Reserva de la Biosfera Bahía de los Ángeles, a biosphere reserve for the Bay of Los Angeles, is more than 958,000 acres along Baja's Gulf of California coast about 280 miles south of the border. It includes beaches, cliffs, coastal wetlands and bays, and the marine area surrounding Isla Angel de la Guarda, and supports a complex food chain of cold-water corals, pelagic fish such as sardines and anchovies, migratory halibut and yellowtail, endangered whale sharks, sea turtles, dolphins, fin and killer whales and huge seabird colonies.

Valle de los Cirios, a national protected area for flora and fauna (Area de Protección de Flora y Fauna), includes one of the few remaining wild shorelines on the Pacific Coast in North America, and a lot more -- a total of more than 6 million acres spanning the midsection of the Baja Peninsula. It starts about 200 miles south of the U.S. border and stretches 160 miles farther south to the Baja California-Baja California Sur border, and is known for undisturbed bays, sandy beaches, wetlands, rocky reefs and headlands.

Isla Guadalupe biosphere reserve is 160 miles off Baja's Pacific Coast, about 240 miles south of the border. The 98-square-mile, 22-mile-long volcanic rock island draws the world's largest seasonal population of great white sharks and is also a refuge for sea lions and seals. It also has a large endemic plant population.

Islas del Golfo de California, a national protected area of flora and fauna, includes 244 scattered islands in the Gulf of California, stretching nearly 870 miles from the Colorado River Delta on the north to the Islas Marias biosphere reserve in the state of Nayarit on the south. One of the World Wildlife Fund's 200 globally most important ecoregions, it has Sonoran Desert vegetation on its north end, and tropical and subtropical deciduous and mangrove forest on the south end.

Isla San Pedro Mártir, a biosphere reserve in the Gulf of California, is a 75,000-acre island featuring coral forests, eight marine bird species, sperm whales, and one of the largest sea lion reproductive colonies in the Gulf of California.

Sonora

Reserva de la Biosfera El Pinacate y Gran Desierto de Altar, about 1.76 million acres, features an expanse of sand dunes that are up to more than 600 feet tall, and nine extinct volcanic craters up to more than a mile wide, 400 cinder ash cones, petrified lava flows and pockets of lush desert vegetation. U.S. astronauts trained in the Pinacate in the late 1960s to prepare for landings on the moon.

Alto Golfo de California y Delta del Río Colorado, a biosphere reserve in the Upper Gulf of California and Colorado River Delta, has nearly 2 million acres of largely remnant wetlands and brackish water marshes that provide habitat for migratory birds, both land and water species.

Ajos-Bavispe, a national forest and wildlife refuge totaling 456,382 acres, in the Sierra Madre, was established more than 70 years ago to preserve eight "Sky Island" mountaintops -- high-elevation, high-biodiversity communities separated by deserts and grassland valleys.

Sierra de Álamos-Río Cuchujaqui Área de Protección de Flora y Fauna is 330,000 acres of private land, designated a protected area in 1996 because it has southern Sonora's tropical deciduous forest. It lies east of the town of Alamos and includes forested peaks of the Sierra de Alamos and the 23,000-acre Rancho Ecológico Monte Mojino, which was bought by a San Diego-based group called Nature and Culture International and is managed by a local nonprofit, Conservacionistas de Flora y Fauna de Alamos, AC. The Rancho Ecológico provides a higher level of protection -- no cattle grazing -- than the rest of the privately owned property.

Chihuahua

Tutuaca National Protected Area for Flora and Fauna, established in 1937 to protect the headwaters of the Río Yaqui, received little management for conservation goals until the 1990s, and then was upgraded to the "protected area" status in 2001. It's nearly a million acres of mountains and desert sprawling south of the New Mexico border, habitat for rare species whose presence has been documented since the 1990s, including thick-billed parrots and several species of endangered fish. Several conservation organizations, including ProNatura, Monterrey Tech university and CONAFOR (Mexico's National Forestry Commission) have worked with local ejidos to adjust their logging to be lighter on the land and to establish a formal reserve for the parrots.

Médanos de Samalayuca, or the Samalayuca Dunes, totals 156,126 acres and features a large sand dune field, near the U.S. border. It was classified as a natural protected area because it hosts 248 plant and 154 animal species, many of which exist nowhere else. The movie "Dune" was shot here in 1984.

Paquimé or Casa Grandes (Grand Houses) is one of the region's largest and most significant archeological sites and a UNESCO World Heritage site. It contains artifacts from the Paquimé civilization, which settled in Northern Mexico between A.D. 900 and 1340. There's a museum and paths through the ruins of ballcourts and pueblo-style mud-walled condos with T-shaped doorways.

Cañón de Santa Elena is a large Protected Area for Flora and Fauna, totaling about 685,000 acres, just across the border from Big Bend National Park. It features greater biodiversity than its U.S. counterpart, with a larger expanse of high mountains and bigger populations of wildlife, including the Mexican black bear.