Arizona’s approximately 73 million acres encompass a wide range of topographic features and climatic conditions which contribute to the diversity of ecosystems found throughout the state. Elevations range from about 75 feet above sea level (near Yuma) up to 12,643 feet at its highest point (San Francisco Peaks near Flagstaff). Generally, elevation across the state increases from west to east and from south to north.
Much of Arizona receives most of its precipitation during two seasons, the annual summer monsoon (July through September) and during the winter months, typically December through February, when storms carry moisture from the Pacific Ocean (Mock 1996). Annual precipitation ranges from less than three inches per year in the southwestern portion of the state to more than 40 inches at higher elevations in the White Mountains in east-central Arizona (Arizona State Climate Office 2021). Winter rain or snow represent the majority of precipitation in northern portions of the state, while precipitation occurs mostly in the form of summer rains in the southern portion. The Sonoran Desert, extending across the southwestern portion of Arizona, typically receives nearly equal amounts of summer and winter rain.
Variability in climates, elevations, landforms, vegetative communities, watercourses, and soil types creates many different environments throughout Arizona. These environments range from the hot, dry deserts of southern Arizona, through grasslands and woodlands in mid-elevations, to the cold and wet montane and subalpine forest environments in the higher elevations. In addition, isolated mountains throughout southeastern Arizona, known as “sky islands,” create steep elevation gradients resulting in rapid environmental changes over very short distances that can effectively operate as an isolating mechanism for many plants and animals.
Throughout Arizona, aquatic systems and associated riparian areas play a major role in maintaining biodiversity. These aquatic systems cover only about 0.4% of Arizona’s landscapes, but play an outsized role in providing water and other resources for our state’s wildlife (Ffolliot et al 2004 and UA Cooperative Extension 2007). In addition to supporting Arizona’s 34 species of native fish and 27 species of sport fish, aquatic and riparian communities provide foraging, nesting, shelter, and water for a large percentage of terrestrial wildlife species in Arizona. Migratory birds, bats, and pollinating insects also depend on these vital travel corridors for daily and seasonal movements as well as annual migrations between North and South America.
Several important rivers flow through Arizona, the largest being the Colorado River which runs through the Grand Canyon and forms the western boundary of Arizona with California. The Gila, Salt, and Verde rivers drain the northern-central portion of Arizona, and carry water to reservoirs that support the cities in central and southern Arizona. The north-flowing San Pedro River in southern Arizona is one of the last remaining free-flowing rivers in the desert southwest. This river provides critical resources for a great diversity of migratory birds and other native wildlife (Stromberg and Tellman 2009). Many smaller creeks and tributaries have perennial or intermittent flow while springs, ciėnegas (marshes), and stock tanks (livestock ponds) are scattered throughout Arizona, providing valuable habitat and water for wildlife use. These terrestrial and aquatic ecosystems that exist across the Arizona landscape support diverse fauna and flora and form the foundation for the AWCS habitat-based approach to conservation.