Biosphere reserves are designated by UNESCO as sites that promote sustainable development through conservation and research. They contain three zones - a core zone where human activity is prohibited, a buffer zone allowing limited use, and a transition zone permitting human settlements. India has 18 biosphere reserves, such as Nilgiri Biosphere Reserve and Sundarbans Biosphere Reserve. Biosphere reserves aim to understand and manage the relationship between social and ecological systems through interdisciplinary study.