Southeast Arizona is extraordinarily endowed with surprisingly high levels of species diversity or biodiversity. Although the stereotype that most people harbor of Arizona before they ever set foot here is often one of expansive deserts, these are merely the the lowest of landforms above which loom a surprising array of habitats. Driving or, better yet, walking from the base of one of our loftier mountain ranges to its highest peak constitutes a virtual trip (in terms of habitats) from Mexico to Canada. From Desert to Spruce-Fir forest in a mere few hours! All things considered we may well be the most biologically diverse area in North America north of Mexico! For within Santa Cruz and a few surrounding counties we have bragging rights to an astonishing variety of taxa. All these ﬁgures are for North America north of Mexico:
• About 500 Bird species recorded – representing about 50% of all the birds recorded in North America – including the most Hummingbird and Sparrow species in this area
• More Mammals than any comparable area in N. America – over 100 species
• The most Reptile species, including the most Lizards, in North America • High levels of Ant and Bee biodiversity
• More than 2000 native Plant species
Why, then, do we possess such unexpected biological treasures? In a word – Geology. Landforms and their arrangement as well as elevation changes help in part account for our high levels of biodiversity. Here lofty mountains rise precipitously from normally very ﬂat valleys in a Basin and Range topography so typical of much of the western U.S. and which stretches from Oregon well into Mexico. Nothing too unique in that then. However, our tall isolated mountains lie strategically positioned at a sort of biological meeting grounds or crossroads given our exact latitudes and longitudes. They trend North-South, connecting the temperate and tropical realms, allowing many southern species to reach the northern terminus of their ranges, while many Northern species barely make it into Northern Mexico.
Looking at a map of the major local biomes or bioregions in the Southwest quickly conﬁrms that a number of such key areas converge right here with Circle Z right in the thick of things. The Rocky Mountains sweep in from the North, lending us their Spruce-Fir Forests and a number of species more characteristic of higher latitudes. The Great Plains and the relatively high and cool Chihuahuan Desert trickle across from the East, providing such species as Scaled Quail, Ornate Box Turtles, and Lark Buntings. To the West we are dominated by the lower and warmer, and hence more diverse, Sonoran Desert. Finally, and bearing an inordinate level of importance, the Neotropical and Madrean (think Mexicoʼs Sierra Madre Mountains) provinces allow otherwise subtropical and tropical species to inﬁltrate our area. Many people are rightly awed by the presence of Jaguars, Ocelots, White-nosed Coati, and other “Mexican Specialties” in our Sky Islands – species whose ranges are mainly south of the U.S. border. We even used to periodically host Thick-billed Parrots before they were persecuted into their present rarity in Mexico and Mexican Grizzly Bears until they were pushed to extinction.
Add a great range of elevations to this every-which-way directional mixing of species and you have the perfect palette upon which Nature has painted its masterpiece of temperate biodiversity. Traveling from lower elevations into higher ones, an idealized view of our vertically-stacked habitats goes something like this: Desert (either one), Grassland, Chaparral, Great Basin Conifer Woodland, Madrean Evergreen Woodland, Pine Forests, and topping out with Spruce-Fir Forests and Montane Meadows eerily reminiscent of Canada. The very fact that the heavily wooded habitats within this retinue are perched above the relatively open and timber-free ones creates our famous moniker: Arizonaʼs Sky Islands. Islands of isolated forested habitats loom above virtual seas of deserts and grasslands.
Circle Zʼs large slice of protected Sky islands habitats include their own high levels of biodiversity. The biological centerpiece of the ranch is Sonoita Creek, which artfully meanders through protected conservation easements. Along its banks youʼll ﬁnd a Riparian Forest, rich in towering tree species. In the surrounding uplands you will variously see Grasslands, Desert Scrub, and hints of Oak Woodland. Each of these beautiful and unique habitats contain their own distinct, yet overlapping, complement of ﬂora and fauna – all here for you to enjoy at Circle Z.
Come on one of my free Nature Walks on Wednesday after breakfast (no, you wonʼt miss your horse riding!) or schedule a private Naturalist Saunter with me to discover things at you own pace and length. Either way, keep a keen eye open and you never know what might show up. Maybe youʼll be the one to see a Mountain Lion, a Gila Monster, an Elegant Trogon, White-nosed Coati, Gila Woodpecker, Clarkʼs Spiny Lizard, Gray Hawk, Gila Topminnow ………