That depends on your definition of sustainable. Most almonds are/were grown using sacramento river, which can provide a self replenishing source of water.
It is more of a water use issue than a sustainability issue.
Was also thinking about the massive issue they have with the large monoculture meaning they can't really support self-sustaining populations of bees.
Of course, it's not just almonds that have this issue, wine regions in my country (NZ) have the exact same problem which they're belatedly trying to fix.
