Loonook, I agree with RumbleTiger's comment, it's a nice breakdown. I'd Exp you if I could.
The only flaw is that, as I said, our world doesn't have the normal distribution of high level casters. Protracted wars took their toll, and the few that managed to come out intact were the ones that dodged the draft and went into hiding.
Beyond that: Plant Growth is available, though not in the abundance of your breakdown. And, as mentioned, it adds a third to the output of a field. But if the field production is down by 50% (which sounds like a reasonable amount), then the total yield is still only 2/3 of normal after Plant Growth. So cities still need to increase land under the plow.
Farming more land takes more people, so a manpower shortage may spring up on the farms. More people needed on the farms means fewer people in other trades, and the ability to support an army becomes problematical, not only in terms of supplies (an army travels on it's stomach, as the old saying goes), but also in terms of warm bodies. Societies just don't have the people to spare.
But with a smaller army, and with a larger perimeter of lands to protect... The numbers begin to look ugly.
One impact might be social upheaval. The overly wealthy control much of the commerce, including foodstuffs, so the shortages will fall most heavily on the poorer people of the cities. If I recall correctly, it was something like this that lit the fuse on the French Revolution. The nobility literally held parties to celebrate the famine, and the ladies decorated their hair with tiny cakes.
Somewhere between the parties and the guillotine, the cakes disappeared.
Using Stone to Flesh is a brilliant way to produce meat, though I have no idea what kind of meat it would be, or how edible it would be. Let's look at the spell...
SRD said:
Stone to Flesh
Transmutation
Level: Sor/Wiz 6
Components: V, S, M
Casting Time: 1 standard action
Range: Medium (100 ft. + 10 ft./level)
Target: One petrified creature or a cylinder of stone from 1 ft. to 3 ft. in diameter and up to 10 ft. long
Duration: Instantaneous
Saving Throw: Fortitude negates (object); see text
Spell Resistance: Yes
This spell restores a petrified creature to its normal state, restoring life and goods. The creature must make a DC 15 Fortitude
save to survive the process. Any petrified creature, regardless of size, can be restored.
The spell also can convert a mass of stone into a fleshy substance. Such flesh is inert and lacking a vital life force unless a life force or magical energy is available. (For example, this spell would turn a stone golem into a flesh golem, but an ordinary statue would become a corpse.) You can affect an object that fits within a cylinder from 1 foot to 3 feet in diameter and up to 10 feet long or a cylinder of up to those dimensions in a larger mass of stone.
Material Component: A pinch of earth and a drop of blood.
So you could produce up to 70 cubic feet of "fleshy substance" from stone. (70.685775, if you want to get technical). That's about 2.3 tonnes, maximum, presuming you could maximize the yield.
But form appears to be important to this magic, as noted in the comment about a statue becoming a corpse, which implies human flesh around a human skeleton and human internal organs.
If you wanted a specific meat you'd need to start with a statue of the right type of animal.
So you'd want
Stone Shape first, then
Stone to Flesh, to make sure it was edible. Sculpt a sheep, or a cow with legs folded beneath so it fits in the 3 foot by 10 foot volume limit, then transform. Less than the 2.3 tonnes of the theoretical maximum, but still a good chunk of food.
If you just took generic rock and transformed it, I'd probably rule that it's fleshy but gelatinous, like part of an ooze. Form is apparently important to the magic.
In any case, it would be a pricey bit of food as well. A 6th level spell, cast at 11th level (minimum for the spell) would normally cost 660 gp for the
Stone to Flesh alone.
(1). If we add
Stone Shape to the preparation, it costs 150 more.
(2) A cow normally costs 10 gp
So either the world's economy suddenly goes communist, where magic is cast for free, or the price of meat is about to go way up.
(Now you know why high level spell casters got drafted. The kingdoms couldn't afford to pay them by the spell.
)
(1) According to "Spellcasting and Services", the cost to have a 6th level spell cast is caster level x 60. 11 x 60 = 660.
(2) According to "Spellcasting and Services", the cost to have a 3rd level spell cast is caster level x 30, squared. 5 x 30 = 150. Since this spell is 5th level for Wizard/Sorcerer, but only 3rd level for Cleric and Druid, I went with the lower price.
