Sonoran Desert
The Sonoran Desert sits across the border between the southwestern United States and northwestern Mexico. It is the wettest of the four major North American deserts, with both winter and summer rains, and is famous for the giant saguaro cactus, the towering plant with arms that you see in every Western film. The Sonoran is also home to more plant and animal species than any other desert in North America.
- Areaapprox. 310,000 km²About the size of Italy
- CountriesUSA and MexicoArizona, California, Sonora, Baja California
- Rainfall75 to 400 mm/yearWettest of the US deserts
- Iconic plantSaguaro cactusUp to 12 m tall, lives 150+ years
- BiodiversityHighest in North America2,000+ plant species
- Famous riverThe ColoradoFlows through the desert's western edge
Sonoran compared to other US deserts
The Sonoran is the third biggest American desert. It is also the wettest, the most biodiverse, and the only one with proper subtropical desert conditions.
What is the Sonoran?
The Sonoran Desert covers southwestern Arizona, southeastern California, most of the Mexican state of Sonora, and most of Baja California. It is a subtropical desert, much warmer than the higher-elevation Mojave and Great Basin deserts to the north. The Sonoran has two rainy seasons (winter rain from Pacific storms and summer thunderstorms from the Gulf of Mexico), which makes it green for parts of the year and supports an unusually rich variety of life.
The saguaro cactus
The saguaro is the iconic plant of the Sonoran and grows nowhere else. Mature saguaros can be 12 metres tall, weigh 2 tonnes, and live for 200 years. They grow incredibly slowly: a saguaro might be 60 years old before it first sprouts an arm. After heavy rains, they can absorb hundreds of litres of water and expand visibly. The white waxy flowers that bloom on saguaro tops in spring are the official state flower of Arizona, and provide food for bats, bees and birds.
Many other cacti also live in the Sonoran: the prickly pear, the cholla, the barrel cactus and the strange organ pipe cactus. The desert is sometimes called the "cactus desert".
The monsoon
The Sonoran has a famous summer rain pattern called the North American Monsoon or "Arizona Monsoon". From July to September, moist air from the Gulf of Mexico spirals into the southwest, producing dramatic afternoon thunderstorms. The desert turns green and wildflowers bloom. Flash floods can sweep down the normally-dry canyons. The monsoon is essential for the desert's wildlife, providing the water that supports the year's growth.
Wildlife of the Sonoran
Despite the dry climate, the Sonoran supports approx. 100 species of mammals, 350 species of birds, 100 species of reptiles and over 2,000 species of plants. Famous Sonoran wildlife includes the desert tortoise, the Gila monster (one of the few venomous lizards on Earth), the roadrunner (a fast-running cuckoo), the mountain lion, the coyote, the collared peccary (or javelina, a pig-like animal), and around 100 returning jaguars who occasionally cross the Mexican border. The famous Sonoran toad hides underground for most of the year and emerges only for the monsoon rains.
Deeper dive: the North American Monsoon, the border wall and Tohono O'odham culture
The North American Monsoon is much weaker than its more famous cousin in South Asia, but it is the dominant rain-bringing weather pattern for the Sonoran Desert and the entire American Southwest. The monsoon is driven by intense summer heating of the southwestern interior, which creates a low-pressure region that pulls in moist air from the Gulf of Mexico and the eastern Pacific. As the moist air converges over hot desert ground, it rises rapidly, cools, and produces towering thunderstorms with dramatic lightning and brief but intense downpours. The desert can receive a quarter of its annual rainfall in a single afternoon storm. The monsoon also brings dust storms (called "haboobs" by Phoenix residents using an Arabic loanword), spectacular walls of dust hundreds of metres tall that sweep across the desert ahead of advancing thunderstorms.
The US-Mexico border runs straight across the middle of the Sonoran Desert. Construction of the border wall under successive US administrations has had significant ecological consequences. Large mammals like jaguars, ocelots and Mexican grey wolves rely on being able to cross back and forth between protected areas in Mexico and Arizona, and the wall has cut these populations apart. Construction has also destroyed sections of fragile desert habitat including the lands of the Tohono O'odham Nation, an indigenous people whose traditional lands span the border. The Tohono O'odham have been particularly affected because the wall cuts across sacred sites and prevents tribal members from visiting relatives, ceremonial sites and traditional resources that lie across the border.
The Tohono O'odham (formerly called the Papago) have lived in the Sonoran Desert for at least 2,000 years. Their traditional way of life adapted brilliantly to the desert: they harvested saguaro fruit in summer, hunted small game, gathered mesquite beans and other wild foods, and farmed in the brief rainy season. The Tohono O'odham preserved a deep knowledge of edible and medicinal desert plants, much of which has informed modern scientific understanding of the Sonoran ecosystem. Today the Tohono O'odham Nation is the second-largest Native American reservation in the US, covering nearly 11,000 square km of southern Arizona, and has a population of around 35,000.
The country with most of the Sonoran is divided between the United States and Mexico.