Sky islands are isolated mountains surrounded by radically different lowland environments. The term originally referred to those found near the southern borders of the U.S. states of Arizona and New Mexico with the northern borders of the Mexican States of Chihuahua and Sonora such as the Dragoon Mountains featured in this post. The isolation has significant implications for these natural habitats. The American Southwest region began warming up between ∼20,000–10,000 years before the present-day and atmospheric temperatures increased substantially, resulting in the formation of vast deserts that isolated the sky islands.
This sycamore tree survives life in this ephemeral stream of an Arizona “Sky Island” by allowing entire trunks to die off during extended dry spells. The tree is an Arizona Sycamore (Platanus wrightii).
Reference: wikipedia article “Sky Islands.”