What does it mean if one-third of irrigated acres in California go out of production? Well, depends on your perspective. First, it does not mean the end of agriculture in California, because two-thirds of irrigated agriculture would persist. That’s 6 million acres of irrigated agriculture, which is rather a lot.
Does it mean that your fruits and veggies will get more expensive? Does it mean that non-Californians will never have an almond again? Should you be hoarding wine? I don’t know. That depends on how the transition happens. The only thing that looks inevitable to me is that meat and dairy will become much more expensive. Relatively cheap feed, like alfalfa and silage, is the underpinning for cheap meat and dairy. I don’t see how those can remain cheap, nor how meat&dairy can withstand the way resource consumption intensifies with each step up the food chain.
Will the agricultural economy collapse? It doesn’t have to. Some two-thirds of it will remain, probably where the water resources were richest in the first place. The Sacramento Valley, the coastal valleys, Yolo, the northeast side of the San Joaquin Valley will be able to keep farming. Places that are poor now will become poorer until they are abandoned or find new industries.
Would retiring lands really suck for the people who are now farming them? It could. Again, it depends on how it happens. But many of the problems caused by farms going out of production are problems of poverty. Those can be addressed with things that may be more available than water, like re-training for other careers or monetary support or funding for re-location.
What about the empty barren land, with poisonous salt dirt-devils swirling everywhere? That’s the Salton Sea, you guys. In the San Joaquin Valley, it would return to scrub. Not every inch of land has to be farmed.