Disappeared in sea level rise during the Upheaval. Former population center of 20 million. One of the most significant single displacement events of the climate crisis.
The Mekong Delta had twenty million people when it started going under. It went under over eleven years — not a single catastrophic event but a sustained process of saline intrusion, seasonal flooding that stopped receding, infrastructure failure cascading in sequence.
By 2042 it was functionally uninhabitable. One of the most significant single displacement events of the climate crisis, folded into the statistics of the Great Drought years because the timeline overlapped. The people went everywhere. Most didn't go back.