desalinated water is used all over the world. But the cost to too high to make it useful for anything but drinking water. Its just too expensive for large scale commercial irrigation.
But there will come a time when desalinated seawater is cheap enough for large scale commercial irrigation.
When that happens — the world change very deeply. and very profoundly.
I think that will happen in the next decade.
Might come to pass in combination with vertical industrial factory agriculture and hydroponics.