Window Trail Stop #8

Clouds roll over the mountains and into the Basin

NPS/T. VandenBerg

Quick Facts

Location:

Big Bend National Park

After the end of the most recent glacial period, the climate gradually became warmer and drier. Fossilized evidence in packrat middens near the Rio Grande tells us that oaks and junipers grew along the river about 10,000 years ago. As the climate changed, these plants could survive only in the higher, cooler, and wetter parts of the Chisos mountains, leaving the lowlands to the more heat and drought tolerant species that we see throughout the desert today. Had you hiked to the Window 10,000 to 15,000 years ago, you might have passed through stands of quaking aspen, a tree that in Big Bend is now found only high on the slopes of the Emory Peak. Your walk might have taken you through a woodland of Arizona cypress, ponderosa pine, and Douglas fir, trees whose populations in this region are now limited to the shelter of canyons high in the Chisos Mountains. These plants, and the animals that are similarly “trapped” in this mountain island by unsuitable habitat in the surrounding desert, are called “relict species”.
As you hike the Window Trail, look for some of these remnants from the past including the Mexican drooping juniper, Mexican pinon pine, and numerous types of oaks. Other distinctive plants seen along this trail are mountain laurel, Mexican buckeye, and Texas madrone. Note the mix of mountain species with desert plants. Throughout the Chisos Mountains, it is common to see trees and cacti growing side by side, evidence of continued climatic warming.