Complex sentence: Changbaishan Nature Reserve, established in 1960, was involved in the UNESCO's "Man and Biosphere" program in 1980 and became part of the world's biosphere reserves.After being approved by the State Council in 1986, it became a State-level reserve.
Split into simpler sentences: Changbaishan Nature Reserve, established in 1960, was involved in the UNESCO's "Man and Biosphere" program in 1980 and becomes part of the world's biosphere reserves. Approved by the State Council in 1986, it becomes a State-level reserve.