It has heavily under utilized land, abundance of insolation and plenty of water that could be desalinated
If we grew crops in these areas, then both food and water would be a function of energy.
Sure you can dump additives in the ground and boost this years crop but that isn't going to create long term healthy soil which can support farming. Fertilizers are just another dependency on fossil fuels.
Water is certainly a part of terraforming a desert, but only a part of it.
Southern California is one such place where the desert meets the sea. It is not underutilized, but it is undergoing a massive drought.