Sonoran Desert and Grasslands

Stretching across deserts, grasslands and mountains, the northwest Mexican state of Sonora is a land of expansive vistas and surprising beauty. Sonora's arid lands and sustaining waterways form one of the largest, most diverse and intact landscapes in North America.

The San Pedro River forms a meandering green ribbon in the surrounding desert landscape.
© Adriel Heisey

Location
A large portion of the state of Sonora lies within the embrace of the Sonoran Desert – a 55 million-acre desert expanse that also covers parts of Northern Baja California, southern Arizona and southeastern California. In the northeastern corner of the state, the rugged mountains of the Sierra Madre Occidental are bisected by meandering rivers and vibrant green riparian corridors. Surrounding these mountains are patchwork carpets of grassland prairies that provide habitat for a myriad of unique wildlife. Moving west, spectacular cactus gardens and thorn trees give way to the dune fields and cinder-covered plains of dormant volcanic regions. Along Sonora’s coastal boundaries, the life-giving waters of the Gulf of California, the lower Colorado River and the river’s delta are distinct and ecologically important counterpoints to the desert that surrounds them.

Animals

Sonoran pronghorn antelope
Bighorn sheep
American black bear
Long-nosed bat
Jaguar
Mountain lion
Black-tailed prairie dog
Mexican gray wolf
Mexican spotted owl
Peregrine falcon
Golden and bald eagles
Native fish and amphibian species

Why the Conservancy works here
The unique "Sky Island" ecosystems formed by the Sierra Madre Occidental mountain range are the headwaters for the major rivers of northwest Mexico, including the bi-national San Pedro River. By capturing precious rainfall, feeding tributaries and replenishing underground aquifers, these forested sky islands are critical for the long-term survival of both residents and wildlife on both sides of the border.

The San Pedro River emerges from the sky islands, creating a ribbon of life as it flows from the forested highlands through the lowland grassland prairies. The river basin is a critical site for over 400 species of migratory birds and a wildlife corridor for 80 species of mammals. The extensive grasslands surrounding the San Pedro River are some of the best preserved in the region and harbor species such as the black-tailed prairie dog and Mexican gray wolf. Unique freshwater pools known as ciénegas occur within these grassland prairies and support native fish and amphibian species including the Gila chub and Huachuca tiger salamander.

In the northwest corner of the state, the Colorada River Delta forms one of the largest hydrographic basins in North America and has emerged as a key stopover site on the Pacific Flyway for migratory birds.

The biological diversity of the Sonoran Desert and Grasslands region is threatened by the introduction of invasive species, incompatible cattle ranching and agriculture, road and infrastructure development, ground water depletion, mining, sand and rock extraction, catastrophic fires and fire suppression, logging, illegal hunting and destructive recreational activities.

What the Conservancy is doing
Through its partnership approach and site-based conservation work, The Nature Conservancy is protecting the lands and waters that support life in the following priority areas:

San Pedro River Basin: Conservationists on both sides of the U.S.-Mexico border have been working with private landowners to revitalize the San Pedro River, its tributaries and watersheds. The Conservancy is also developing a protection strategy for privately-owned lands in the San Pedro basin with a landowner network and a long-term capital fund for conservation easements, a conservation buyer program and land acquisition. As part of this strategy, the Conservancy and its Mexican partners purchased the 10,000-acre Rancho Los Fresnos property in January 2005 containing high quality grasslands and ecologically important ciénegas. A research station will be established on the site and prescribed burns will be implemented to re-introduce a natural fire regime in the region’s grasslands.

Colorado River Delta: Overallocation of Colorado River water, urban sprawl and irrigation have reduced the delta to a fragment of what it once was. In collaboration with several conservation groups, the Conservancy is seeking to purchase water rights along the Colorado River in Mexico to partially restore its flow into the Gulf.

El Pinacate Biosphere Reserve: The Conservancy is striving to protect this pristine and biologically diverse volcanic region through conservation efforts including monitoring and controlling the spread of invasive species and developing low-impact ecotourism programs.