Seen from a catchment perspective, protection of ecosystem water needs basically demands a sharing of the precipitation over the catchment between humans and ecosystems. At the smaller scale, management of ecosystem water needs tends to be "place-based" and linked to endemic species, biodiversity etc.

This strategy features in the framework of Agenda 21 as formulated at UNCED (Rio de Janeiro, 1992), now coordinated by the United Nations Commission on Sustainable Development and implemented through national and local authorities.