In previous posts we’ve mentioned that we’re restricting ourselves to food grown within 100 miles of Tucson. But what’s contained within that 100-mile radius?

Our foodshed

Our local foodshed (image courtesy of 100-Mile Diet and Google).

Our “foodshed” includes most of southeastern Arizona as well as part of northern Sonora, Mexico. It goes from close to the New Mexico border in the east, to the border of Organ Pipe Cactus National Monument to the west, and from Phoenix to the north down almost to Magdalena de Kino to the south in Sonora. Besides Tucson, this area includes roughly half of the Phoenix metropolitan area, numerous smaller towns and cities, and the large Tohono O’odham Reservation.

Several large protected areas are found within 100 miles of Tucson, including Saguaro National Park, Sonoran Desert National Monument, Ironwood Forest National Monument, and Buenos Aires National Wildlife Refuge, as well as numerous smaller reserves and parks. Much of the land is included in the Coronado National Forest.

Tucson is at about 2,500 ft. in elevation and sits within the far eastern edge of the Sonoran Desert region known as the “Arizona Upland”. According to the Arizona-Sonora Desert Museum’s nice discussion of the Sonoran Desert’s regions, the Arizona Upland is the highest and coldest region of the Sonoran Desert. The flora in this region is dominated by saguaro (Carnegiea gigantea), palo verde (Parkinsonia spp.), and velvet mesquite (Prosopis velutina). It is a spectacular and diverse ecosystem(s). Roughly half of our foodshed is composed of Arizona Upland (judging by the Desert Museum’s map of the region).

Saguaro National Park

Sunset in Saguaro National Park

East of Tucson our foodshed includes a thin sliver of Chihuahuan desert along the San Pedro River (and elsewhere), a good deal of grassland, and numerous “sky island” communities (small mountain ranges topped with oak or pine forests). Apparently our 100-mile radius also includes a tiny bit of chapparal east of Phoenix. There are a few perennially-flowing rivers in the area: the San Pedro River, the Gila River, and the Salt River. Other rivers, such as the Santa Cruz River a mile from our house, are now dry except after heavy rains. There are a handful of man-made lakes in our radius, as well.

Southern Arizona has an amazing diversity of species, due to several factors. First, it is at a crossroads where temperate species from the north intermix with tropical species from the south (due to our subtropical climate). For example, we have mule deer, black bears and other temperate species intermingling with coatis, peccaries (javelinas) and other more tropical fauna (including jaguars and ocelots, until recently). This pattern is visible throughout the region’s fauna and flora.

Secondly, there is a broad east-west elevation and climatic gradient from the Sonoran Desert into the Chihuahuan Desert. Third, there are localized elevation gradients from the low deserts up to the tops of the sky islands (some of which are quite high; Mt. Lemmon near Tucson is nearly 9,000 ft. in elevation, while Mt. Graham to the east is over 10,000 ft. high). Finally, minor local variations in topography, climate and soils leads to additional faunal and floral variation over small spatial scales. All of this translates into impressive habitat and species diversity in Southern Arizona.

The climate in Tucson could be generally described as hot and dry. We get an average of 12 inches of rain a year (which is actually a lot by desert standards) and high temperatures are near or above 100° F for four months of the year. However, the climate is really characterized by five distinct seasons. We are currently approaching the end of the summer monsoon season, which is characterized by hot and humid tropical conditions and frequent thunderstorms. These thunderstorms are often spectacular, and have led Tucson to be considered the “Lightning Capitol of the World” by many meteorologists (although Florida also seems to claim that title). The monsoon usually lasts from early July to mid-September. High temperatures in Tucson during the monsoon are typically in the 95°-105° F range, with low temperatures in the 70°-85° F range. We get nearly half of our yearly rainfall during this 10-week period.

Lightning Over the Santa Rita Mts.

Lightning over the Santa Rita Mts.

The monsoon gives way to autumn, which is warm and relatively dry. Winter is generally mild (high temperatures are usually in the 50°-75° F range), though freezes are not uncommon and snow falls in Tucson every several years on average (we got an inch of snow at our house this past January). Spring is warm and dry, like autumn, and lasts from February through April. The fifth and final season is very hot and very dry, and is what is termed the “foresummer drought”. High temperatures during this period (May and June) can reach 115° in Tucson, with humidity in the single digits. Rainfall is rare, though we’ve actually gotten one decent storm during this period for each of the past two years.

All of the climatic and habitat variation I discussed above provides for a great diversity and abundance of wild foods in this region, which we plan to take advantage of during our local diet. In the deserts, the most important sources of wild plant foods include mesquite (Prosopis spp.) pods, palo verde (Parkinsonia spp.) seeds, desert ironwood (Olneya tesota) seeds, saguaro cactus (Carnegiea gigantea) fruit, prickly pear cactus (Opuntia spp.) pads and fruit, and cholla cactus (Cylindropuntia spp.) flower buds. There are many other minor sources of wild desert plant foods, such as agave, yucca, hackberries, and wolfberries, but those listed above are the ones present in greatest abundance. The mountains contain their own set of useful wild plant foods, including acorns from Emory oaks (Quercus emoryi), pine nuts (Pinus spp.) and juniper berries (Juniperus spp.).

Wild game is abundant, and though we do not anticipate drawing on this resource during our local diet, it ultimately should not be ignored in any truly sustainable regional food economy. The area has abundant deer (both mule deer and white-tailed deer), javelinas, cottontail rabbits, jackrabbits, several species each of quails and doves, and many other species which could be eaten if desperate. Tragically, some formerly important game animals, such as bison, pronghorn and turkeys, are now either completely gone or endangered in the region.

Insects are also abundant, and are a widely ignored and vilified source of nutrition. Our area has a long tradition of entomophagy (insect eating). The Tohono O’odham people of southern Arizona traditionally ate great quantities of white-lined sphinx moth caterpillars (Hyles lineata; Marci did her Master’s thesis on the cultural and nutritional value of this caterpillar). Other local edible insects include cicadas, grasshoppers, beetle (buprestid and cerambycid) larvae, and honeypot ants. This is another fantastic source of local food which should not be ignored (we all eat insects all the time anyway without knowing it!). We plan to eat a fair bit of insects during our local diet.

Next time I will discuss our sources of cultivated food, other than our own yard (which will get its own post later).