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The desert is the driest biome.
Some deserts, such as the Sahara, get less than an inch of rainfall in an entire year. The flora and fauna that survive there have to be tough. Desert plants have evolved strategies to save water. In wet biomes, plants can have very large leaves—and they use them to catch as many rays as possible—but large leaves also lead to water loss. To conserve water, desert plants have very tiny leaves, or no leaves at all, transferring the work of photosynthesis to their trunks or stems. That’s why cacti have green “trunks.”