May 9, 2012 § Leave a comment
Chihuahuan desert in the lowlands gives way to conifer forest at high elevations. Sky islands in Texas can be seen in the distance.
As the Sierra Madres approach the United States border, their massive, interconnected cordillera give way to a series of broken mountain ranges that are isolated from one another by lowland desert. These “sky islands” rise serenely from the desert and provide a refuge for cool-adapted species and a migratory destination for birds and the humans who seek them out. Biologists have long been fascinated by sky islands for the same reason that oceanic islands have held their fancy since Darwin’s time: they provide a natural laboratory of replicated habitats for the study of evolution. Moreover, each sky island contains altitudinal zonation of habitats, meaning that habitats are stacked one on top of another, beginning at low elevations with desert and culminating with alpine conifer forest. As a result, ecological transitions that would take thousands of kilometers to traverse driving north by car take place over just a few kilometers in sky islands.
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“This is the place where every disparate thread of life is gathered into a single point. Here the acts of humanity do not seem out of place or garishly forceful. This is a thing that humankind has always quietly wished for, a way of living that does not obstruct the path of nature, or even more, is not all that different from it. We want an enduring relationship with our surrounding world. How the land holds up its end of the deal is difficult to describe in a place like this. That here it is a necessity that comes before food and shelter: the barest need of life, to be awakened. ” – Craig Childs