You can live weeks without food, so it is rarely the first emergency. How to find food in forest, mountain, desert, coast, tropics, and cold country — the easiest, lowest-risk calories first, which sources to skip, and how to cook it safely.

Almost every landscape hides water if you know how to read it. How to find water in forest, mountain, desert, coast, tropics, and snow country — the signs that point to it, the sources to trust, the myths to skip, and how to make what you find safe to drink.

When you have no tent, shelter is your first survival priority. How to pick a safe site and build a debris hut, lean-to, or tarp shelter that keeps you warm and dry in wind, rain, cold, and snow.

Build a fire when conditions fight you — no lighter, high wind, soaking wood, or deep snow. Every ignition method from a pocket kit to nothing but your hands, plus how to beat each condition and put the fire out cold.

Boiling, filtering, chemicals and UV: what each one actually kills, which to use on which water, and the cryptosporidium gap that catches out hikers who carry only tablets.