The ecoregion represents the swath of semi-evergreen forests along the upper reaches of the Brahmaputra River, which flows through Assam and West Bengal. The region has been densely settled by people, its forests cleared, and the land extensively cultivated for thousands of years. From June to September, the southwest monsoon brings 1,500–3,000 mm of rainfall, causing the river to flood and enriching the floodplain. While the monsoon season is hot and humid, the winter is cold and dry. The ecoregion’s vegetation, adapted to these environmental and climatic variations, is broadly classified as semi-evergreen forest. It supports the world’s largest single population of greater one- horned rhinoceros and large populations of Asian elephants.