For nearly four decades, a team of ecologists and biologists have monitored 60 common flower species in 30 Colorado Rocky Mountain meadow plots. The scientists observed that more than two-thirds of Rocky Mountain wildflowers bloom earlier, peak sooner or continue blooming later in the year compared to the 1970s.

Together these changes have extended the flowering season from late April through late September. Forty years ago, the blooms used to last only from late May through early September.

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“The flowering season is about one month longer than it used to be,” Amy Iler, study co-author University of Maryland biologist, said in a press release, “which is a big change for a mountain ecosystem with a short growing season.”

Millions of flowers bloom in unison during the spring peak, which occurred five days sooner per decade during the past 39 years of observations in the Rocky Mountains of Colorado. More than one-third of the plants now peak sooner in spring and the peak is spread out over more days. The Proceedings of the National Academy of Sciences published the results of the study.

The earlier, longer, less-intense peak may be disrupting animals’ yearly patterns as well. For example, hummingbirds time their nesting so that their eggs will hatch during the spring peak’s bounty of nectar. Now, the hummingbird hatchlings may be out of sync with the peak or supply of nectar may be smaller.

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The first spring blossom burst six days earlier per decade in the long-term study. Approximately half of the alpine flowers now open their first blossoms earlier. The last flowers of the fall bloomed three days later per decade.

Beyond timing, the wildflowers have altered their life cycles in complicated ways. Also, flowers that used to bloom at the same time may now be out of sync. Others may now flower in unison that didn’t before.

These changes may be rippling out to affect the lives of other animals, like the hummingbirds, and plants in Colorado’s alpine meadows.

IMAGE: Yellow wildflower. In the background Mount Mestas (3,528 metres), Rough Mountain on the right. (Wing-Chi Poon, Wikimedia Commons)