Sonoran Desert
The Sonoran Desert is a North American desert which covers large parts of the Southwestern United States in Arizona and California, and of Northwestern Mexico in Sonora, Baja California and Baja California Sur. A desert can fool the eye. A sun-blasted plain of death turns suddenly into a landscape of sound, water, and life.

If the Sonoran Desert's a wasteland, why is the vegetation so thick that it's nearly impossible to see over, much less walk through unpoked? If life here has been sun-blasted to a minimum, why are the sandy washes scribbled with footprints from javelinas, mule deer, ringtails, and so many rodents that as many as 200 rattlers a square mile can make their living with a sit-and-wait hunting technique?

This seems to be an ecosystem in need of a public relations makeover. Yes, the Sonoran Desert does get parched and hot as hell. But its emblem, that saguaro standing with upraised arms, is not some lonely perch for vultures in the barrens but part of a forest of storage tanks juicy with life.

Within hours of rain, many will be spreading new rootlets to harvest the drops. The plants' accordion-like structure lets them swell with extra liquid, as a Gila monster's extra-large bladder is designed to do while it packs away food reserves in its expandable tail. During May and June, the driest months, when winter's rains have been all but forgotten by most, the saguaro and its even bigger southern counterpart, the Cardon cactus, crown themselves with extravagant, white, nectar-filled blossoms.

These nourish birds, insects, and especially bats, and are pollinated in return. The flowers then develop into succulent fruits, supplying meals and moisture to a still broader array of creatures, from iguanas to kit foxes, until the summer thundershowers begin.

Retiring to one of the many small trees that also characterize this desert, such as yellow paloverde, blue paloverde, catclaw acacia, ironwood, or honey mesquite, to rest and digest, the animals leave droppings full of seeds exactly where a saguaro or card needs to grow during its tender years: in the shade of a nurse plant. If life here is just hanging on by a thread, how is it that a saguaro may produce millions of seeds a year and live to be 250 years old?

With few winter touches of frost and dual rainy seasons half a year apart, the Sonoran region supports such a rich variety of flora and fauna that it seems almost lush compared with other deserts. In some experts' view, it isn't really a desert so much as a drier version of the subtropical thorn scrub found farther south in Mexico. However you define the Sonoran ecosystem, it is a spectacular illustration of how communities of organisms facing extreme conditions find ways not merely to endure but to flourish.

A good place to rest, this fold of shade at the arroyo's steep edge, and a good place to ponder. Two days ago, a July cloud-burst dropped an inch of rain here in Arizona's Saguaro National Park. Water is still seeping down the arroyo and collecting in pools. Bright green algae already coat the bottoms.

Mourning doves, cactus wrens, and hundreds of bees sip from the edges. And somehow, among these mountainsides of stones too hot to touch, tadpoles have materialized within the pools. Native Americans who paused beneath the same rock wall long ago left paintings of humans, creatures, and spirits. If, as it seems, the figures are keeping watch, they have witnessed many times before the drama of survival that is about to play out.