SKY ISLANDS CONSERVATION
In the southwestern United States and northwestern Mexico lies a region boasting the highest biodiversity in inland North America. Isolated mountain ranges topped by 10,000-foot peaks rise from intervening desert valleys and grasslands, prompting the nickname “Sky Islands.” A unique array of geographic, topographic and climatic influences create a bewildering variety of plants and animals here, many imperiled or found nowhere else.
Also called the Madrean Archipelago, dozens of distinct mountain ranges scattered on both sides of the U.S.-Mexico border function as high-country stepping stones between the subtropical Sierra Madre to the south and the temperate Rocky Mountains to the north. The area also lies along the confluence of the Sonoran and Chihuahuan deserts, two very different ecoregions with disparate plant communities. Dramatic elevation changes result in distinct vegetation zones that can vary from desert scrub to spruce-fir forest in a single range, sometimes within the space of a few miles. Add in the climatic phenomenon of a summer monsoon — a seasonal wind pattern that produces powerful thunderstorms in July and August — and you have all the ingredients for a world-renowned biodiversity hotspot.
Ascending the steep slopes of a Sky Island mountain range, one encounters a series of distinct lifezones, each with its own particular array of plants and animals — from high coniferous forests to the grasslands and chaparral of lower elevations — and a spectacular array of species thrives in the transition zones and microhabitats in between. For example, in the mid-elevation Cave Creek area of the Chiricahua Mountains, research points to the world’s highest diversity and density of nesting birds of prey.
Some species, like the Mount Graham red squirrel, occur only in a single mountain range after evolving in isolation, surrounded by deserts; the red squirrel is just one of about two dozen species endemic to the Pinaleños, the highest of the Sky Island ranges. Various species of talus snails are likewise limited to a single mountain range, including the Rosemont talus snail in Arizona’s Santa Rita Mountains. Such species are particularly vulnerable to threats like large-scale resource extraction and climate change, the latter of which jeopardizes the Sky Islands’ numerous perennial streams, crucial to many species’ survival. The entire home range of the Mount Graham red squirrel is threatened by a single array of large telescopes, while the Rosemont talus snail faces extinction as a result of a single open-pit copper mine proposal.
Many species in the Sky Islands region occur at the northernmost or southernmost extent of their ranges. Endangered jaguars and ocelots, for example, roam into the mountains and canyons of southeastern Arizona and southwestern New Mexico from larger populations to the south. Other subtropical species found in the Sky Islands include the coatimundi, elegant trogon, thick-billed parrot and Mexican garter snake. Conversely, the region harbors the southernmost occurrence of pure spruce-fir forest on the continent.
It’s no coincidence that the Center maintains its headquarters in the Sky Islands; in fact, our founding more than 20 years ago was spurred by efforts to gain federal protection for the Mexican spotted owl, an iconic denizen of the region. Our work to protect this and other Sky Islands species has produced significant — and at times dramatic — land-management changes that have left a living legacy. Over the years, we’ve successfully advocated for listing a number of Sky Island species — including the southwestern willow flycatcher, spikedace, loach minnow and Chiricahua leopard frog — and for the protection of millions of acres of habitat. In the late 1990s, litigation against the U.S. Forest Service (which manages much of the Sky Islands) led to removal of cows from many streams and other changes in management. Based on newly listed species and other new information, the Center recently reinvigorated this suit and hopes to gain further protections for endangered species. In late 2010, we filed a notice of intent to sue the Forest Service to stop habitat destruction harming the iconic Mount Graham red squirrel.
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