Durk didn't have to hang out feeling trapped on this sky island.

We got a feeling, even from the car, of the sky islands' astonishing ecological diversity.

The sky islands exist as a sort of biological Nafta, where national boundaries blur.

It is, of course, the sky islands' ecological fecundity that prompted the museum to establish a research station here.

A trip up to any one of the 27 sky islands shows the ravages of heat on the land.

"The sky islands have existed since the Pleistocene," he said, "and now with these huge fires you stand to lose some unique species."

These isolated ecological systems are known as sky islands.

The populations that live on these sky islands are cut off from each other, and evolve independently.

The mountain range is one of Arizona's sky islands.

This mountain is just one of the many scattered sky islands in the southwest.