Salt is essential to our existence. Bloody wars have been fought over it, civilizations have risen and fallen because of its availability, and our own civilization depends on it every bit as much as oil.
Salt is obtained from two sources: Using seawater from our current oceans and mining halite deposits from ancient oceans. According to the Salt Institute, world salt production was 208 million tons in 2004, a figure that increases every year. In the context of our industrial civilization, there is an unlimited amount of salt – even far from the oceans, underground salt is staggeringly plentiful.
But consider salt availability after Peak Oil. If you live near the ocean, you can obtain salt using any of the dozens of ancient techniques – until rising sea levels erase suitable areas for salt flats. In the past, those living away from the coasts had certain options: they could obtain salt from animals that had consumed salt from subsurface deposits; they could obtain the salt directly from those deposits; or they could trade with those who harvested it from the far-away oceans – options that are in serious jeopardy post-Peak Oil.
Just as with oil, as our demand for salt grew we extracted the easy deposits first before moving on to the deeper (and harder to obtain) sources. Without heavy machinery, there are few accessible significant salt deposits inland.
If you intend to get your salt through animal protein, consider this: most livestock require salt supplements in addition to their feed. That salt must come from somewhere. Plus, aside from just keeping our bodies functioning, salt serves many other critical functions: preserving food, tanning leather, dissolving ice, and conditioning water. Life without abundant salt is significantly less comfortable than what we enjoy today.
Trade with the coasts is likely to develop as the sustainable solution to meet the salt needs of those living elsewhere, but it will take time for this natural system to develop (and with global warming affecting sea levels, production will be irregular at best – some believe the Roman Empire fell because of a slight rise in sea levels). It may also be worthwhile to figure out some simple salt reclamation methods. In the meantime, make sure your community design includes provisions for significant salt storage if you plan to live away from readily obtainable sources.