Cacti are native to the Americas and can be found from the southern tip of South America to western Canada in North America. They usually live in areas that are relatively dry. Many cacti thrive in areas that are extremely dry, such as the Atacama Desert — one of the driest places on Earth.
Like all living things, cacti need water to survive. Given the areas where they live, though, water is often scarce. To compensate, cacti have developed special abilities that allow them to conserve the water they do receive and make it last a long time.
For example, the prickly spines of cacti are actually highly-modified leaves. Spines protect cacti from animals that eat plants and also help to reduce water loss by restricting airflow near the cactus.
Most cacti have extensive but shallow root systems that allow them to soak up any rainfall that may come their way. Specialized stems allow cacti to store water for a long time since rainfall is often sporadic in the deserts that cacti call home.
For example, a fully-grown saguaro cactus can soak up and store up to 200 gallons of water during a good downpour! Many desert travelers have learned that, in an emergency, a cactus can be opened to find life-saving fluids.
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