Rancho Los Fresnos and the San Pedro River
Rancho Los Fresnos
© The Nature Conservancy
A cross-border partnership between The Nature Conservancy in both Mexico and Arizona will help to protect the largest and most ecologically important of the freshwater sources of the fragile San Pedro River, flowing from Mexico into Arizona, by 2006.
The Conservancy has been working to protect the entire San Pedro River watershed for 30 years. Moving toward that goal, the Conservancy and its Mexican partners plan to establish a 10,000-acre preserve at a lush and biologically rich site, known as Rancho Los Fresnos.
The Conservancy will assume joint management of Rancho Los Fresnos — with the Mexican nonprofits Naturalia A.C. and Biodiversidad y Desarrollo Armónica (BIDA) and possibly other partners — in July.
The ranch is located at the San Pedro River’s key source south of the international border in northeastern Sonora, Mexico, near Sierra Vista, Arizona. The historic working ranch has been sensitively managed by the same family for generations. The ranch also anchors the largest ciénega, an isolated desert spring or marsh, remaining in the San Pedro River watershed area, and links to one of the largest and highest quality grassland valleys in a region spanning several states and Mexico.
Due to erosion and grassland degradation, the United States has lost 99 percent of its ciénegas. Ciénegas are important to the ecosystem because they absorb excess water from rain runoff and melting snow, hold moisture in drier periods, and help cleanse the environment by mixing nutrients and oxygen into the water. They also filter and neutralize sewage and toxins, while providing nutrient-rich food and a resting place for wildlife.
“The Los Fresnos ranch represents the finest ciénegas habitat that we know of in the San Pedro watershed,” said Holly Richter, upper San Pedro program manager for The Nature Conservancy. “There are species and habitat at Los Fresnos that we’ve long lost in the upper San Pedro basin in the U.S. The ranch is a museum piece, a living history of the habitat that many other parts of the basin used to support.”
“[Los Fresnos] is a museum piece, a living history of the habitat that many other parts of the basin used to support.”
Holly Richter
Upper San Pedro Program Manager
The Nature Conservancy
Northwest Mexico program director Susan Anderson stated, “Because Los Fresnos has been so well maintained for generations by the family who has owned it, the ciénegas are intact.” She added that Los Fresnos grasslands are in better condition than any others in the entire basin of Mexico, providing prime conditions for the largest remaining American pronghorn populations and for grassland birds declining worldwide.
Nearly 400 bird species spend part of their life cycle along the San Pedro. The San Pedro watershed also is home to some 80 species of mammals and more than 40 reptile and amphibian species.
“We’re going to use the ranch as a source of endangered species reintroduction to other ranches in the basin,” Anderson said. The endangered Gila chub, extinct in Mexico for 30 years, and the Huachuca tiger salamander are two critical species thriving on the ranch property. The property will also be used for research, a demonstration site for sustainable ranching, and an example of grassland and riparian (streamside) restoration.
Findings from Los Fresnos will be broadly applied, aligning with the Conservancy’s increased global focus, Richter explained. “It’s essential from a conservation perspective that we continue to think across the fence — and that we think of the San Pedro watershed in its entirety.”
For more information:
- Where We Work: The Nature Conservancy in Mexico
The Nature Conservancy works in partnership with Mexico's conservationists to save its rich natural heritage. Since 1988, The Nature Conservancy has helped protect more than 8 million acres in Mexico.
- Where We Work: The Nature Conservancy in Arizona
For more than 35 years, The Nature Conservancy in Arizona has been working locally with communities, businesses and people like you, providing hope for the preservation of our land, our water, our way of life.
- How We Work: Sustainable Waters Program
The vision of The Sustainable Waters Program is to help protect freshwater ecosystems by advancing water policies that secure adequate water flows in rivers, lakes and wetlands.
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