Organ Pipe National Monument Preserves Desert
On the edge of the Tohono O'odham Reservation stands Organ Pipe National Monument, one of the best places to glimpse the rich ecosystem of the Sonoran Desert, with its tenacious, understated extravagance and the long sweep to the horizon. The landscape was forged in a series of cataclysms starting 110 million years ago caused by the bumping and grinding of gigantic crustal plates that shaped the topography of the entire Southwest. The 3,000-foot-high (914 m) Puerto Blanco Mountains are made of 18-millionyear-oldrhyolite, which is really just molten granite spewed out and cooled at the surface instead of deep in the earth. That jagged, unsoftened volcanic history has created an uncompromising landscape, with starkly tormented ridgelines, jagged, gaping canyons, and long rocky slopes.
Deep in the monument burbles Quitobaquito Springs, where a 30-gallona-minute spring gushes 2,000-year-old rainwater that runs down a grassy wisp of a stream into a pond. Forced to the surface by a fault that has created an underground dam of crushed rock, the miraculous spring has nourished human beings for millennia. It nurtured desert-dwelling Indians for thousands of years and saved thousands of lives during the California gold rush, when it provided one of the few reliable water sources on the aptly named “Devil's Highway” between Tucson and Yuma.
The Tohono O'odham call the spring A'al Waipia (little wells) and farmed it until the government bought them out in 1938 and destroyed one of the oldest human settlements in North America. Now, the pond harbors endangered pupfish, remarkable Ice Age survivors that can tolerate hot, salty, low-oxygen water, but not the excessive pumping of groundwater and the voracious introduced fish that have degraded the streams, ponds, and seeps where it used to live.
The spring has played a vital role in the myths and survival of people stretching back at least 12,000 years, which is the age of finely shaped spear points left by long-vanished mammoth hunters. Although scientists have surveyed less than 3 percent of the monument, they have located more than 400 archaeological sites. When the first Europeans arrived, they found the peaceful and deeply spiritual Tohono O'odham living here, nurtured by a rich culture exquisitely adapted to surviving in a land where it can go a year between rains. They farmed the deep desert, relied on scattered springs and tanks, and regarded the world with reverence and wonder.
The monument also harbors the smoothed and sculpted Sonoyta Mountains, composed of pinkish granite, which cooled deep beneath the surface instead of frothing to the surface like the rhyolite Puerto Blancos. The sunny exposures and cold-air-shedding slopes nurture a surreal wealth of cacti, plus the bizarre elephant tree. A single elephant tree, which thrives in Sonora, Mexico, where the bulk of the Sonoran Desert dozes in the sun, perches on a hillside overlooking the road. Squat, thick, strange-leafed, and parchment-barked, the bulbous, otherworldly limbs of the elephant tree have skinlike folds of waxy bark.
The organ pipe and senita cacti that dominate the basin seem no less aesthetic and dramatic. The linear saguaros jostle with the orange-spined, pleated organ pipe and the smooth, gray-bearded senita. More frost-sensitive than the stately saguaro, organ pipe and senita occur together nowhere else in the United States, although they define the Sonoran Desert in Mexico. They have evolved all sorts of adaptations to heat and drought. For instance, their specialized metabolism allows them to absorb the sun's energy during the day, but hold their breaths until nightfall when they can open their pores and finish photosynthesis with minimal water loss. They have transformed the leaves they wore in the tropics where they originated into needles, which block up to 80 percent of the sun at their delicate growing tips, protect them from hungry nibblers, and even insulate them against the rare snows.