The Vietnamese Mekong Delta is one of Earth’s most agriculturally productive regions and is of global importance for its exports of rice, shrimp, and fruit. The 18m inhabitants of this low-lying river delta are also some of the world’s most vulnerable to climate change. Over the last ten years around 1.7m people have migrated out of its vast expanse of fields, rivers and canals while only 700,000 have arrived.