Cacti are succulent plants, adapted to store water in their thick, fleshy parts. This allows them to survive in environments where water is scarce. They exhibit a wide range of shapes and sizes and are a diverse plant family with a broad global distribution.
Native Home: The Americas
Almost all of the nearly 2,000 known cactus species are indigenous to the Americas. Their native range extends from western Canada, through the United States and Mexico, and across Central and South America, reaching as far south as Patagonia. Mexico is a significant center of cactus diversity, with the highest number of endemic species. While deserts like the Sonoran Desert in North America and the Atacama Desert in Chile are iconic habitats, their natural distribution encompasses a much broader array of environments within these continents.
Beyond the Desert: Surprising Habitats
Cacti thrive in diverse environments beyond deserts. Many species are found in tropical rainforests, often growing as epiphytes, clinging to trees rather than rooting in the soil. These “jungle cacti” absorb moisture from the humid air.
Cacti also inhabit high mountain elevations, with some species found above the tree line in the Andes. Coastal regions and some temperate zones within the Americas support various cactus species. The genus Rhipsalis contains the only naturally occurring cactus species found outside the Americas, Rhipsalis baccifera, present in parts of Africa and Sri Lanka.
Adapting to Their Locations
Cacti possess specialized adaptations for survival in varied environments. Succulence is their most notable feature, with fleshy stems storing water. These stems expand during rainfall and slowly release water during dry periods.
Spines, modified leaves, protect from herbivores and reduce water loss by creating shade. Many cacti also utilize Crassulacean Acid Metabolism (CAM) photosynthesis, a water-efficient process. They open stomata at night to take in carbon dioxide, minimizing water loss during hotter daytime hours. These features allow cacti to thrive in climates from arid deserts to humid rainforests.
Global Spread: Cacti Beyond Their Origins
Human activities have led to the introduction and establishment of cacti in other parts of the world. Many species, especially prickly pear (Opuntia genus), have been intentionally or accidentally spread by people for ornamental use, food, or animal fodder. They are now found in regions like Australia, the Mediterranean, parts of Asia, and Africa. In some non-native regions, these introduced populations have become invasive, outcompeting local vegetation and altering ecosystems. These populations exist due to human intervention, clearly distinguishing them from native habitats.