A Place for Wildlife
A few steps into the woods that border the San Pedro River, and I felt like I'd been delivered. After a dusty two-hour drive across parched Arizona desert, my friend Erik and I had walked into a scene straight out of Wordsworth: A smallish, mellow river gurgled gently beside us, the green canopy overhead shielded us from the desert sun, and all around was the sound and motion of birdshundreds of them, from tiny hummers to highly vocal Gila woodpeckers. We spent the rest of the day inching through the San Pedro's cottonwood forests, willow thickets, and mesquite-studded grasslands, frequently stopped in our tracks to observe a density and diversity of wildlife unlike anything we'd ever experienced. Birds, mammals, reptiles, and insectsall seemed to find the San Pedro every bit the sanctuary that we did.
The San Pedro River originates in Sonora State in Mexico and flows north into the Gila River not far from Phoenix; it is among the most important wildlife habitat on earth. The river's significance is readily apparent in the raw numbersthe San Pedro supports more than 400 species of birds, 80 mammals, and 40 reptiles and amphibians. Like any arid-lands waterway, it pumps the lifeblood of the surrounding ecosystem, water that supports not only the moisture-loving plants and animals found along its banks but also much of the ecological diversity of nearby, much drier uplands.
The San Pedro's location gives a further boost to its importance. It is within the northernmost finger of the Sonoran Desert ecosystem, and is at the northern limit of summer breeding grounds for many species rarely seen outside of Mexicoif you want to see an elf owl, northern beardless tyrannulet, or elegant trogon in the United States, this is the spot. And the river is also a crucial north-south corridor for migratory birds, including as many as 4 million neotropical songbirds each year. These circumstances are what makes it a mecca for birdwatchers from all over the globe; Birding magazine has called the San Pedro the best birding area in the world.
These are the major issues affecting desert riparian areas:
Urban sprawl that swallows up riparian habitat.
Polluted run-off from streets, yards, development, and agricultural operations that degrades water quality.
Population growth and increased groundwater pumping that create "water deficits."
Dams that dry up river beds and degrade aquatic habitat.
Channelization that straitjackets riverways.
Large-scale industrial use of rivers for mining, logging, grazing, and irrigation.
Over the last century a darker reality has steadily deepened the significance of this modest 140-mile-long waterway. The Southwest's deserts are a harsh environment; its living things have had to evolve in highly specialized ways to reap what little sustenance the desert offers. The flip side is that the desert-riparian ecosystem, with all its specialized creatures, is quite brittle. And given modern man's habit of either ignoring the environment or, failing that, brazenly engineering it, it's no surprise that the settlement and development of the Southwest has been disastrous for its rivers. All over the region, riparian habitat has suffered from myriad degradations: Cottonwood forests have been logged out; native plants such as willows have been routed by salt cedars and other introduced species that are useless as wildlife habitat; grasslands have been left impoverished by uncontrolled cattle grazing; "flood control" programs that dam and channelize rivers have robbed their surroundings of the nutrients and other benefits of naturally occurring floods; and irrigation and uncontrolled development have sucked the life right out of rivers such as the Salt, near Phoenix. The result is that the still-undammed San Pedro has become, as the Center for Biological Diversity puts it, the "last living river of the Southwest."
Details mentioned in this article were accurate at the time of publication