Sky island ecosystems: What are they?

Earth’s climate is changing, and scientists climate change will affect the unique mountain wildlife in what they call the sky island ecosystems of Arizona’s Santa Rita Mountains. Dr. Adrian Quijada-Mascareñas, an ecologist at the University of Arizona, studies the wildlife in these ecosystems. He told EarthSky that Arizona’s Santa Rita Mountains have some of the world’s best examples of sky island ecosystems.

Sky islands are what we scientists call the ecosystems on mountaintops, when those mountains are surrounded by valleys with completely different ecosystems. When I say ecosystem, by the way, I just mean all the things living and interacting in these places – the reptiles, the birds, the rocks, the weather, the trees – how they all interact.

He said these ecosystems are susceptible to climate change.

When climate warms, surrounding desert regions will creep onto these islands, and change what’s living up there.

To measure how climate change is altering these Arizona mountain ecosystems, Quijada-Mascareñas has been monitoring the population size and genetic health of three species of lizard that live in the Santa Rita range. They don’t live anywhere else, he said. They’re specially adapted to the local scene.

I’ve been monitoring the decline of three different species of lizard. I’ve been able to spot this population decrease using DNA and genetic info collected from the lizards. One species of lizard is already endangered, and looks like it might be headed for extinction.

Quijada-Mascareñas added that reptiles, and also amphibians, are particularly responsive to changes in the environment. He said the lizards he’s monitoring are not quite like the proverbial canaries in a coal mine, explaining that reptiles are less sensitive than amphibians to changes in their environment. Nevertheless, he said, lizards are important to study because they’re what you might call sentinel species:

Their population is on the decline, because of climate change. What’s happening to them will happen to other species, too, across these mountaintops and across the world.

When asked for the most important thing he wanted to tell people, Dr. Quijada-Mascareñas said that biology doesn’t have borders. Climate change doesn’t recognize state or national divisions. Everyone is going to be affected, in some way.

Mexico is one of the hotspots in biodiversity. It’s where I’m from – near the Sierra Madre mountain range. The Sierra Madre mountains extend all the way from Mexico to Arizona. Sky islands are a part of that. Whether the lizards are here or there, they’re all being affected by what’s happening with the world’s changing climate.

Dr. Quijada-Mascareñas said that research is ongoing in the sky islands of Arizona’s Santa Rita Mountains, with scientists trying hard to understand how Earth’s changing climate is affecting mountain wildlife.