Sad. The future should be sustainable lab-grown fish meat.
And before somebody jumps in to say Omega-3, not only can you easily get that from plants but fish also get it from algae. They don't produce it themselves.
How about Vitamin B12? This article:
https://en.wikipedia.org/wiki/Vitamin_B12
says: "There are no naturally-occurring notable vegetable dietary sources of the vitamin, so vegans and vegetarians are advised[5][6] to take a supplement or fortified foods."
There is also this part:
https://en.wikipedia.org/wiki/Vitamin_B12#Plants_and_algae
but who eats much algae, among vegetarians? Wonder if Spirulina is one of those algae. Need to check. Spirulina as a food supplement is commonly available in capsule form.
A lot of meat is also artificially enriched with B12 though and a lot of meat eaters are also deficient so a B12 supplement is probably a good idea for most people anyway.
A lil while googling about them seemed to say no-one's sure what good or bad effects they have, if any. And they're in a lot of things:
"According to one study...foods with the highest relative phytoestrogen content were nuts and oilseeds, followed by soy products, cereals and breads, legumes, meat products, ...vegetables, fruits, alcoholic, and nonalcoholic beverages."
And well, Japan has the world's greatest life expectancy doesn't it? And they have soy everything.
That saying prefer almond milk myself.
Indoor food production either as mentioned here or as in bio reactors and hydroponics systems use something like 100-700 times less land for the same food production.
Think how much land could be given back to nature if we use these more efficient methods and managed to stabilize our population growth.
Forests and fields could be populated by wild animals again.
So if International Paper owns a square mile currently used for fast-growing trees, the value of the land is the value of the next lumber harvest, discounted over the amount of time left until it's ready, plus the harvest after that, discounted by even more time, and so on, forever. Then you add the value from a developer that thinks, "this plot is really close to Townsburg, and I could build houses here that would get annexed". So you add the value of the land as residential housing, times the probability IP would sell to the builder.
It's the same for food. Most farmland is rather far away from anywhere people might want to build houses. The few houses that exist nearby are only there because the people that live there need to be closer to the open land than the cities. So if it stops being useful for growing food, it's value drops to the next-best use, which is probably not housing. One of those uses might be preserved wildlife habitat. It all depends on where it is, and what it's next to, and the perceived value of a particular use.