A Jeffrey pine tree growing in far eastern Tulare County is the highest in altitude tree ever recorded in California. The new altitude record, however, has a dark cause: species creep due to a rapidly shifting climate in the Sierra Nevada.
Chance Discovery During a Pleasure Hike
Back in September of last year, Hugh Safford made the snap decision to take a side hike up the south face of Mount Kaweah, a 13,807 foot peak in Tulare County’s portion of Sequoia National Park. He and his wife were trekking a portion of the High Sierra Trail, which runs north-south through the heart of the Sierra Nevada, and were camped at the mountain’s foot. He planned to make a morning of it to take in the view from atop Mount Kaweah.
At 11,800 feet up the mountain’s south side where he stopped for a drink of water and a look at the spectacular vista, his plans changed. He’d found something he knew had no business being there: a stunted Jeffrey pine clinging to life.
“And this is where you pop out of what you’d call continuous forest at that point,” Safford said.
In other words, a tree normally found much farther downhill at 9000 feet of elevation was living above the timberline.
It wasn’t alone. With the Jeffrey pine were species normally found skirting atop the forest’s edge at 11,800, like lodgepole and foxtail pine trees that are adapted to that elevation.
Safford instantly knew what he was seeing was “a strange critter” and very much out of place. That’s because he’s more than a casual hiker. Safford is also a forest ecologist who works as a faculty researcher at UC Davis’ Department of Environmental Science and Policy. Head of the Safford Lab at UCD, his research normally focuses on forest vegetation and fire ecology.
“And being an ecologist who works a lot in high elevation forests, I know what a Jeffrey pine looks like,” he said. “I work with it a lot and I know it doesn’t belong at 11,800 feet.”
Between the Timberline and the Treeline
While the timberline is where the forest thins out to a few scattered trees, the treeline is where they stop growing altogether. When Safford reached the treeline at just under 13,000 feet, he got another surprise. But it wasn’t why he was there at all.
“This was not a science expedition,” he said.
Instead, it was the area’s fabled beauty that drew him here. He and his wife were checking an item off their shared bucket list.
“My wife and I like to do long distance hiking, and we had seven or eight days and decided we were going to do the High Sierra Trail, because I’ve seen the beginning of it and the end of it,” Safford said. “And everyone who’s walked it has told me it is one of the best trails in the world.”
On their fourth day out, Safford got restless. They were hiking the trail backwards, starting from Mount Whitney. By the fourth day they’d reached the base of Mount Kaweah.
“And I hadn’t climbed Mount Kaweah, and I’m a little bit hyperactive when it comes to wanting to climb mountains when I’m sitting at their base,” Safford said. “And so one morning I took off at 6 a.m.”
At first the spontaneous hike went as Safford expected.
“I started marching up this thing and I’m walking through — or sort of slogging steeply through — a forest of foxtail pine and lodgepole pine, which is what you’d expect at that elevation,” he said. “And then I pop out there at 11,800 (feet) to get a drink and look out over the amazing scene that you get once you get out of the forest there. And there was a Jeffrey pine. And I was gobsmacked.”
The Highest Tree of All, but How Did It Get There?
Safford knew he was seeing something very much out of the ordinary. So, after making this more significant discovery, the scientist moved from vacation mode into research mode. He began surveying for more Jeffrey pines and was immediately rewarded.
“I mean, the nearest one I’d seen was probably two and a half, three miles away and certainly 2,000 feet lower, an adult tree,” Safford said. “And so my climb up the mountain turned into a science expedition, basically, because I saw another dozen of them right there. And I started thinking, well, if I’m going to climb this mountain, I’m going to see how far this Jeffrey pine goes, because I already can’t believe what I’m seeing.”
The mountain wasn’t done with shocking Safford. When he reached the area near the treeline, he found a Jeffrey pine growing at 12,657 feet. It would turn out to be the highest altitude recorded for a living tree in California. Safford’s paper describing his discovery appeared in the January-March 2025 issue of Madroño, the scientific journal of the California Botanical Society.
Yet a mystery remains. How did these trees get so high up Mount Kaweah? Safford immediately suspected he knew what mechanism was at work. The Jeffrey pine seeds flew there.
.”Given that the nearest Jeffrey pine was as far away as I’d seen, and given that I know that Jeffrey pine doesn’t grow at this elevation, it had to be dispersed long distance, and that basically lands at the foot of a bird of some kind,” Safford said.
Crow Relative Did the Heavy (Air) Lifting
Safford and the experts he’s spoken with have a suspect species in mind, the Clark’s nutcracker.
“It’s a bird that really moves,” Safford said. “And that’s got to be the culprit.”
The Clark’s nutcracker is a close relative of common birds like crows, ravens and scrub jays. Collectively, this bird family is known as the corvids. It could have been another similar species, but Safford is confident that it’s their prime suspect behind the pine’s climb. Still, they’re going to do more research to be certain.
“We will spend some time doing this a little more scientifically to be sure that it’s not a type of jay or something else moving it,” he said. “But it’s got to be Clark’s nutcracker based on everything we saw and all the people that we’ve talked to. And we saw plenty of Clark’s nutcrackers flying around in the forest up there.”
The Clark’s nutcracker is thrifty. It gathers thousands of seeds in a throat pouch, carrying them from lower elevations to above the timberline. There, it coughs up the seeds and stores them for the start of the warm season at winter’s tail end.
“It’s a very smart bird. And a single bird, it seems impossible, but a single bird like that can cache anywhere from 10 to 30 thousand seeds, during the period of seed maturation,” Safford said. “And they just scattered them all over the landscape so they can go find that food when they need it in the winter and the early spring.”
But the bird doesn’t just stash the seeds randomly. Putting them above the timberline where the weather is coldest preserves the food value. And the best place for them is in the frozen ground.
“They use their bill, they shove their bill down into the ground and so it (the seed) gets a little bit of soil above it,” Safford said. “And in terms of the typical caching location and elevations like this, I’ve been told by those people who know these sorts of things that it’s really common for them to particularly hit south slopes where you have a little bit of soil, and it’s often done in sort of rocky enclosures.”
Southern slopes also catch the most sunshine as the seasons change. That too, Safford thinks, influences where the birds hide the seeds.
“Exactly why that relates to where Clark’s nutcracker would cache, I think it’s probably because south-facing slopes are going to be protected from too much snow and probably is going to be one of the first places on a high mountain to open up in the late winter and early spring,” he said.
Why Here and Why Now? It’s Climate Change
That the trees are growing where they’ve never been seen before is a sign something much greater is going on than birds hiding their caches. It’s a definite sign the climate of the Sierra Nevada is altering, and it’s altering quickly.
The Clark’s nutcracker has likely been using this technique to survive until spring arrives for an extremely long time. Yet it’s only now in the 21st century the Jeffrey pine is suddenly growing outside its historically established range.
“(The Jeffrey pine seeds have) probably been getting deposited there by Clark’s nutcracker for millennia,” Safford said. “At this point, it’s starting to get warm enough that some of those seeds put in cold storage are actually able to germinate and survive through enough years to become a small tree.”
None of the Jeffrey pines Safford found at the highest elevations were older than 25 years, and none of them were mature to the point of sprouting cones. These trees are newcomers. But their migration to even higher elevation may not be over yet.
According to California’s Fourth Climate Assessment – Sierra Nevada Region Report from 2018, there will no longer be any snowpacks below 6,000 feet in the Sierra by the end of this century. Temperatures in the Sierra will climb 6 to 9 degrees Fahrenheit, moving the snowline up as much as 3,000 feet higher. This means the snowpack will be reduced by as much as 60% across the entire Sierra Nevada.
And meanwhile droughts and extreme winter storms will become more frequent and intense, and not just in the mountains. The valley floor can expect increased flooding and drier droughts. The entire watershed and its timing will be altered. How that will happen cannot be predicted accurately, the report states. It’s prediction of our region’s future is grim.
“The combination of warmer temperatures and greater precipitation variability are expected to increase food risks while also increasing the prevalence of droughts,” it states. “These changes in climate pose daunting challenges to the region’s landscapes, resources and communities.”
Those include increased fire risk and damage, disruption and loss of ecosystems and species diversity, unpredictable changes to the water system, and the disruption of Sierra communities that depend on the industry the area generates.
Safford, working at the time as regional ecologist for the USDA-Forest Service’s Region 5 (California, Hawaii, Pacific territories), was a lead co-author of the Sierra Nevada Region Report.
Not a Normal Case of Species Creep: ‘A Leap for Tree-Kind’
Despite the debate created by the comedy troupe Monty Python — Do you mean to suggest coconuts migrate?! — trees do, in fact, migrate. The slow process is sometimes referred to as “species creep,” but that’s not really what’s happening here, Safford said.
“I think in this case, actually, no,” he said. “What I want to make clear is that the idea of a species sort of creeping uphill is the general model that most people have in their minds when they think about the way that climate warming works.”
Soil conditions and the climate have the greatest direct effect on plant evolution and where individual species can live. As the climate warms, some species will extend their range while others will shrink. The Jeffrey pine is one of the lucky species that will have more room, at least for now.
“This is going to influence where forests are on high mountains,” Safford said. “As the climate warms there’ll be this slow uphill migration, and ‘migration’ is the proper word. It’s just that plants migrate at a very, very different scale than animals do.”
Other pines, like the foxtail and the lodgepole, are migrating the old-fashioned way. But a different mechanism is at work with the movement of the Jeffrey.
“Rather than just seeing foxtail and lodgepole pines slowly moving uphill, which is definitely happening as well, no question about it, you do see seedlings of them higher all the time, Jeffrey was flown over the top of them by a bird,” Safford said. “So it wasn’t a creep. It was big. It was a leap for tree-kind.”
Global climate change is the responsible factor. According to data published by the National Oceanic and Atmospheric Administration (NOAA), the Earth has warmed an average of 0.11 degrees Fahrenheit every 10 years since the 1850s. So far, the temps are up about an average of 2 degrees overall. But the rate of warming is increasing, with warming since 1982 happening three times as quickly than before. Every year, a new record high is set for global temperatures.
“At this point, it’s starting to get warm enough that some of those seeds put in cold storage are actually able to germinate and survive through enough years to become a small tree,” Safford said. “None of the trees I saw, and I measured I think it was 14 of them, and I saw another dozen at least, none of them had cones. even though some of them were at least 20 to 25 years old at the lower end down by where the dense forest was.”
An ongoing change in average temperatures isn’t the only factor at work. Dry conditions also let the Jeffrey pine survive in these new surroundings.
“Typically, we think of high elevation forests as being driven by winter cold. That’s the filter. If you can make it through that, you’re going to live,” Safford said. “But it’s so dry in the Sierra already. And now that it’s getting so much warmer, it’s that much drier. And so a species like Jeffrey pine is pretty uniquely adapted to that because it is much more drought tolerant than any of those other pines or species at that elevation.”
Many other species, however, will not be lucky enough to survive as their environments change.
Shrinking High-Altitude Sky Islands
The tops of high mountains are unique places. The conditions found there are extremes of cold and ice, as well as intense solar radiation, and often superlatively arid conditions. Because of this, these regions are sometimes known as “sky islands,” as the species living within them are finely tuned for surviving within them. They can live nowhere else.
“The worry that everyone has about climate warming in mountains is that mountains get smaller as you go uphill,” Safford said. “And as species are forced to move up to stay within sort of the envelope of their climatic tolerances, at some point they’re going to run out of space to be on anymore. And this is a big problem for species right at the top of mountains, particularly in lower mountains.”
If the climate changes enough, these ecologies and the species that inhabit them will disappear. That will be the end of these species in the wild, and perhaps everywhere.
“Once that climate pushes them off the top, you’re going to have to keep them alive in botanical gardens, or I don’t know where you’re going to keep them alive,” Safford said.
“And so it’s like sort of Gilligan’s Island,” Safford said. “These poor things are stranded up there. at the timberline in this inhospitable environment, and they’re not able to make cones yet, and the tops of most of the big ones are dead because when they stick out of the snow. I think they freeze and they get blasted by snow blast.”
Looking ahead, Safford sees vast changes coming to the High Sierra over the next few decades as the climate continues to warm unabated.
“That window is clearly moving uphill, because as I climb that mountain I found the highest seedling. It was almost 12,700 feet, which is just unbelievable. That’s higher than any recorded tree in any formal database in California for a Jeffrey pine. That makes absolutely no sense.
While the pines Safford discovered are struggling to survive — “So these trees are not enjoying their time there. It’s a harsh place to be,” he said — eventually he sees high-elevation forests of Jeffrey pines being likely. What will happen to less adapted species isn’t yet clear.
“But at some point, it’s going to get warm enough for those trees at the timberline to start growing cones,” he said. “And then I would predict that you’re going to see an explosion of Jeffrey pine all of a sudden because you’ll have seeds right there that are able to generate a bigger forest.”
But What About the Big Trees?
The giant Sequoia trees are not immune from the changes underway in the climate. Sequoias occupy very specialized environments, and they’ve already populated most of them. Yet their popularity has inspired botanists to start other groves around the world. But they only thrive right here.
And so their future, as so many other things in this era, is uncertain.
“They’re typically, not always, but often in north-facing pockets of relatively deep soil, sort of at those middle elevations,” Safford said. “There’s not a whole lot of that left in the southern Sierra that isn’t already occupied by them. So I think that in terms of moving uphill easily for a species that generates that kind of biomass, I mean, it needs access to some soil and some resources. Tough to say.”
Yet the largest living trees known to science are already dying because the climate is changing.
“Drought is killing them now,” Safford said. “There’s some insects that were not mortal agents before, but seem to be now. Obviously, we’re starting to kill giant Sequoias in fires, which is something that kind of blew my mind. So it’s something to be worried about.”
As for the migration of the Jeffrey pine, there’s still much to learn. Others may be growing even higher still, Safford said. He plans to return this summer to conduct a more thorough search. And he’ll be looking for local volunteers to join him.
To find out when and where to volunteer on the survey team, visit the Safford Lab at https://safford.ucdavis.edu/.