Although the very mention of Arizona may cause some people to turn the air-conditioning on full blast, this state is much more than a searing landscape of cactus plants and creosote bushes. From the baking shores of the lower Colorado River to the snowcapped heights of the San Francisco Peaks, Arizona encompasses virtually every North American climatic zone. Cactus flowers bloom in spring, and mountain wildflowers have their turn in summer. In autumn, the aspens color the White Mountains golden, and in winter, snows blanket the higher elevations from the Grand Canyon's North Rim to the Mexican border.
But it's the Sonoran Desert, with its massive saguaro cacti, that most people associate with Arizona, and it is here in the desert that the state's two largest cities -- Phoenix and Tucson -- are to be found. Due in large part to the relatively plentiful rains in the region, the Sonoran Desert is among the world's most biologically diverse deserts. In Arizona, rain falls during both the winter and the late summer. This latter rainy season, when clamorous thunderstorms send flash floods surging down arroyos, is known as the monsoon season and is the most dramatic time of year in the desert. The sunsets are unforgettable, but so, too, are the heat and humidity.
Before the introduction of dams and deep wells, many Arizona rivers and streams flowed year-round and nurtured a surprising variety of plants and animals. Today, however, only a few rivers and creeks still flow unaltered through the desert. They include Sonoita and Aravaipa creeks and the San Pedro, Verde, and Hassayampa rivers. The green riparian areas along these watercourses are characterized by rare cottonwood-willow forests and serve as magnets for wildlife, harboring rare birds as well as fish species unique to Arizona.
The saguaro cactus, which can stand 40 feet tall and weigh several tons, is the Sonoran Desert's most conspicuous native inhabitant. Massive and many-armed, these are the cacti of comic strips and Hollywood Westerns, but this desert is also home to many other lesser-known species of cactus, including organ pipe cactus (closely related to the saguaro), barrel cactus, and various species of prickly pears and chollas. Despite their spiny defenses, cacti are a source of food and shelter for many species of desert animals. Bats sip the nectar from saguaro flowers and in the process act as pollinators. Javelinas (collared peccaries), which are similar to wild pigs, chow down on the prickly pear fruit -- spines and all. Gila woodpeckers nest in holes in saguaro trunks, while cactus wrens build their nests in the branches of cholla cacti.
Just as cacti have adapted to the desert, so, too, have the animals that live here. Many desert animals spend the sweltering daytime in burrows and venture out only in the cool of the night. Under cover of darkness, coyotes howl, rattlesnakes and great horned owls hunt kangaroo rats, and javelinas root about for anything edible. Gila monsters, one of the few poisonous lizards in the world, drag their ungainly bodies through the dust, while tarantulas tiptoe silently in search of unwary insects.
Outside the desert regions, there is great diversity as well. In the southern part of the state, small mountain ranges rise abruptly from the desert floor, creating refuges for plants and animals that require cooler climates. It is these so-called sky islands that harbor the greatest varieties of bird species in the continental United States. Birds from both warm and cold climates find homes in such oases as Ramsey, Madera, and Cave Creek canyons.
Although rugged mountain ranges crisscross the state, only a few rise to such heights that they support actual forests. Among these are the Santa Catalinas outside Tucson, the White Mountains along the state's eastern border, and the San Francisco Peaks north of Flagstaff. However, it's atop the Mogollon Rim and the Kaibab Plateau that the ponderosa pine forests cover the greatest areas. The Mogollon Rim is a 2,000-foot-high escarpment that stretches from central Arizona all the way into New Mexico. The ponderosa pine forest here is the largest in the world and is dotted with lakes well known for their fishing. The Mogollon Rim area is also home to large herds of elk. At more than 8,000 feet in elevation, the Kaibab Plateau is even higher than the Mogollon Rim, yet it is through the Kaibab Plateau that the Grand Canyon cuts its mighty chasm.
