What migration? "up to 630 M people live on land below projected annual flood levels for 2100, and up to 340 M for mid-century, versus roughly 250 M at present

What migration? "up to 630 M people live on land below projected annual flood levels for 2100, and up to 340 M for mid-century, versus roughly 250 M at present" 250 million people already live in those annually flooded regions, so that's only another 400 million by the year 2100. You think political systems can't cope? China has 300 million migrant workers, most of whom re-migrate every year!! They're coping already. We just need a lot of trains.