THE SAN PEDRO RIVER DRAINAGE

[Thanks to Daniel Baker, who designed this essay for The Nature Conservancy, and to TNC for allowing us to display it!]

The Nature Conservancy has designated the San Pedro River as a "Last Great Place" because it is an intact, high quality ecosystem that has a chance of survival.

  • It is the last major undammed river in the Arid Southwest of the United States.
  • It runs through two Major Geographic Provinces,

The Apache Highlands and

The Sonoran Desert,

  • and it transitions between four major geographic provinces:

The Chihuahuan Desert,

The Sonoran Desert,

The Rocky Mountains,

The Sierra Madres.

 

 

 

This intersection of major ecosystems creates

INCREDIBLE BIOLOGICAL DIVERSITY:

  • A Globally important bird area (400 species)
  • The highest concentration of mammal species in North America
  • Four globally imperiled natural communities

And it's also of HEMISPHERIC IMPORTANCE:

  • The main neotropical flyway in the west -- ten times that of any other Western corridor.
  • a crucial pollination corridor for the Western hemisphere.
  • The longest continual archaeological record in the continental U.S.

CONCLUSION: THE SAN PEDRO RIVER BASIN IS A "KEYSTONE" TRANSITION ZONE THAT SUSTAINS BIODIVERSITY IN OTHER ECOREGIONS.

 

 

THE LOWER SAN PEDRO

(#99 in the diagram at right)

  • Its baseflow conditions are independent from the Upper San Pedro River.

 

  • It has the highest quality riparian area in the Sonoran Desert Ecoregion.

 

  • It has a largely unfragmented landscape.

 

  • Its wildlife corridors connect its adjacent "sky islands" (the Catalinas, Rincons, Galiuros, and Winchesters)

HOT SPRINGS CANYON --

its lower reaches are shown on the map at right, running southwesterly to its confluence with the San Pedro River at lower left on the map.

Hot Springs Canyon is one of the San Pedro River's largest tributaries -- over 100 square miles of drainage.

It is the meeting place of two major ecoregions -- the Sonoran Desert and the Apache Highlands.

It serves as a major wildlife corridor, linking the Galiuro Mountains and the San Pedro River.