But "usable for agriculture" implies "has soil" to me. We're talking about moving the soil to a more temperate zone, and we're not talking about the current population of the planet, we're talking about the human species surviving.
(I'm trying to find a sea rise map that looks right by eye and not having much luck. Here's the North Atlantic at 10m[1]. Surely that's not enough flooding?)
[1] https://coastal.climatecentral.org/map/4/-10.3532/51.4503/?t...