banner image showing wild monkeyflowers
PHOTO: Shayne Estill

Walking with Wildflowers

Gathering phenological data on the Pacific Crest Trail

Plants on the Pacific Crest Trail
PHOTO: Nicholas Kooyers

Thru-hikers on the 2,650-mile Pacific Crest Trail (PCT) are on a mission: walk from Mexico to Canada before snow hits the mountains in northern Washington. To accomplish this goal, hikers must travel 20-plus miles each day, a distance that doesn’t always allow for stopping to admire high-country vistas or flora and fauna along the trail. But last summer, some of these long-distance hikers could be seen pausing, pulling out their smartphones, and recording information about the wildflowers scattered around their feet.

As participants in a citizen science project led by botanists Benjamin Blackman and Nicholas Kooyers, these hikers were gathering valuable data for the pilot of a multiyear National Science Foundation–funded study of flowering plants on the PCT. Their observations will help scientists understand how climate change may be altering plants’ flowering and seed-making behavior, influencing, over generations, their DNA.

The Highs and Lows Of DNA

Blackman, an assistant professor in the Department of Plant and Microbial Biology, has spent his career studying the genetics of how plant adaptation and domestication happen through time.

On the domestication side, Blackman’s research focuses on sunflowers, a domesticated food crop known for its ability to track the sun’s daily movement across the sky. “With domestication, changes in plant shape and physiology happen more quickly than in nature, perhaps in two thousand to ten thousand years,” says Blackman. For sunflowers, domestication occurred over about four thousand to five thousand years, he says. “Domestication is a kind of human-made ‘artificial selection,’ highlighting really big changes that might take much longer in the natural world.”

Ben Blackman
PHOTO: Jim Block

The yellow monkeyflower—Erythranthe guttata, also known as Mimulus guttatus—is the other subject of Blackman’s research, his vehicle for examining plant adaptation as it occurs in the natural world. Thoroughly studied since the 1940s, the monkeyflower is considered a model plant for researchers working to understand how and why plant traits evolve in the wild.

Monkeyflowers can be found at many different elevations—from California’s Central Valley to the high-elevation slopes along the PCT. And it turns out that the plants in these different locales have adaptive differences in their DNA, displaying traits that closely fit the needs governed by their diverse environments across elevations. The plants at snowy high elevations contain DNA that signals for them to wait for longer, summertime days before they start producing buds and flowers. The DNA of the plants at lower elevations, meanwhile, allows them to start budding earlier in the year, when the days are shorter, so they can flower and set seed before the spring rains disappear and the summer heat dries up soil moisture. The life of a monkeyflower at a lower elevation today could offer a preview of what plants at higher elevations might soon face, since climate change will bring shorter spring seasons and longer, warmer, drier summers to all elevations. But how will those high-elevation plants—with their DNA telling them to wait for longer days before beginning to grow and flower—fare when the snowpack starts to melt earlier and the summer becomes hotter, even as the day length remains constant?

This is what Blackman’s lab is working to understand. Using high-throughput genome-sequencing technology, the team looks closely at the DNA of monkeyflowers from various elevations to identify the adaptive genetic differences and provide insight into how the species may adapt as climates shift.

Stopping to Smell the Flowers

With the same goal of better understanding how changing environments will affect plant species, Blackman and Kooyers launched their citizen science project in the wild to monitor the monkeyflower and 19 other plant species at high elevations over multiple years. The involvement of hiker citizen scientists will allow the researchers to collect numerous observations of species at sites in two national parks and one national forest along the PCT each year, resulting in a powerful set of data that they could never obtain alone.

“The steady stream of long-distance hikers offers a wonderful opportunity for citizen science.”
— Benjamin Blackman

The idea to recruit backpacker volunteers first came to Kooyers in 2014, while he was conducting field research on monkeyflowers in Oregon as a postdoctoral researcher in Blackman’s lab. “I was thinking that to really get the kind of data we need, we’d have to survey plant populations on a daily or weekly basis, which isn’t realistic in remote locations,” says Kooyers. “While talking with my backpacker friends—who are extremely passionate about conservation—it struck me that a citizen science project could be the perfect coincidence of motivations.”

“The PCT offers a wonderful opportunity for citizen science, because there’s a steady stream of hikers along the trail throughout the growing season,” says Blackman. “Over time, we hope to crowdsource information about when plants are growing, how that’s changing, and if these changes are correlated with temperature or precipitation.”

To launch their Walking with Wildflowers project in 2018, Blackman and Kooyers partnered with the USA National Phenology Network, which has an extensive database of plant life cycle observations—known as phenology—collected by citizen naturalists nationwide. The database now holds more than 15 million observations from nearly 14,000 amateur naturalists, freely available to scientists, public decision-makers, and natural resource managers. The network’s smartphone app, Nature’s Notebook, allows Walking with Wildflowers hikers to record observations along the trail.

Students in Yosemite scouting observation sites

From left: Jack Colicchio, Shayne Estill, and Nicholas Kooyers stop for a selfie while scouting observation sites for Walking with Wildflowers in Yosemite National Park.

Kooyers and Blackman collaborated with national park and forest service staff members to choose two segments of the PCT for the project. They included one stretch of trail in the southernmost portion of Washington State’s North Cascades National Park and another that starts in Inyo National Forest and continues north into Yosemite National Park. Each of the 15 data-collection sites they selected is home to a subset of the 20 plant species that hikers can observe, including lodgepole pine, yarrow, and, of course, monkeyflower.

While many of the sites are in remote areas, Blackman and Kooyers also intentionally included sites accessible to day hikers. At these, they expect to get many more observations than farther out on the PCT. One of the sites in Yosemite isn’t even on the PCT; it’s near a ranger station that sees heavy foot traffic. “The goal with that site is primarily educational,” says Kooyers. “We want to help visitors understand the basics of our research and the potential consequences of climate change on these plants’ life cycles.”

A site like this, where it’s possible to gather observations from many hikers in one day, is also handy for verifying data reliability. Great variation in a day’s data might point to hikers struggling to make consistent observations. It could also indicate that data collected at other sites is not as trustworthy as researchers would like.

During the pilot summer last year, two test hikers from Blackman’s lab, Jack Colicchio and Shayne Estill, helped evaluate site choices and fine-tune plant-location instructions. They also discussed the program with passing hikers to recruit volunteers and posted flyers on ranger station bulletin boards.

“We want to help visitors understand the basics of our research and the potential consequences of climate change.”
— Nicholas Kooyers

Estill—an undergrad lab assistant who is majoring in molecular and cell biology—completed her first-ever backpacking trip while assisting at the Yosemite and Inyo sites. The trail time helped her solidify her academic goals. “I learned that climate change affects even the smallest organisms,” she says. “Thinking like a researcher has been fun, and this experience encouraged me to continue training to become a scientist.”

Kooyers stresses that sites need to be easy to find, so they’re preferably near a recognizable landmark like a water crossing or a trail signpost. One known as the “lightning spire,” in the North Cascades, is hard to miss; it’s near a 25-foot tree struck dead by lightning.

To find the sites, hikers reference Walking with Wildflowers companion guides that contain maps of each segment, GPS coordinates and photographs of each site, and pictures showing the plants included in the study. Once they locate a site, they look for small metal tags placed at ground level, which identify each plant flagged for the project. From there, the Nature’s Notebook app asks simple questions that guide observers: Does the plant have buds, leaves, or flowers? If yes, how many flowers, how many buds? And so on. These questions help create accurate portraits of a site during each observation.

Walking Into the Future

A young woman pollinating yellow flowers

Undergraduate student Estill pollinates monkeyflowers in a greenhouse on the UC Berkeley campus.

Photo: Jim Block

Even with minimal advertising during the pilot year, 38 hikers participated. They uploaded approximately 2,500 separate plant observations, nearly 1,500 from North Cascades National Park and almost 1,000 from Inyo National Forest and Yosemite National Park.

The Walking with Wildflowers team is analyzing this first-year data set, and Blackman and Kooyers are hoping for many more hikers and observations this summer. Their goal is one hiker checking plants at least once every one to three days at each site. Hiker participants can directly access all the study data through the USA National Phenology Network’s website. And, notes Kooyers, who is now an assistant professor at the University of Louisiana at Lafayette, volunteers will eventually receive research progress updates via a listserv.

Blackman says he once imagined “traipsing around doing research in the mountains or foothills” and then felt the dream come true while he was a postdoc on a three-week trip collecting plant specimens in the Sierra and Cascades. That feeling, he says, has resurfaced with the Walking with Wildflowers project. “I’m doing the exact fantasy project I pictured when I was an undergrad,” he says. “And it’s so exciting to be able to involve a group of citizen scientists in collecting valuable data for the scientific community on the biological impacts of climate change.”

For more details or to get involved in Walking with Wildflowers, visit