Meet the Peloncillo Mountain region: Diverse, Remote, and Intact

  • 3000 mi2 (7,770 km2); Approximate acreage: 1,923,000
  • Crossroads of four states and two countries (New Mexico, Arizona, Chihuahua, Sonora)
  • Habitats ranging from playas and desertscrub (from 4,000 ft/1,220 m) to montane forest (up to 8,600 ft/2,600 m)
  • Three main mountain ranges and three high grassland valleys
  • Part of the Madrean Sky Island Archipelago province and at the intersection of four major biomes
  • A Rare and Wonderful Place:

    Outstanding Features
  • Basin-and-Range topography includes relatively high mountains and three high-elevation alluvial valleys.
  • Origin of substrate is largely volcanic, but with diverse sedimentary elements.
  • Region sits within the Continental Divide’s lowest dip between Alaska and southern Mexico; flora and fauna “leak across” to blend western and eastern elements.
  • Fire has been a crucial driver of ecosystem change in the Peloncillo region.
  • Attention to soil types, fire, hydrology, and foodweb dynamics is crucial to successful restoration of species and habitats.
  • The Peloncillo Mountains and its surrounding valleys, ranges and drainages anchor the center of the Sky Island region—a region of the southwestern United States and northwestern Mexico characterized by isolated mountain ranges separated by desert and grassland. The Peloncillo region is in a unique geographic position that has shaped its rich natural and cultural heritage. It straddles the Arizona and New Mexico boundary in the United States, crosses the international boundary and straddles the Sonora and Chihuahua border in Mexico. The Boundaries of six major biological provinces meet here creating one of the most biologically diverse and productive areas in North America. This region is a sanctuary for many rare, threatened and endangered species and is an important corridor for wildlife movement and migration.

    For the last 13,000 years, this important area has supported a variety of human cultures ranging from people hunting giant ancient mammals to modern day cattle ranchers. The overlap of distinct cultures for thousands of years has shaped the region’s cultural heritage, and influenced the way that its modern inhabitants view and utilize the land. Today, despite human population growth, human development of the landscape, and human use of the land to sustain livelihoods, the Peloncillo region remains an amazingly intact and functioning landscape.

    The greater Peloncillo region includes the Peloncillo Mountains, the Chiricahuas, the Animas Mountains and valley to the east, the San Simon Valley to the west, and the San Bernardino Valley and San Luis mountains to the south. The total land area within this region is roughly 3,000 square miles (7,700 square kilometers)—about the size of Yellowstone National Park. Watersheds include drainages that flow into the San Simon Valley and then north into the Gila River, those that flow from the southern Peloncillo and San Luis Mountain area south into the Río Yaqui system, and those that flow into the closed basin of the Animas Valley.

    Chiricahua-Peloncillo Region
    The Chiricahua-Peloncillo Region

    Six otherwise distinct biological provinces overlap and intergrade in the Peloncillo region. Many plant and animal species characteristic of the Rocky Mountains reach their southern extent here, and even more species from Mexico’s Sierra Madre reach their northern limit. Although the Peloncillo region lies within the bounds of the Chihuahuan Desert, elements of the Sonoran Desert infiltrate from the west, and some characteristics of the Great Basin and Great Plains appear as well. For example, the Animas Valley, between the Peloncillo Mountains and the Animas Mountains to their east, is considered the southwestern most extension of the Great Plains.

    The floral and faunal diversity produced by the mix of these provinces is enhanced by the basin and range topography of the area—long, north/south oriented mountain ranges separated by valleys. These isolated mountain ranges of southwestern New Mexico and southeastern Arizona are referred to as “Sky Islands,” since in their upper, cooler and wetter elevations they support an assemblage of plants not found in the valleys below. Thus within a very short linear distance one can find desert-adapted species such as cacti, mesquite trees, and creosote bushes, then montane species such as oaks, junipers, and pines. Also notable in the mix of Peloncillo habitats are several remarkably intact riparian corridors largely free of invasive plant and animal species.

    A final element affecting diversity in the Peloncillos lies in a twist of continental topography. The long spine of the Continental Divide, stretching from British Columbia to Central America, reaches its lowest point at several passes in the Peloncillo region. These passes allowed “leakage” of plant assemblages otherwise blocked by high elevations. For more information read full report here -- Natural Heritage of the Peloncillo Mountain Region (PDF)