We’re in the midst of a spectacular autumn season here in the Colorado high country. Autumn in the West is hard to comprehend, even with photography to help, until you’ve experienced it. In the Rocky Mountains of Central Colorado, autumn means shocking blue skies, early snow above 9,000 feet and cascading waves of golden aspen forests. Aspens always steal the show: populus tremuloides otherwise known as the Quaking or Trembling Aspen is the only aspen species native to northern and western North America. The slightest breeze makes the leaves of this ancient tree quake, oftentimes fooling forest explorers into thinking there’s a small creek nearby.

Autumn in the Colorado High Country

Individual aspens can grow to nearly 100 feet and live anywhere from 40-150 years or more. What’s incredible about aspen trees is that they’re all part of the same big organism, connected underground and living for millennia. The largest aspen stand, called Pando, is found in Utah’s Fishlake National Forest. Pando is one of the oldest living organisms on the planet, estimated to be 80,000 years old.

The Transition from Green to Gold – Colorado

As the days slowly get shorter, autumn in the Colorado Rockies starts with a noticeable drop in evening temperatures, followed by the subtle but perceptible increase of yellow in the green summer palette sometime in late August.

Autumn in Colorado

Then, by the first couple weeks of September, adventurers explore forest trails under bright and warm mountain days accented by practically fluorescent colors. Valley temps are still in the 70s, but as the season wanes, colder nights bring the first snows to the upper elevations.

Carpet of Autumn Aspen Leaves

By the end of September/beginning of October, the aspens begin to mellow their tone to a luxurious brilliant gold. On cloudless days, forest explorers experience what Muir described as ambrosial days – warm, golden, sparkling, immortal mountain days with the slightest hint of winter in the wind.

Falling Aspen Leaves – Colorado

Standing in the midst of a sacred aspen stand, autumn wind shaking loose golden leaves that float to the forest floor where I stand, my head tilted up, squinting at the sky – I stand on a carpet of gold beneath my feet. But it doesn’t last long. In a couple short weeks the aspens will be bare, their chalk white trunks contrasting against an indigo sky, waiting for the snow.

Early Snow and Autumn Aspens – Colorado

For those of us who happen to enjoy trekking and sliding through snow, autumn also signals the upcoming winter adventure season. The first time I linked turns through a mature aspen stand on a perfect powder day was transformative.

Aspen Leaves and Early Snow

I don’t want to imagine a world without this amazing tree, but unfortunately North America’s aspens are suffering.

“Quaking aspens (populus tremuloides), an emblematic species of the Rocky Mountains, have seen an abrupt and extensive die-off across large areas of their range, in response to extreme heat and dryness at the beginning of this century. From 2000 to 2010, some 1.3 million acres in the Southern Rockies saw significant aspen decline, and regeneration of new aspens has been much lower than normal. Human-caused global warming is bringing hotter and drier conditions, which not only cause their own effects but amplify those of other stresses.

Autumn Sunset Over Vail Mountain

Although projections have inherent uncertainty, if climate change continues along today’s trends, modeling projections suggest that the climate would become less suitable for widespread, characteristic conifer species such as lodgepole pine, Engelmann spruce, ponderosa pine, and Douglas fir, as well as iconic species including whitebark pine, aspen, and piñon pine. These species could be eliminated from much of their current ranges, potentially changing the fundamental makeup and extent of Rocky Mountain forests.”

-Rocky Mountain Forests at Risk: Confronting Climate-driven Impacts from Insects, Wildfires, Heat, and Drought: September 10, 2014, Union of Concerned Scientists.

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