This paper reviews the issue of freshwater biodiversity, from the time of its introduction on national and international bases. The project was initiated in co-operation by the International Union of Biological Sciences, the International Society of Limnology Working Group on Biodiversity in Freshwater Ecosystems and the Hydrobiological Committee of Hungarian Academy of Sciences. The first International Union of Biological Sciences International Workshop on Freshwater Biodiversity was convened at Balatonfüred, Hungary during 25-28 August 1996. A framework was developed and a wide scale project, BIODIVERSITAS, was worked out by Prof. Hiroya Kawanabe and Dr. Christian Lévesque. This project became one of the main issues of the International Union and has been incorporated into the activities of the United Nations Educational, Scientific and Cultural Organization. Several national and international meetings have been held dealing with particular fields in relation to species richness of aquatic ecosystems so that the topic has became a broad scientific, social, popular, political and economic issue. Scientific questions already cover nearly all aspects of biodiversity, for example, how to measure indices, and how to manage and preserve species richness in the most endangered aquatic habitats. Inventorying, monitoring and conservation of biodiversity in freshwater are of vital importance. All freshwater plant and animal species (invertebrates and vertebrates) are more or less threatened by human activities. Any decrease in diversity of aquatic species may indicate harmful human impacts, and whenever these activities increase, the living world of rivers, lakes and reservoirs is degraded. The rehabilitation of degraded aquatic systems has been a major limnological issue all over the world.
Freshwater biodiversity is studied in all types of habitats: lakes, reservoirs, rivers and wetlands and includes species from bacteria to aquatic vertebrates, and focuses on functional aspects and habitat differences (lake shores/ecotones, open waters and benthic habitats). Research on freshwater biodiversity can best be organized according to selected water bodies on different continents.
The ‘status quo’ of freshwater stocks is of crucial importance on local, regional and global scales. A crucial point is the high-level training of specialists and improving public-relations in order to make communities understand all aspects concerning ecological crises (e.g., habitat and biodiversity erosion and their consequences on nature and human beings). However, special interest must also be afforded to soil and sediment biodiversity, microbial biodiversity, human dimensions and genetic diversity in both land and aquatic systems.