Finding food in different environments: forest, mountains, coast, desert, Arctic and tropics

Your body burns energy all the time: to breathe, to keep warm, to walk. If you eat nothing, it takes the energy from its reserves, mainly body fat. In healthy people this works for a long time, but you become weaker, get cold more quickly and think more slowly. Without water, on the other hand, the body is in danger of death within a few days, faster in heat.

Every search for food is therefore a calculation. What you find must provide more energy than searching, freezing and sweating cost you. Leaves provide very little, nuts, fish, fat, insects and mussels far more. Someone who stays in shelter and moves little needs much less.

Digestion needs water, especially with protein-rich food. So when water is short you eat little, and above all little protein. In the desert it is often better not to eat at all than to chew dried meat without water.

In the temperate forest the season is decisive. Summer and autumn bring berries, hazelnuts and beechnuts – beechnuts only roasted and in small amounts – plus insects and fish. In winter and spring there is hardly anything. In the mountains there is almost nothing above the tree line; there descending into the valley is wiser than searching.

The coast is often the richest environment, with mussels, snails, seaweed and fish. But the tide, waves, slippery rocks and invisible shellfish toxins lie in wait there. In the desert there is very little food, and movement costs water; there saving water comes above everything. In the Arctic plants are almost completely absent, fat becomes vital, and the liver of polar bears and seals is poisonous because of its extremely high vitamin A content.

The tropics look lush, but many plants are poisonous and water is often contaminated. There you only eat fruits that local people also eat, cook everything else thoroughly and boil water. Insects and fish are often the safest source of protein there.

The biggest danger when searching for food is not hunger but the risk you take for it: climbing over slippery rocks, crossing a stream, going too far onto tidal flats. An injury, a fall into cold water or hypothermia are much more dangerous in an emergency than a few days without food.

Plants and fungi are another danger. "Testing" unknown things is not a safe method; many deadly poisons cannot be detected that way. Stick to the few species you really know and leave mushrooms out altogether.

Fishing, trapping and hunting are illegal in Austria and Germany without a fishing licence or hunting rights. They can only be justified in genuine danger to life, and even then animal welfare applies: check traps often, kill animals quickly, dismantle all traps afterwards.

In short emergencies of one or two days, searching for food is usually not worth it. Then it is wiser to save energy, stay warm, drink and wait for help. Food you carry is rationed.

In longer emergencies, when no quick rescue comes, food becomes more important. Then you look specifically for energy-rich, safe sources near your camp and combine trips. Best of all, though, pack enough food for one extra day before every trip.

The US Army survival manual deals with food only after shelter and water and describes separate sources and dangers for each climate zone. The rule of thumb "weeks without food, days without water" is a rough guide; how long it really works depends on temperature, exertion and health.

Lean meat alone, without fat and without carbohydrates, is not enough in the long run – the body also needs fat and starch. That is why nuts, fish with skin, insect larvae and fat in cold regions are so valuable.