Practice question · Multiple choice
Two regions have identical mean rainfall; one supports dense settlement and the other does not. What is the likely difference?
Hints
- Ask what happens in a year that delivers half the average.
- A population sized to the mean meets a bad year. Then what?
Show the answer
B. Reliability: the bad years set the ceiling
Why
Famine is set by the worst years rather than the typical one, so variance is the binding constraint and the mean can mislead completely. Storage, irrigation and trade are all technologies for converting a variable supply into a reliable one, which is why they appear exactly where variance is high.
Practise Climate and Biomes
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