Jesse A. Logan ’77 PhD is hiking up a mountainside in Yellowstone National Park and walking back in time. He starts at 8,600 feet above sea level, in a forest thick with the scent of fir and lodgepole pine, and with almost every spry step, the scenery changes. There’s an understory of grouse whortleberry, then accents of mountain bluebells and higher still, the whitebark pine, one of the oldest organisms of the Interior West.
Finally, the vegetation gives way to large swatches of scree. Logan’s 70-year-old legs have gone up 2,000 feet and back more than 10,000 years, from the lush vegetation of the twenty-first century to the hardscrabble world of the Pleistocene Epoch, when glaciers scraped the earth and plants struggled to hang on.
The view east and north opens up, and Logan can peer into the Shoshone National Forest’s Crow Creek drainage. It’s a long trough fringed with peaks and mesas and vast groves of dead trees. One section of trees was burned in the spectacular fires of 1988. But even larger sections are forests of whitebark pine ravaged by the mountain pine beetle.
As a U.S. Forest Service entomologist in the 1990s, Logan developed a model that showed global warming could raise temperatures enough for the beetles to flourish and overwhelm the pine. His prediction came true beginning in 2003, when a beetle outbreak swept over much of the Greater Yellowstone Ecosystem. The trees turned a glowing red as their needles died, then became “ghost forests” of bleached skeletons.
“I’ve watched all of this happen,” says Logan. “First the south-facing slopes went, naturally, then the north-facing slopes. It’s just heartbreaking.”
The view is a peek into a future of increasing global temperatures and rapidly changing natural relationships. For thousands of years, plants, animals, bacteria, and fungi have secured a tenuous foothold on the planet by adapting to specific niches and relationships. Now, a seemingly subtle rise in the average global temperature—1.5 degrees Fahrenheit since 1880, according to the Intergovernmental Panel on Climate Change—is prompting a cascade of ecological changes. They could only hasten as temperatures rise as much as 8 degrees more by the end of this century.
Earlier this year, the Third National Climate Assessment, an analysis by more than 300 experts, cited 30 observed and projected biological responses to climate change in the United States. Among them: the loss of habitat for nearly a dozen marine mammals, earlier salmon migrations that risk being out of synch with optimal spawning conditions, fewer trout in the West, earlier bird migrations, and dying western conifers. In general, the assessment’s Climate Change Impacts in the United States says climate change can reduce the ability of ecosystems to improve water quality and regulate water flows. It can also overwhelm the ability of ecosystems to buffer extreme events like fire and floods. Some species may decline and even become extinct, “altering some regions so much that their mix of plant and animal life will become almost unrecognizable.”
One need only look at the salamanders Rod Sayler traps at the edge of the Pullman campus. The creatures live and breed in small pools around the arboretum, metamorphosing from larvae to adults as the pools dry. But if the pools dry too quickly, the salamanders emerge smaller and less fit to make their way in the world.
“Salamanders are kind of a canary in the mine, as so many species are,” says Sayler, who teaches conservation biology as an associate professor in Washington State University’s School of the Environment. “They show us that we have these changes going on in the environment… This is just one tiny example of all these other multitudes of changes going on at the same time that are affecting our ecological communities.”
Exactly how those communities will be affected, though, is subject to a lot of fine, as-yet-unwritten print. In a way, climate change is scrambling the natural world so much that it is sending ecologists back to the drawing board.
“I always say that one of the products of climate change is uncertainty,” says Ken Raffa ’80 PhD and professor of forest entomology at the University of Wisconsin–Madison. “We can say with certainty some products of climate change are rising ocean levels or changing insect ranges. But I think we have to be honest and say another product of climate change is more often we find ourselves answering intelligent questions by saying, ‘I don’t know’ about things we used to know a lot about.”
“The more we learn, the more complicated it starts to look to us,” says Jesse Brunner, an assistant professor in the WSU School of Biological Sciences studying the effect of climate change on the blacklegged tick, carrier of several diseases, including Lyme disease.
“I remember when I was first hearing about climate change and disease, it was really simple relationships,” Brunner says. “It was things like, warmer temperature, faster development, everything goes to hell. But the reality seems to be, the climate gets warmer and more variable and precipitation changes and certain types of organisms might do a little bit better, at least in certain stages of their life cycle. But others might do worse. Trying to figure out the net outcome of that is a messy business.”
In a way, the term “global warming” confuses the issue. Just as some places might actually get colder, the effects of rising average temperatures will often be quite localized. To see this, we’ve arranged with several WSU faculty and alumni to take a virtual tour of the country, from a New Hampshire hillside to the tidal flats of San Francisco Bay, with stops in between. Along the way, we’ll see researchers observing and anticipating the effects of rising temperature on the natural world, a bewildering process that takes ecology’s already complicated study of connections and activates a whole new set of circumstances.
Some are good, some are bad. Whatever the outcome, ecologists tend to agree that the warmer future will be profoundly different.
“This is a new game, no question,” says Logan, who expects negative impacts to outweigh potential benefits. “It’s really an interesting time to be an ecologist, but not a particularly happy time.”
Hubbard Brook Experimental Forest, North Woodstock, New Hampshire
In the fall of 2009, Michael Webster left a faculty appointment at WSU to take an endowed chair in ornithology at Cornell University. He moved, as the crow flies, 2,000 miles from Pullman to Ithaca, New York. The trip was as easy and risk free as for just about any other animal. And quite possibly easier than the move a black-throated warbler might make as global warming shifts its habitat up or down a hillside.
“We’re very flexible animals,” says Webster, who still collaborates with WSU faculty. “We have technology that helps us deal with a huge range of conditions. These birds don’t necessarily have that technology and it’s unclear how flexible they are and how well they can adapt to a changing climate. And that’s what we’re trying to figure out.”
The black-throated blue warbler is a forest bird that migrates from the Caribbean to breed each summer in the northeastern United States and southeastern Canada. For years, Webster has studied the bird in the Hubbard Brook Experimental Forest, one of more than two dozen long-term ecological study sites run by the National Science Foundation and other federal agencies.
Like most creatures, the bird has evolved to breed in a specific niche. If average temperatures change and alter that niche, the bird could find itself in a bind, as would other birds, insects, and other animals.
“Basically there are three options for those species,” sa
ys Webster. “One is to adapt to the changing conditions. Another is to move to where conditions are more favorable for you. And the third is to go extinct, at least locally.” The creatures that go extinct are, in effect, fatally bound by their evolution. Unlike a human, they can’t pack a moving truck and go to a new clime.
“They become trapped by their own ecology,” says Webster.
As it happens, more is known about the Hubbard warblers than just about any other breeding population. With climate conditions changing, Webster and his colleagues saw a chance to ask, “Is this good or bad for the birds?”
Webster simulated a warming climate with more food, putting out meal worms and training the birds to eat them. He found that, to the extent a warming climate increases the abundance of food, the birds might fare better.
“They do modify what they are doing in a way that is at least partially adaptive for the changing conditions,” he says. “They do OK and in fact, to a certain level, they do well. This is one of the birds that at least in the short term might benefit from changing conditions.”
Indeed, if they have more food in the spring, they could breed as soon as they return from migration, and might make two broods. But a long-term warming trend could also affect the structure of the forest, shading out the understory so there is less food for insects. This is probably what’s happening at lower elevations.
“So over the longer term, it may be not good for the birds,” Webster says. “There’s this complicated thing where, short term, it’s probably good for them. Long term, possibly not.”
Researchers have noticed that birds in Europe, where ecological conditions are more similar, are having young out of sync with the emergence of caterpillars, a major food source. In the United States, where forests are more varied, there are more varieties of caterpillars and a less predictible peak in food abundance.
Still, what’s good for the warbler may not be good for the wren, and ecologists struggle to find an overarching theory for the effect of a rapidly changing climate.
“So far, I don’t see a general rule of thumb emerging,” says Webster. “It looks like it might be much more species by species.”
San Francisco Bay
Back in the mid-’70s, while finishing his WSU doctorate in zoology, James Cloern saw an episode of NOVA featuring U.S. Geological Survey scientists studying the inner workings of San Francisco Bay’s physics, chemistry, and biology.
“Wow,” he recalls thinking. “Wouldn’t that be a neat place to work?”
Six months later, he was in San Francisco as a USGS ecological modeler. That was 38 years ago. At the time, the USGS San Francisco Bay program was already looking at climate variability—cyclical changes in precipitation, river flow, wet years, and dry years. In the last 20 years, the changes have been more continuous. Their footprint has also been huge.
“In our long-term studies, we’ve detected large changes inside San Francisco Bay that we think are attributed to climate-driven changes that are operating across the entire North Pacific Ocean,” he says. “In terms of everything being connected, in order to understand a place like Puget Sound or Willapa Bay or San Francisco Bay, we need to understand what’s going on in the local watershed, in the far watershed and across the North Pacific Ocean basin.”
In 2011, he was the lead author of a study in the online journal PLOS ONE projecting changes to the bay under two contrasting climate scenarios of fast and moderate warming. Aimed in part at helping resource managers plan for a warmer future, both scenarios anticipated a shrinking water supply, wetter winters and drier summers, rising sea levels, “reduced habitat quality for native aquatic species, and expanding envelopes of environmental variability into regimes we have not experienced.” Salt water will intrude more into freshwater areas, hurting irrigation and supplies of drinking water. Four runs of native Chinook salmon will spawn in summer waters warmed to “lethal levels” for their eggs.
“Sea level rise in a sense is a straightforward problem,” says Cloern, “whereas sustaining endangered, indigenous species is really challenging because it’s not the response of just one thing. It’s not just increasing water temperature. It’s not just changes in salinity. It’s changes in the food supply. It’s changes in habitats that are required for spawning and for avoiding predators. It’s changes in competition from invasive species that are going to find themselves in a habitat that’s more favorable to them. So it’s a multidimensional, complex, much more challenging problem.”
Lyme, Connecticut, and Points West and North
When we think of ecology—the study of organisms and how they interact with each other and their environment—it’s easy to forget that humans are one of those organisms. The blacklegged tick does a good job of driving that point home.
The tick transmits the bacterium Borrelia burgdorferi, the cause of Lyme disease, so named after it was seen in three communities centered around Lyme in 1975. At the time, outbreaks of the disease were confined to coastal southern New England. It has since spread through the Northeast and upper Midwest and become the most commonly reported vector-borne disease in the United States, according to the Centers for Disease Control.
Now comes the era of climate change, creating what Jesse Brunner, a disease ecologist and assistant professor in the School of Biological Sciences, calls “an interesting, natural experiment that’s happening right in front of us.”
Here’s a simplified form of one scenario. If temperatures go up, more ticks will survive, breed, and infect. Early on, it was widely thought the ticks required mild winters to survive, like those found near coastal areas, and that they were restricted from moving inland by cold, dry winters.
But the invasion of recent years negates that hypothesis, says Brunner. The ticks exist in lots of places without mild winters. Thinking that rare cold snaps might still kill the ticks off, Brunner one winter put some in the ground in mesh bags, digging them up every few weeks to see which survived. They seemed to be unaffected by the cold, finding places just warm enough in the ground to survive.
Still, Canadian researchers hypothesize the ticks might run through their life cycle faster with warmer temperatures. Going from eggs to larvae to nymphs to adults generally takes two or three years. The longer that takes, the more risks they face, says Brunner, leading to fewer progeny.
So the cold overwintering hypothesis gives way to the warmer, faster development, less risk hypothesis. As Brunner puts it, this can make more places “permissive” for ticks.
“The regions in North America that are permissive for ticks are probably expanding,” he says. “At least on the northern edge it seems to be expanding, just because it’s getting warmer in the northern regions and they’re able to complete their life cycle quickly in the northern region. Those areas that could not have ticks before probably now can have ticks.”
But a tick’s survival also depends on its ability to get a blood meal, which it does by “questing.” This involves climbing high up a piece of vegetation and sitting with arms extended to grab a passing creature—a deer, a mouse, opossum, a human. But elevated, open questing spots can be dry, and all that time above the humid leaf litter with arms extended dries a tick out. Meanwhile, with global warming, the Northeast summers are forecast to be hotter, with less frequent, larger rains between long dry spells.
“My suspicion is that there’s going to b
e a lot more time that’s basically bad for questing,” says Brunner. “They’re going to have a harder time finding a host. So all of a sudden, developmental times may not be the issue. The ability to complete your life cycle, that may be easier to do under future climate. But getting a host might be a lot more difficult.”
No blood meal, no tick.
Then there’s the effect that climate change has on the host themselves. Their populations may be sensitive to temperature, as well as their food sources. And remember the tick’s pathogen, the bacterium Borrelia burgdorferi. Its ability to replicate is also affected by temperature.
“It could be that under warmer conditions, pathogens might replicate faster,” says Brunner, “which means they might be more likely to get transmitted to a new host. In a lot of hosts, though, the immune system can be temperature-dependent as well. For a lot of arthropods, their immune system functions better at warmer temperatures.”
At least for now, he said, “We don’t know which one is going to end up winning the temperature race.”
The Greater Yellowstone Ecosystem
For thousands of years, the whitebark pine has flourished by going where no tree dares to go—the bitterly cold, windswept reaches high up on the western spine of the continent. It has colonized poor soils, enabling an ecosystem in which calving elk have cover and Clark’s nutcrackers, squirrels, and bears can thrive on the tree’s fat- and protein-laden nuts. As a friend of Logan’s puts it, the trees “turn granite into grizzly bears.”
But the tree also has the distinction of being, as Logan puts it, “one hell of a survivor, not a particularly good competitor.” This has been borne out by the mountain pine beetle’s ability to so utterly overwhelm the tree in what Logan has called a “perfect storm” of circumstances.
First, winters grew milder, letting more adult beetles survive. Some adults could overwinter and attack early in the year, while other adults attacked later.
Then there’s the chemistry. Typically, the beetle has attacked lodgepole pine, which tends to grow at lower elevations than the whitebark. The lodgepole has a potent arsenal of resins to repel or kill adults and prevent eggs from hatching. The whitebark has some of the same chemicals, called monoterpenes, but not as many. Moreover, attacking female bark beetles can convert some of the tree’s chemicals into pheromones used to attract males, rallying the troops.
“They use the tree’s defense chemicals as precursors to the aggregation pheromone,” says Raffa, the Wisconsin entomologist, who last year wrote about the whitebark chemistry in PLOS ONE. “So as long as the tree is fighting back, it’s bringing in more and more beetles. It’s kind of a multi-million-year-old version of jujitsu.”
After burrowing through the tree’s bark, the beetles make a J shape in the phloem, the bark layer that takes nutrients from the leaves to the roots. A year after an attack, the tree’s needles turn red and eventually fall, leaving a ghost forest.
“Pretty soon, you just see bare skeletons,” says Logan.
In 2009, Logan did an aerial survey of the Yellowstone ecosystem and found 95 percent of the whitebark pines had some level of mortality, with nearly half losing their ecosystem services like food for grizzlies and retained snowpack. Logan sees the damage most everywhere now, especially since much of his retirement—some 100 days a year—is spent back-country skiing in the park.
For scores of other species, the effect of global warming can be unclear, complicated, and subject to all manner of ifs. But as Logan said upon accepting a forest entomology award in 2010, the beetle outbreaks on the whitebark pine “are perhaps the clearest example to date of a predicted ecological response to global warming that was borne out by subsequent events.”
He may well be the nation’s biggest advocate of the whitebark pine, telling its story to the likes of High Country News and The New York Times. Encountering a group of hikers on the way to Avalanche Peak, he says, “You guys notice all the trees? Bark beetle.” When a visitor suggested that the whitebark is not a particularly good looking tree, he politely said those could be construed as fighting words.
But he sees no quick fix. Pesticides are impractical. Replanting trees is prohibitively expensive and, like pesticides, outside the park’s guiding principle of letting nature take its course.
So Logan takes the long view. Driving above the treeline one afternoon, he stops at the Rock Creek Vista Point. At 9,190 feet above sea level, it must be one of the highest rest areas in America, with fortress-like privies and expansive views of rock and stunted, twisted krummholz versions of whitebark pine.
“I just don’t see much optimism in the current distribution of whitebark in this system,” said Logan. “The way climate is going, I see massive disruption for grizzlies, for water retention. We’re in for some serious times.”
He recalls how his grandfather, who was born in 1856, told of seeing a fungus wipe out the American chestnut, an enormously valuable tree in the woodlands of the eastern United States. Logan expects that he too will explain to his own grandchildren how a major tree left the landscape.
But taking an even longer view, he says the whitebark’s future may well be here among the krummholz. High enough to avoid the reach of the beetles, the trees can serve as a genetic repository, if and when the climate stabilizes or the tree develops some sort of adaptive response to the beetle. Meanwhile, it can hunker down in a forbidding redoubt of rock and snow, growing at a glacial pace, taking half a century to so much as put out its first pine cone, awaiting the day its time returns.
Infographic: The Scrambled Natural World of Global Warming – a sampling of WSU research projects in North America (PDF)