If you only do one thing, collect rainwater.

Use all the skills you have in relation to others - and that way we can do anything.

A really failing society has a lot of rules (or laws).

Too often, the pastoralist blames the weeds and seeks a chemical rather than a management solution; too seldom do we find an approach combining the sensible utilisation of grasshoppers and grubs as a valuable dried-protein supplement for fish or food pellets, and a combination of soil conditioning, slashing, and de-stocking or re-seeding to restore species balance.

The value of land must, in the future, be assessed on its yield of potable water. Those property-owners with a constant source of pure water already have an economically-valuable "product" from their land, and need look no further for a source of income.

We have to let nature put what's left together, and see what it can come up with to save our ass.

There are a few societies that show signs of having been very rational about the physics of construction and the physics of real life. Some of the old middle-Eastern societies had downdraft systems over whole cities, and passive, rapid-evaporation ice-making systems. They were rational people using good physical principles to make themselves comfortable without additional sources of energy.