THE CONVENTION on Biological Diversity 1992 defined biological diversity or biodiversity as: ‘the variability among living organisms from all sources including, inter alia, terrestrial, marine and other aquatic ecosystems and the ecological complexes of which they are part; this includes diversity within species, between species and of ecosystems”. The Yarlung Tsangpo-Siang-Brahmaputra-Jamuna river system comprises unique and diverse ecosystems and habitats for a large variety of flora and fauna including many endangered species. The biodiversity of living habitats and species brings beauty and vibrancy to the river system making it one of the most fascinating river systems of the world. The aquatic and terrestrial habitats of the river system are dynamic in themselves and also change in character over short and long distances due to the changes in altitude and geographical and climatic conditions in each basin and subbasin of the river system. From the high altitude Tibetan plateau with its drought-resistant shrubs and grasses which is home to the yak, to the forests at lower altitudes with unique plant diversity, and the tall reed jungles, grasslands, and wetlands of the floodplains, home to three of Asia’s largest herbivores-the greater one-horned rhino, the wild water buffalo and the Asian elephant, and the largest carnivore, the Bengal tiger, this river system showcases diverse environments and ecosystems.