Beetles and Butterflies
The temperate forests of the Sierra Madre del Sur are an unparalleled center of endemism and biodiversity in Mexico. Many of the 350 species of orchids in this region can be found nowhere else in the world. The same is true for many other species of plants, birds, mammals, amphibians, reptiles, and insects such as beetles and butterflies. This is one of the richest areas in butterfly species in the Mexican Pacific, with more than 160 species including the Pacific dotted-blue and Pacific orange tip butterflies. The mosaic of forest types in this ecoregion contributes to its astounding diversity. Nearly half of all the species here live in the montane or cloud forests regions, high in the steepest and most inaccessible parts of the mountains where undisturbed habitat is plentiful. Other unique species live in oak and pine forests, including a diversity of shrubs and herbaceous plants and forest creatures such as flying squirrels, pocket mice, and thrushes.
Steep mountain slopes and high humidity characterize the Sierra Madre del Sur pine-oak forests.
Several types of forests grow in this ecoregion: oak forests grow at 6,200-8,200 feet (1900-2500 m) ; cloud forests grow at 7,500 feet (2300 m.); pine-oak forests grow at 7,900-8,200 feet (2400-2500 m); and fir forests grow above 9,800 feet (3,000 m).
In the pine-oak forests of Sierra Madre del Sur, southern flying squirrels soar between trees. A bounty of colors fills the canopy, with plentiful orchids, mosses, and lichens. Scurrying on the rich forest floor below, the Mexican spiny pocket mouse collects seeds. The forest is filled with a chorus of sounds from birds such as white-throated jays, ruddy foliage-gleaners, oaxaca hummingbird, and russet nightingale-thrushes. Collared towhee move about the scattered pine trees, scratching on the ground for food, and amethyst-throated hummingbirds hover above the flowers of shrubs on the forest floor.
Cause for Concern
Many portions of this ecoregion remain intact because they occur on very steep slopes that are inaccessible to humans. However, the region does face growing threats from expanding logging and agriculture in the easier-to-get-to areas. Logging and agriculture, as well as road openings severely damage the native forests and their unique biodiversity. Once forests are cleared, they are often invaded by exotic grasses. And livestock from nearby ranches and farms outcompetes and displaces native mammals. Cattle and other livestock also compact soils, which changes plant structure, often favoring nonnative species, as well as preventing tree seedlings from growing. Coffee and citrus plantations have been expanding considerably in the last decade. Another growing problem is game hunting of wildlife such as paca, deer, tapir, and monkeys for game meat, and the hunting of predators (ocelot, puma) to protect stock.
For more information on this ecoregion, go to the World Wildlife Fund Scientific Report.All text by World Wildlife Fund © 2001