The temperature at the base of the mountain was 100 degrees, not unusual for June in Arizona, but hail began to fall in the tiny wetlands called Bear Wallow Spring, at an elevation of 10,500 feet, on the tallest of the sky islands.
The white granulation fell straight down, caroming from the lush green stalks of the corn lily plants, bending the blossoms of the Franciscan bluebells. No trees interrupted the hail because the forest canopy had been incinerated the summer before. Just spruce trunks with peeling bark stood in the circle of the wet, while all around the oasis, the ground was black, and the woods were splintered and charred. Soon the decapitated trees would tip over.
The fire had burned so hot that it had bleached and split the rocks and strewed their fragments like seashells on black sand. Nothing was alive but spiders—everywhere spiders hauling their egg cases in and out of holes in the ashes. Yet within the magical ring of Bear Wallow Spring (magical to the Apache who used to drink here), hip-high spruce and fir prepared to recolonize the peak of this sky island.
Sky islands is the popular term for a dozen disconnected mountain ranges in southeastern Arizona. A few of the ranges spill over into New Mexico, and others are located south of the border. Ecologists refer to the archipelago of mountains as the Madrean Archipelago; the U.S. Forest Service knows them as parts of the Coronado National Forest. Arising from the Sonoran Desert, the cactus sea that links them, each range has its own biological personality. But they all burn by the same rules.
Physical separation has caused their flora and fauna to diverge. Like the finches observed by Darwin in the Galápagos Islands, genetically distinct subspecies of squirrels, lizards, ants, and lichens have evolved on different outposts. Other differences are due to latitude. For instance, the crest of the Pinaleno range, where the 2004 fire occurred, hosts Engelmann spruce and cork-bark fir, a combination found also in Alaska. The trees are a relic population from the Ice Age. You won't find cork-bark fir at the top of the Chiricahua Mountains, 50 miles farther south. Conversely, neotropical hummingbirds and Apache pines, to name some Chiricahua species, aren't seen in the Pinalenos. Large animals like black bears, cougars, and bighorn sheep used to migrate between the mountain ranges, but human development has cut off their corridors and reinforced each range's biological isolation. As a result, most of the natural action in the sky islands takes place in the vertical dimension, including the action of wildfires.
