Spring is coming, and with it comes the promise of warmer weather, longer days and renewed life.

For residents of the Pacific Northwest, one of the most idyllic scenes of this renewed life is the wildflowers that light up Mount Rainier’s subalpine meadows once the winter snowpack finally melts. These floral ecosystems, which typically arrive in summer, are an iconic feature of Mount Rainier, and a major draw for the more than 1 million tourists, hikers and nature-lovers who visit the national park each spring and summer.

But without cuts to our carbon emissions, by the end of this century, scientists expect that snow in the subalpine meadows will melt months earlier due to climate change. New research led by the 91̽�� shows that, under those conditions, many visitors would miss the flowers altogether.

The research team made this discovery using crowd-sourced photos of Mount Rainier’s subalpine meadows taken from 2009 to 2015 and uploaded to the photo-sharing site Flickr. As they report in a published in Frontiers in Ecology and the Environment, 2015 was an unusually warm, dry year when snow melted and disappeared from the meadows about two months earlier than usual. As a result, wildflower season was shorter and arrived earlier. But Flickr photos showed that visits by people to Mount Rainier in 2015 peaked later than the flowers, after the height of wildflower season.

“We know from park surveys that the wildflowers are a major reason people visit Mt. Rainier National Park,” said lead author , a researcher at Rocky Mountain Biological Laboratory and Harvard University who conducted this study as a 91̽��doctoral student in biology. “They’re an iconic resource, drawing people from around the world.”

The team, led by 91̽��biology professor and senior author , downloaded and analyzed more than 17,000 photos on Flickr taken in the subalpine region of Mount Rainier National Park from 2009 to 2015. The team used publicly accessible images that contained embedded GPS data, which allowed the team to know where in the park the photos were taken. They scored the images for the presence or absence of blooms from 10 species of wildflowers common to the subalpine meadows.

“These are a very nontraditional source of data, but they proved to be very informative,” said Hille Ris Lambers. “It allowed us to see when the flowers were blooming at a lot of different locations around the park.”

The team combined the data on wildflower blooms from the photos with snowmelt data — taken from 190 sensors placed across Mount Rainier — as well as park visitor data to model the wildflower seasons and peak visitor times from 2009 to 2015. They discovered that the earlier the snowmelt, the higher the “mismatch” between peak wildflower season and peak visitor times.

According to their model, for every 10 days of earlier snowmelt compared to today’s average, peak bloom in the subalpine meadows comes 7.1 days earlier and the total bloom season shortened by 0.36 days. People come earlier, too: Peak visits occurred about 5.5 days earlier. But that doesn’t keep pace with the flowers. In 2015, when snow melt was about two months earlier, the researchers discovered a 35% decrease in match between peak wildflower season and peak visits to the park compared to a late-melt year like 2011.

The study is among the first to examine the relationships in timing between people and a changing ecosystem, which raises questions for management of parks and preserves — and how to communicate with the public. The team only measured “mismatch” between wildflowers and visitors after the fact. With additional research, scientists may be able to predict outlying years early, alerting the public to visit sooner than normal to view the meadows.

This isn’t just about missed connections between wildflowers and people. Conditions in 2015 were an outlier by today’s standards; by the end of this century, scientist predict that 2015-style early snowmelts could be a regular occurrence. Beyond changes in peak bloom times, Hille Ris Lambers’ group has shown that in 2015 species bloomed in a different order, creating “reassembled” communities with unknown consequences. The meadows also are facing other stressors as the climate warms.

“These subalpine ecosystems are in real trouble,” said Breckheimer. “For example, climate change is allowing trees to encroach into the meadows at Mount Rainier and other sites across the West, and the meadows are not moving uphill as fast as the trees.”

It’s critical to retain public support for these precious natural resources, Breckheimer added.

“There’s a real question whether — or how much — we should intervene to protect meadows, by clearing trees through active management, for example, as we keep pushing ecosystems with climate change, and those systems keep getting further out of equilibrium,” said Breckheimer. “If visitor peak and flower peaks are at different times, it might affect public support for some of these measures for how public lands are managed in the face of climate change.”

Co-authors are , a 91̽��instructor in biology who conducted this research as a 91̽��doctoral student; , a 91̽��research scientist in the Department of Civil & Environmental Engineering and the eScience Institute; Anna Wilson with the Free Science Project; , a 91̽��professor of civil and environmental engineering; and Regina Rochefort with the National Park Service.

For more information, contact Breckheimer at ian_breckheimer@fas.harvard.edu and Hille Ris Lambers at jhrl@uw.edu.

Central to the field of ecology is the mantra that species do not exist in isolation: They assemble in communities — and within these communities, species interact. Predators hunt prey. Parasites exploit hosts. Pollinators find flowers.

Yet these interactions are built on more than just serendipity, because species adapt over generations to environmental cues. But when conditions shift due to climate change, species might change markedly in response — creating “reassembled” communities that might show disrupted interactions among species.

Recently, a trio of ecologists from the 91̽�� witnessed such reassembly. It was by accident: They were collecting data on the subalpine wildflowers that bloom each summer on the slopes of , a volcano stretching 14,411 feet high (4,392 meters) in the Cascade Range of Washington state. As they report in published online on Oct. 11 in the journal , an unseasonably warm, dry summer in 2015 caused reassembly among these subalpine wildflower communities.

The conditions in 2015 gave the team — consisting of doctoral student , doctoral student and biology professor — a preview of what subalpine communities may look like by the end of this century. By then, significant climate change is expected to permanently alter environmental cues that wildflowers rely upon and make community reassembly a more common phenomenon — with unknown consequences for species interactions in those communities.

“2015 was such an outlier that it gave us a glimpse of what this environment on Mount Rainier might be like toward the end of this century,” said Theobald, who is co-lead-author on the paper with Breckheimer. “Conditions were so warm that they affected the flowering time and flowering duration of species, forming communities in 2015 that simply did not exist in the other years of our study.”

Their study is one of few to demonstrate evidence for community-level reassembly among multiple species.

“These reassembled communities could potentially change the interactions among wildflowers and other species in this subalpine setting,” said Theobald.

For six summers from 2010 to 2015, Theobald tracked environmental conditions and plant behavior for 48 species at 70 field plots, each one square meter, along the southern slope of Mount Rainier. The plots ranged from 1,490 to 1,901 meters in elevation. Within each plot, Theobald used sensors to record temperature, snowmelt and soil moisture content.

“At these elevations on Mount Rainier, snow is the major driver of plant behavior, because the annual cycle of flowering and reproducing cannot begin until the snow melts,” said Hille Ris Lambers. “If there is snow on the ground, plants cannot photosynthesize, and if they cannot photosynthesize, they cannot grow.”

When the sensors reported that snow had melted at each plot, Theobald collected data on when plants would emerge, flower and begin to produce fruit. These included species familiar to hikers such as avalanche lily, magenta paintbrush, mountain blueberry, wild huckleberry and wild lupines.

Most of these plants are perennials, which retreat underground each winter. But when snow melts, they typically have a two- to four-month window — depending on elevation and position — to grow, flower and produce fruit and seeds for the next generation before snow returns.

In 2015, conditions were so warm that, on average, snow began to melt at the study plots 58 days earlier than in 2010-2014. The team recorded major shifts in the bloom times of wildflower species. All of the species — 100 percent — flowered earlier in 2015 and 54 percent of species also lengthened their flower duration that year, some by as many as 15 days. The remaining species showed shorter flower duration, in one case by nearly 19 days, possibly due to accelerated soil drying, altered pollinator activity or other factors.

Since species shifted in different ways, conditions in 2015 produced new patterns of reassembled wildflower communities, with unknown ecological consequences.

“These are species that have always coexisted at these subalpine sites,” said Theobald. “But in 2015, we saw species flowering at the same time that normally flowered weeks apart.”

The team saw the most dramatic signs of reassembly among plants that normally flowered early in the summer. These plants tended to grow at sites experiencing less snowfall — such as plots at lower elevations, or along ridges and slopes instead of coves and valleys, where snow tends to accumulate. In addition, the plants that tended to lengthen flowering duration did so if they experienced a greater number warm, photosynthetically “productive” days in 2015.

Reassembly on the scale that the researchers saw in 2015 — and that Mount Rainier may see every year by the end of this century — may change interactions among species. For example, plants could compete for access to pollinators, which at Mount Rainier include bumblebees, flies and hummingbirds.

“We simply don’t yet have enough information to know who the ‘winners’ and ‘losers’ of reassembly will be, or even what ‘winning’ or ‘losing’ in such a scenario would look like,” said Theobald.

To predict that, scientists must observe and test how ecological reassembly affects reproduction for all species in these regions — from flowers and pollinators, to even the bears that feed on subalpine berries. These effects will also impact the people who visit these sites and try to preserve them.

“All of these interactions among species — and how those interactions will shift due to climate change — will affect how we manage these sites,” said Hille Ris Lambers. “After all, Mount Rainier is a national park that is here for all of us, as well as the species that call it home.”

The research was funded by the National Science Foundation, NASA, the 91̽��, the Mazamas and the Alpine Club. Theobald is now a postdoctoral researcher with the UW’s .

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For more information, contact Theobald at ellij@uw.edu and Hille Ris Lambers at jhrl@uw.edu or (206) 543-7389.

DOI: 10.1002/ecy.1996

Grant numbers: DEB-1054012, DGE-1256082, NNX-14AC34G.

In the face of adverse conditions, people might feel tempted by two radically different options — hunker down and wait for conditions to improve, or press on and hope for the best. It would seem that trees employ similar options when the climate turns dry and hot.

Two 91̽�� researchers have uncovered details of the radically divergent strategies that two common tree species employ to cope with drought in southwestern Colorado. As they report in in the journal , one tree species shuts down production and conserves water, while the other alters its physiology to continue growing and using water. As the entire western United States becomes warmer and drier through man-made climate change, these findings shed light on how woody plants may confront twin scourges of less water and hot weather.

The authors, 91̽��biology graduate student and biology professor , wanted to understand if different tree species employ similar coping strategies for drought, and how these strategies would affect their future ranges in a warmer and drier climate. They compared how two common tree species differ in terms of shape, growth rate and physiology across wet and dry portions of their native ranges.

“We really wanted to identify the entire suite of strategies that a plant can use to grow in drier environments, as well as which of these strategies each tree would employ,” said Hille Ris Lambers.

Along the slopes of the La Plata Mountains in Colorado’s , dry and hot conditions at lower elevations limit tree growth and survival. The (Pinus ponderosa) grows along these lower elevations. Higher up the slopes, (Populus tremuloides) dominate, and the lowest point of the aspen’s range overlaps with the higher reaches of the ponderosa pine. In the summer of 2014, Anderegg and a team of 91̽��undergraduates collected leaf, branch and tree ring samples of both trees at the extremes of these ranges to learn how they adapted to drought conditions, measuring qualities like growth rate and water tension within the woody tissue.

Anderegg discovered that the trembling aspen and ponderosa pine adopt opposite strategies to cope with drought, with implications for their range and survival.

“On average, this region has already warmed up over 1.5 degrees Fahrenheit in the last 30 years,” said Anderegg. “And what were once 100-year droughts are expected to become more frequent in the coming centuries.”

The ponderosa pine used a strategy of “drought avoidance” by conserving water, especially by shutting the tiny openings on its leaves to prevent water loss and slowing growth. The trembling aspen, in contrast, deployed strategies that would allow it to keep growing — at least for a while — during drought, with no change to water conservation strategies.

“On the dry end of their range, the trembling aspens are relatively short with these really fat leaves,” said Anderegg. “Internally, they also grow really strong xylem vessels, which move water inside of the tree. As a consequence, they are much denser and they also grow slower.”

These strategies may influence the contraction of each tree species’ range over time. The trembling aspen’s push to grow might make it more vulnerable to severe or prolonged drought, especially at its dry lower range. Anderegg believes the aspen’s range might shrink in “fits and starts” as a hotter a drier climate settles in. A severe drought in 2002, he notes, already killed off large numbers of trembling aspen at the study site.

The ponderosa pine’s strategy of “drought avoidance” might mean that its range will contract more gradually than the trembling aspen’s, the authors note. These differences in adaptation will reshape forest ecosystems in the face of climate change, they believe. Anderegg and Hille Ris Lambers would like to identify the tree life stages most vulnerable to drought, which might affect how quickly their ranges contract, and what forest policymakers could do to try to cope with these changes.

“If we know how the forests will change, we can hopefully manage things so that we don’t lose the things we love and rely on — things like air and water purification, erosion control and forest biodiversity,” said Anderegg. “We’d like to be able to mitigate some of the negative effects to this vast public resource and keep climate change from being hugely detrimental.”

Their research was funded by the 91̽��Biology Edwards Grant, the Charles Redd Center for Western Studies, Sigma Xi, the American Alpine Club and the National Science Foundation.

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For more information, contact Anderegg at 541-790-1096 or ldla@uw.edu and Hille Ris Lambers at 206-543-7389 or jhrl@uw.edu.

Grant numbers: DGE-1256082 (NSF).