The Madrean Pine-Oak Woodlands are found at higher elevations in the mountain ranges of Mexico, Arizona, New Mexico and Texas. Characterized by “sky islands” these pine forests, high in biodiversity, are surrounded by radically different habitats in the lowlands. Mostly tropical and subtropical deserts, dry shrublands, and grasslands. Ecotourism to visit the hotspots numerous birds, magnificent monarch butterfly display, and other unique areas can be a major support for conservation in this area.
ECOLOGY OF MADREAN PINE-OAK WOODLANDS
The consistent pine and oak canopy as well as other similarities in the plant and animal communities are what gives the hotspot its cohesive character. The hotspot reaches across significant north-south latitudes. This combined with significant variation in climate, soil types, orientation of slopes, and geologic history also makes it a hotspot with varied ecological character.
Most of this hotpot lies within Mexico, with isolated patches occurring further north in the southwestern United States. The Madrean Pine-Oak Woodlands Hotspot includes the main mountain chains of Mexico: the Sierra Madre Occidental (including the Madrean Sky Islands of southern Arizona and New Mexico), the Sierra Madre Oriental, and the Trans-Mexican Volcanic Belt, the Sierra Madre del Sur, and the Sierra Norte de Oaxaca, as well as isolated mountain tops in Baja California (particularly around the Sierra de la Laguna).
Mexico is considered an important center of diversity for Pines and Oaks and has the highest diversity of pines of any country in the world. It also have between 135-150 species of oaks, many of which are found nowhere else in the world.
The Madrean Pine-Oak Woodlands enjoy an astonishing richness of species. Conservative estimates put the number of flowering plants in the pine-oak forests at 5,300 while 2,000 species of native plants in the Madrean Sky Islands.
Around 525 bird species, 23 of which are strict endemics occur in this hotspot. Four of BirdLife International’s Endemic Bird Areas (EBAs) overlap with this hotspot. Species such as the thick-billed parrot, Sierra Madre sparrow, and the imperial woodpecker are attractions for any birdwatcher.
This hotspot is home to one of the most spectacular wildlife wonders in the world: the overwintering of monarch butterflies in the pine forests of Michoacan. Each fall, about 100-500 million monarchs migrate south from eastern North America to form giant clusters on the branches and trunks of trees in the oyamel fir ecosystem.
There are 328 species of mammals present in the hotspot. The iconic volcano rabbit or zacatuche is endemic to the Trans-Mexican Volcanic Belt. One of the smallest and most unusual rabbits, it has small, round ears and utters high-pitched, penetrating vocalizations. The zacatuche relies on the zacaton bunchgrass for its survival. It constructs the entrance to its burrow at the base of a clump of bunchgrass and prunes the plants so they form a thick roof for protection. The zacatuche only lives in the Trans-Mexican Volcanic Belt surrounding Mexico City. The rabbit is a foundation species, efforts to save it will benefit the entire habitat and the species that live within it. Others wildlife includes a high density of American Black Bear, a surprising diversity of fish unexpected in the high altitude character of the area, amphibians, reptiles, and birds.
Cave Creek Canyon in the Chiricahua Mountains of southeastern Arizona the elegant trogon attracts flocks of birders. This species range matches closely that of the Madrean Pine-Oak Woodlands Hotspot, including the sky islands of the northern extension. This area also harbors more species of hummingbirds than anywhere else in the United States. The sky islands are isolated mountain tops surrounded by radically different lowland environments. The unique biodiversity of animal and plant life on the sky islands make them a hotspot for ecotourism and an important consideration for conservation.
The Madrean Pine-Oak Woodlands Hotspot is also an important center of cultural and ethnic diversity. Among the ethnic groups in the region are the Chinantec, Cora, Cuicatec, Mazatec, Mixe, Mixtec, Nahuatl, Popoluca, P’urhepecha, Tarahumara, and Zapotec. In Mexico, the natural resources of over half the national lands are under the control and use of indigenous peoples. Indigenous communities also reside within the country’s natural protected areas. (Hotspots Revisited)
Pines and to a lesser extent, oaks, are very important in the Mexican logging industry. Legal and illegal logging is on the rise in many areas. Non-timber products such as lichen for Christmas ornaments and mushrooms for cooking are also unsustainably extracted.
Naturally occurring fires alter the habitat, but intentional burning has also increased to make room for livestock grazing and other agricultural purposes. In southern Arizona, fire has been suppressed for almost a century by federal and state agencies now leading to high levels of fuel on the ground. As a result, Arizona has experience some of the largest wildfires in recorded history in the last 10 years. The higher elevation forests have also changed from open ponderosa pine forests to dense stands of mixed conifers apparently due to fire exclusion.
Deforestation, wildlife poaching, plant collection, fire, clearance for agriculture, road and tourist development, overgrazing, and intensive urbanization threaten the rare and endemic biodiversity throughout this hotspot.
The unique “sky island” character of this hotspot also makes its biodiversity especially susceptible to climate change as species have limited habitat range and the inability to migrate once the upper altitude of their range is reached.
Only 6% of the hotspot is under some form of official protection. Among the more important protected areas in the hotspot are:
- Monarch Butterfly Biosphere Reserve in Michoacan. It conserves different types of vegetation including pine, pine-oak, and juniper forests.
- Sierra de Manantlan Biosphere Reserve in Jalisco with diverse pine-oak forests containing 33 species of oak.
La Primavera Forest Reserve
- National Parks: Nevado de Colima, Navado de Toluca, Iztaccihuatl-Popocatepetl, Cofre de Perote, Pico de Orizaba in Veracruz
- The largest protected area in Mexico – Cumbres de Monterrey National Park
Big Bend National Park in Texas, the largest protected area in the hotspot
- The Madrean Sky Islands are afforded some protection in the U.S. by the Forest Service, private land holding of The Nature Conservancy, U.S. National Monuments and Wilderness Areas
A number of conservation NGOs are working in the region
- Fondo Mexicano para la Conservacion de la Naturaleza is working on fire prevention strategies in the butterfly sanctuary.
- PRONATURA NORESTE conserves and promotes sustainable use of natural resources in northeast Mexico and runs reforestation programs in thick-billed parrot habitat and communities affected by forest fires
- The Sierra Madre Alliance is a support network of Mexican and international groups working to preserve biodiversity and forest ecosystem functioning in pine-oak forests
- The Sky Island Alliance, a U.S. organization, works with partners in Mexico to preserve the sky islands unique to this hotspot. It works with the Nature Conservancy, Audubon Society, U.S. Forest Service and private reserves for conservation goals.
Russell Mittermeier, et al. (2004). Hotspots Revisited. Cemex.
Header Photo by BAlvarius – Own work.
Licensed under CC BY-SA 4.0 via Commons