> Soil restoration requires fallow acreage cycles that are unsupportable given the acreage of idle land required when compared against the total of available arable land at present.
Fallow doesn't mean idle. Notably, raising animals on land that isn't producing crops is actively conducive to soil restoration and speeds the process, requiring less fallow time. Animals are already being raised on arable land, so a lot of this could be done without any more arable land--it just requires that instead of crops and animals being farmed in separate monocultures, they be intermingled cyclically or otherwise.
Some schools of thought note that animals are a less-efficient way of producing calories, but I'll note that reducing nutrition needs to "calories" is a hopelessly insufficient measure. If we consider the protein needs of the population, which are likely higher than most people are consuming, animals are a much more efficient means of obtaining protein. Animal farming is also criticized for its greenhouse gas emissions, but different animals have very different greenhouse gas emissions (i.e. poultry emit far less than cattle) and healthy soil sequesters carbon. The reduction of fertilizer use would also significantly reduce carbon emissions.
> Permaculture is little more than a product of the instagram-homesteader industrial complex intended to sell books and land speaking engagements.
I won't deny that Instagram overhypes permaculture, but there's plenty of hard scientific research being done on it as well.
> It produces at absolute max a third of the calories per acre of industrialized monocrop agriculture.
I am not sure where you're getting that number, but even if it's right, "at absolute max" discounts the inevitability of continued innovation. I agree the numbers aren't currently equal, but as I said before, nobody is saying these changes happen overnight.
> Where to source 200% more arable acres to make that transition is conveniently left as an exercise by it's proponents
As noted above, a lot of arable land is used to raise animals, and intermingling those animals with crops means the land you're claiming is "idle" is not. Further, when soil becomes healthier both become more efficient.
Also notable is that for permaculture purposes, a lot more land can be considered arable than would be considered arable for monoculture crops. The traditional rows of crops are actually pretty terrible for certain very reliable crops, such as potatoes, which benefit from more water retention--which happens when rocks and roots of other plants block water flow. Blueberries benefit from acidic soil, such as soil with pine needles in it--from pine forest which can in turn be treated as timber land.
> as is how to handle the massive increase in labor required to harvest from permaculture lands.
I'm hearing you talk about job creation like it's a bad thing.