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Conservation Science

Conservation Strategy - Conservation by Design

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San Pedro River, Arizona

The San Pedro River’s cottonwood-shaded corridor supports about 350 bird species and provides critical stopover habitat for up to 4 million migrating birds each year. The San Pedro flows north from the Mexican state of Sonora into Arizona to join the Gila River, one of only two major rivers that flows north out of Mexico into the United States. It also is one of the last few large undammed large rivers in the Southwest.

The mild climate around the San Pedro has attracted tens of thousands of newcomers in recent decades along certain parts of the river, increasing human demands on precious water supplies. It is estimated that the upper portion of the basin in the U.S. alone had a 2.3 billion gallon ground-water deficit in the year 2000.

San Pedro River
San Pedro River
© Harold E. Malde

Ecological Importance: The San Pedro supports nearly two-thirds of the avian diversity in the U.S.; about 100 species of birds breed around the river and an additional 250 species use the corridor for migration and winter range. It also provides habitat for 80 species of mammals including the elusive jaguar.

Partners: In the San Pedro's headwaters, The Nature Conservancy is working closely with Mexican partners such as, Institudo del Medio Ambiente y el Desarrollo Sustentable del Estado de Sonora (IMADES) to address critical conservation issues within that portion of the river basin. The Upper San Pedro Partnership is a collaborative effort between 20 local, state and federal agencies and non-governmental organizations tasked with developing and updating adaptive management plans on an annual basis to address water conservation efforts for the Upper portion of the San Pedro Basin within the U.S.

Conservation Action: On-the-ground conservation projects within the Mexican portion of the basin include range improvement and erosion control projects with private landowners to enhance watershed condition, and streamflow monitoring along the river. Within the U.S. the Upper San Pedro Partnership is working to implement conservation strategies near urban areas there, such as the construction of wastewater effluent recharge facilities for some of the largest municipalities. The Conservancy has worked with Bureau of Land Management and Department of Defense to establish conservation easements which retire irrigated agriculture and reduce ground water pumping along the upper parts of the river within the U.S. It is estimated along the Lower San Pedro alone that year round stream flows will increase by 20 miles from this approach in the next few years.

In 2002, the Conservancy acquired the 2,150-acre Three Links Farm along the San Pedro River

Explore the San Pedro River on the Last Great Places web site.
Arizona

San Pedro River Facts

  • Size: 140 miles
  • Location: The San Pedro flows north from the Mexican state of Sonora to join the Gila River in Arizona.
  • Plant Species: Fremont cottonwood, Goodding willow, velvet mesquite, sacaton, and the Federally endangered Huachuca water umbel
  • Animal Species: More than 80 species of mammals, including jaguar, coatimundi, bats, beaver, mountain lion, and many rodents; more than 65 species of reptiles and amphibians, including Sonoran tiger salamander and Western Barking Frog; more than 100 species of breeding birds, including the imperiled yellow-billed cuckoo; and, seasonally, more than 250 species of migratory birds. Remaining native fish species include the Gila chub which is proposed for federal listing as endangered, and the longfin dace, desert sucker, roundtail chub, Sonora sucker, and speckled dace.

How to Visit
The Nature Conservancy has the following preserves within the San Pedro Watershed that are open to visitors.

  • Pristine Aravaipa Canyon Creek flows through the length of Aravaipa Canyon Preserve, which is noted for its desert stream, majestic cliffs and bighorn sheep. Visit the preserve web page for more information.
  • Muleshoe Ranch Preserve is a 50,000 acre ranch operated to benefit rare native fish and semi-desert grassland ecological conditions. The ranch has been used in recent years to demonstrate the value of prescribed burning programs to the recovery of the semi-desert grassland habitat and to provide a base to allow the export of these techniques to other ranches in the basin and throughout Southern Arizona.
  • Ramsey Creek in Ramsey Canyon Preserve is a key drainage in the Huachuca Mountains, which are a critical portion of the San Pedro watershed. Guided walks are held at the preserve during the spring and summer. Visit the preserve web page for more information.
  • The Nature Conservancy also operates three preserves that are open to visitors by invitation and guided field trips. These preserves are Buehman Canyon Preserve, Bingham Cienega Natural Preserve and San Pedro River Preserve. They are operated primarily to benefit rare habitats and the species they harbor, such as the federally listed endangered Southwestern willow flycatcher, the imperiled yellow-billed cuckoo and increasingly rare amphibians such as lowland leopard frog.

Photography Exhibition
See Lee Friedlander’s photographs of the San Pedro River from The Nature Conservancy exhibition "In Response to Place."