ʹappƽ̨

The Spectacular Madrean Sky Islands

On a nine-month trek covering nearly 1,000 miles, an Arizona photographer witnesses the wild biodiversity of the Madrean Sky Islands

  • Text and photos by Deirdre Denali Rosenberg
  • Wildlife Photos
  • Jun 25, 2025

I FIRST HEARD OF THE MADREAN SKY ISLANDS while taking a naturalist course in Tucson, Arizona, in 2023, and I was immediately intrigued. Stretching from southern Arizona and New Mexico into Mexico, this archipelago of roughly 63 independent mountain ranges contains an array of distinct biomes, as the elevation changes from desert floor to subalpine ecosystem. Here, weather from the temperate Rocky Mountains to the north and the subtropical Sierra Madre Occidental to the south collides, producing particular conditions, with each range a microcosm unto itself.

“The Sky Islands are a rich crossroads, where temperate and subtropical species intermix and find refuge among the forested mountains, foothill grasslands and valley deserts,” says , a program director with the conservation group .

This convergence of climates creates one of the most biodiverse areas in the world, according to the U.S. Geological Survey, with unique habitat in every range. More than 7,000 plant and animal species flourish here, including the planet’s northernmost jaguars and smallest owl, the . The Madrean Sky Islands also are home to endemic wildlife, such as the , a federally endangered species that lives only near the top of Mount Graham (10,720 feet) in southeast Arizona’s . The squirrels cannot survive in the extreme desert lowlands and are therefore stranded, so to speak, on their island.

As a conservation photographer, I try to understand as much as possible about the areas where I work. In the Madrean Sky Islands, each range has a specific ecosystem and distinct wildlife, including endangered and endemic species, making them vulnerable to threats such as climate change and human development. As I researched the ranges, I was fascinated to learn that more than half of North ʹappƽ̨’s bird species can be found here and that many of the islands have not yet been fully explored.

To sate my curiosity, I decided to plan a trek that would link multiple sky islands in Arizona via the Sonoran Desert valley floor. My thru-hike would take me nine full months, from February to October 2024; would cover elevation from 2,300 feet to just under 10,000 feet; and would traverse seven Madrean Sky Island ranges and nearly 1,000 miles. The slideshow below highlights some of what I saw.


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