Study: Early wildflower blooms sign of a warming Wyoming

A WyoFile story by by Dustin Bleizeffer

JACKSON HOLE, Wyo. — Wyoming botanist Trevor Bloom spotted his first springtime blooms of the year on March 28. Bloom, while tracing the footsteps of famed ecologist Frank Craighead at Blacktail Butte in Grand Teton National Park, saw the orogenia linearifolia, or snowdrop, wildflower.

“I don’t think I’ve ever seen a wildflower, besides a dandelion, flowering in March,” Bloom said. The snowdrop bloom was nearly a month earlier than Craighead had recorded in the 1970s. “It means we’re probably going to have a very early spring this year. It probably means that we’re going to have very low water levels, and we’re probably going to have an increased risk of wildfire this year.”

The prognostication isn’t merely a gut feeling. Bloom and co-authors Donal S. O’Leary and Corinna Riginos recently published the study “Flowering Time Advances Since The 1970s In A Sagebrush Steppe Community” in the journal Ecological Applications. The study — a project of The Nature Conservancy in Wyoming — shows that early blooms of wildflowers correlate with warming average temperatures and a host of potential ecological responses.

The team began measuring plant behavior in 2016, in the exact locations where Craighead documented seasonal rhythms and relationships between plants, insects, birds and animals — the basis for his 1994 book “For Everything There Is A Season.” Bloom and his co-authors wanted to learn how closely the ecological relationships that Craighead observed track with what’s happening decades later.

They learned the seasons themselves are changing — particularly springtime, which is arriving sooner in Wyoming and potentially driving a cascade of ecological changes.

“We found that early flowering species had the greatest shift, moving up to three weeks earlier,” Bloom said. “Mid-summer flowers, like lupines, are flowering on average about 10 days earlier, and then late-summer flowers — like fireweed and goldenrod — have actually not changed significantly at all.”

Early flowering and earlier production of fruits correlate with warming average temperatures in Wyoming and throughout North America, Bloom said. Wyoming’s annual mean temperature increased 2.2 degrees Fahrenheit from 1920 to 2020, according to National Oceanic and Atmospheric Administration data. One of the most significant responses to warming average temperatures in Wyoming is early snowmelt and spring runoff.

Wyoming’s warming springtime, and ecological responses to it, have major implications for all manner of vegetation and wildlife — from whether migrating hummingbirds might find nectar at their annual stops to when bears go into and emerge from hibernation.

“This is just a very tangible example of climate change,” Bloom said.

‘For everything there is a reason’

Bloom grew up in Jackson idolizing brothers Frank and John Craighead — famed naturalists and conservationists credited for groundbreaking methods for studying grizzlies and other wildlife in and around Yellowstone National Park.

“I was inspired by them as these ecologists who were also adventurers and mountain climbers and just really inspirational people,” said Bloom, who serves as community ecologist for The Nature Conservancy.

“Frank Craighead became very interested in phenology, which is the seasonal timing of ecological events,” Bloom said. “It’s [studying] when snow melts, when flowers bloom, when they go to seed and the interaction of animals; when the elk begin to migrate, what they’re feeding on at what times, when bears emerge from hibernation, when birds migrate from the south. Those are all examples of phenology.”

The Craighead family homestead near Blacktail Butte, just outside the Grand Teton National Park boundary, served as an intriguing landscape to document the rhythms and interactions of a complex sagebrush steppe ecosystem. For several years in the 1970s and 80s, Frank Craighead recorded weekly observations along a 1.7-mile route from the base of Blacktail Butte toward its summit, documenting hundreds of plant, insect, bird and animal species.

Many professional and amateur ecologists refer to “For Everything There Is A Season” as a field guide to learn about seasonal interactions in the region. Corinna Riginos, director of science for The Nature Conservancy, used to ask students at the Teton Science School whether their own observations matched those described in the book. She began to notice seasonal events that Craighead described weren’t quite in sync.

A passage from Craighead’s book came to mind: “If the event occurs earlier or later than anticipated from the base data provided in the book, you can try to determine the influencing factors — for everything there is a reason.”

Riginos proposed continuing Craighead’s work to identify potential trends from the 1970s to today, factoring in changing climate conditions. The Nature Conservancy team consulted with Craighead’s widow and son to confirm his route and the plots where he’d made his observations. They were even given access to hundreds of pages of Craighead’s handwritten notes.

“Some of them are in cursive and in journals, and some of them have burned edges and are smoke-stained because his cabin in Grand Teton National Park burned down,” Bloom said.

The notes added a new dimension to “For Everything There Is A Season,” establishing a critical baseline to inform The Nature Conservancy’s research.

The findings

The greatest degree of change was measured among wildflowers known to bloom just as spring snowmelt begins, such as the snowdrop and hooded phlox. Those and other early spring flowers bloomed an average 17 days earlier compared to Craighead’s data from the 1970s and 80s, according to the study. Some bloomed 36 days earlier, based on the study’s 2016-19 data.

Mid-summer flowers bloomed an average 10 days earlier, and berry-producing shrubs five days earlier.

While early blooms are a logical, natural response to a warming climate and changing hydrological conditions, they pose significant challenges for wildlife that depend on them. Hummingbirds, for example, base their migratory habits on the length of daylight, which means they might arrive at annual stopover sites after flowers have lost their nectar.

“The flowers might be all dried up and gone,” Bloom said, adding that the phenomenon also threatens to extend the wildfire season.

If bushes continue to produce berries earlier in the season, it could result in food scarcity for bears in the fall. “There’s a direct correlation between the size and the abundance of a berry crop and bear-human conflicts,” Bloom said.

Better understanding these types of “phenological mismatches” is critical to inform land and wildlife managers about how to help mitigate potential threats, Bloom said. Preserving large, intact landscapes is especially critical for sagebrush ecosystems.

“You want to preserve as much biodiversity of plants as possible,” Bloom said. When restoring disturbed surfaces, it’s important to tailor a seed mix to include both early and late-blooming wildflowers. Bloom and The Nature Conservancy are consulting with Grand Teton National Park officials on such an effort at the Kelly hayfields, he said.

The study also highlights the need to maintain connectivity and corridors between seasonal habitats. Pronghorn, deer and other migrating wildlife must adapt to changing seasonal patterns to take advantage of vegetation as it “greens up” — a message underscored by the work of the Wyoming Migration Initiative.

Bloom said he’s excited to continue the wildflower research and to trace the footsteps of Craighead. The Nature Conservancy plans to expand its phenology research to other areas of the state. The work is bolstered by the organization’s Wildflower Watch initiative, which taps citizen volunteers to contribute phenology observations in northwest Wyoming. Some 700 volunteers have contributed to the program.

“Our goal is to increase people’s understanding of native plants, increase their understanding of invasive plants and form personal connections with climate change in Wyoming,” Bloom said.