Question

Explain why the amount of rainfall a region receives is a better determination of whether it is a desert than temperature.

Answer 1

Because “desert” describes an arid environment — a sustained deficit of available water — precipitation (how much water falls) is the most direct control on whether plants, soils and ecosystems are water‑limited. Temperature alone does not determine the amount of water available.

Key points:
- Desert conditions are about moisture shortage. If too little rain (or snow) falls to support continuous plant cover, the area behaves like a desert regardless of temperature.
- Many cold places are deserts because they receive almost no precipitation (Antarctica and parts of the Arctic are the driest continents/regions). Conversely, many very hot places are not deserts because they receive abundant rainfall (tropical rain forests and some monsoon regions).
- Temperature matters only indirectly: warmer air raises potential evaporation and can increase dryness for the same rainfall, whereas cold lowers evaporation and can reduce drought stress. That is why climate classifications combine precipitation and evapotranspiration. But the ultimate limiting factor for desert ecology is the amount and timing of precipitation.
- A simple practical rule: regions that receive very little precipitation (commonly cited thresholds are ~250 mm/year or less, though criteria vary) are classed as deserts regardless of whether they are hot or cold.

In short, deserts are defined by lack of water, not by heat — precipitation is therefore the better single metric for determining whether a region is a desert.