dont confuse
nilgiri is first but gyan bharathi is first biosphere

Biosphere reserves are nominated by national governments and remain under the sovereign jurisdiction of the states where they are located. Their status is internationally recognized. often include one or more National Parks or preserves, along with buffer zones that are open to some economic uses. Protection is granted not only to the flora and fauna of the protected region, but also to the human communities who inhabit these regions, and their ways of life. Animals are protected and saved here

GREAT RANN OF KUTCH or Gyan Bhart is the largest biosphere in India having 12454Kmsq and the second is Gulf of Mannar in tamilnadu havingg area of 10500sqkm