Our world, filled with a diversity of life and ecosystems is perhaps undergoing a new mass extinction, produced and conducted by exploitation and expansion. Consequently, regions of the earth have been marked into hotspots, spanning regions of vast biological diversity, but under the threat of humans. One such hotspot is the Madrean Pine-Oak Woodlands in Mexico and Southern United States.
The Madrean Pine-Oak Woodlands hotspot includes Mexico’s main mountain chains, namely the Sierra Madre Occidental, the Sierra Madre Oriental, the Trans-Mexican Volcanic Belt, the Sierra Madre del Sur, and the Sierra Norte de Oaxaca, as well as isolated mountaintop islands in Baja California (particularly around the Sierra de la Laguna). Although the vast majority of the hotspot’s 461,265 km² lie within Mexico, a few scattered patches occur in the southern United States (represented by the Madrean Sky Islands, a series of about 40 mountain-tops in southern Arizona and New Mexico). The complex geological history of the Madrean Pine-Oak Woodlands is evidenced by its rugged mountainous terrain, high relief, and deep canyons. The Trans-Mexican Volcanic Belt, which runs from west to east across central Mexico, and serves as a bridge connecting the Sierra Madre Occidental and the Sierra Madre Oriental, is the highest mountain chain in the hotspot, including the peaks of Pico de Orizaba (5,747 meters) and Popocatépetl (5,452 meters). The climate of the hotspot is primarily temperate, with annual precipitation varying between 500 and 2,500 millimeters, largely depending on slope and aspect.
A quarter of all Mexico’s plant species are found here, many of them found nowhere else on Earth. The pine forests of Michoacán provide famous overwintering sites for the annual migration of millions of monarch butterflies. Unfortunately, the destruction of pine forests due to excessive logging is the leading cause of habitat loss in this region. The pine-oak woodlands are composed of stands of oak (Quercus), pine (Pinus), douglas-fir (Pseudotsuga) and fir (Abies). Pine and oak forests are the characteristic vegetation type in the hotspot, ranging from monospecific stands of either pines ( Pinus) or firs ( Abies) to almost pure stands of oak ( Quercus). In between these two extremes, different regions have varying combinations of species, with some more dominant than others. The pine-oak woodlands have an insular-type distribution by virtue of being surrounded by more extensive floristic provinces, generally tropical or arid. This feature is particularly noticeable in the northern Mexican Highlands and the Madrean Sky Island Archipelago. The World Wildlife Fund recognizes several distinct pine-oak woodlands ecoregions, based on geographic distribution and species mix.
Hope for the Madrean Hotspot
The vast majority of the hotspot lies in Mexico’s main mountain chains with outlying mountaintops in Baja California and the Southern United States. Estimated at 461,265 km2, only some 27,000 km2 is under some form of protection, while 8,900 km2 are in protected areas in IUCN categories I to IV. The International Union for Conservation of Nature (IUCN) has categories that determine how a certain area is managed and protected.
The Madrean Pine-Oak Woodland area is somewhat protected up to about six percent; the IUCN only protects around two percent. Endemic terrestrial vertebrate species, located on the slopes of Sierra Madre Del Sur are unprotected. The Moarch butterfly Biosphere Reserve in Michoacan is an important protected area that preserves the migration of monarch butterflies.
The hotspot in Southern United States has protection operated by private owners such as The Nature Conservancy. Other private owners are designated as U.S. National Monument or U.S Wilderness Area protectors. A network of Mexican and international partners called the Sierra Madre Alliance work to preserve the biodiversity of functioning forested ecosystems via local participation. One particular company, Cemex, a cement company that has bought land within the Madrean Pine-Oak Woodlands, has taken the expansion of the protected land all the way to to the Big Bend national park in Texas. CEMEX has successfully protected the lands it has bought.