by Amy Stewart
A healthy tree can usually beat back invading beetles by deploying chemical defenses and flooding them out with sticky resin. But just as dehydration makes humans weaker, heat and drought impede a tree’s ability to fight back—less water means less resin. In some areas of the Rocky Mountain West, the mid-2000s was the driest, hottest stretch in 800 years. From 2000 to 2012 bark beetles killed enough trees to cover the entire state of Colorado. “Insects reflect their environment,” explains renowned entomologist Ken Raffa—they serve as a barometer of vast changes taking place in an ecosystem.
Typically, beetle swells subside when they either run out of trees or when long, cold winters freeze them off (though some larvae typically survive, since they produce antifreeze that can keep them safe down to 30 below). But in warm weather the bugs thrive. In 2008 a team of biologists at the University of Colorado observed pine beetles flying and attacking trees in June, a month earlier than previously recorded. With warmer springs, the beetle flight season had doubled, meaning they could mature and lay eggs—and then their babies could mature and lay eggs—all within one summer.
That’s not the only big change. Even as the mountain pine beetles run out of lodgepole pines to devour in the United States, in 2011 the insects made their first jump into a new species of tree, the jack pine, in Alberta. “Those trees don’t have evolved defenses,” Six says, “and they’re not fighting back.” The ability to invade a new species means the insects could begin a trek east across Canada’s boreal forest, then head south into the jack, red, and white pines of Minnesota and the Great Lakes region, and on to the woods of the East Coast. Similarly, last year, the reddish-black spruce beetle infested five times as many acres in Colorado as it did in 2009. And in the last decade, scientists spotted the southern pine beetle north of the Mason-Dixon Line for the first time on record, in New Jersey and later on Long Island. As investigative journalist Andrew Nikiforuk put it in his 2011 book on the outbreaks, we now belong to the “empire of the beetle.”
In a weird way, all of this is exciting news for Six: She is not only one of the world’s foremost experts in beetle-fungi symbiosis, but proud to be “one of the few people in Montana that thinks bark beetles are cute.” (She’s even brewed her own beer from beetle fungi.) As a child, she filled her bedroom in Upland, California, with jars of insects and her fungus collection. But as a teenager, she got into drugs, quit high school, and started living on the streets. Nine years later, she attended night school, where teachers urged her to become the first in her family to go to college. And when she finally did, she couldn’t get enough: classes in microbiology and integrated pest management led to a master’s degree in veterinary entomology, then a PhD in entomology and mycology and a postdoc in chemical ecology, focused on insect pheromones.
Six, 58, has light-green eyes ringed with saffron, and long silvery-blond hair streaming down shoulders toned from fly-fishing and bodybuilding. As several fellow researchers stress to me, she is the rare scientist who’s also a powerful communicator. “I think about what it means to be a tree,” she told a rapt audience at a TEDx talk about global forest die-offs. “Trees can’t walk. Trees can’t run. Trees can’t hide,” she continued, her sonorous voice pausing carefully for emphasis. “And that means, when an enemy like the mountain pine beetle shows up, they have no choice but to stand their ground.”
To a tree hugger, that might seem a grim prognosis: Since trees can’t escape, they’ll all eventually be devoured by insects, until we have no forests left. Especially since, with our current climate projections, we might be headed toward a world in which beetle blooms do not subside easily and instead continue to spread through new terrain.
But Six has a different way of looking at the trees’ plight: as a battle for survival, with the army of beetles as a helper. She found compelling evidence of this after stumbling across the work of Forest Service researcher Constance Millar, with whom she had crossed paths at beetle conferences.
Millar was comparing tree-core measurements of limber pines, a slight species found in the Eastern Sierras of California that can live to be 1,000 years old. After mountain pine beetles ravaged one of her study sites in the late 1980s, certain trees survived. They were all around the same size and age as the surrounding trees that the beetles tore through, so Millar looked closer at tree-ring records and began to suspect that, though they looked identical on the outside, the stand in fact had contained two genetically distinct groups of trees. One group had fared well during the 1800s, when the globe was still in the Little Ice Age and average temperatures were cooler. But this group weakened during the warmer 1900s, and grew more slowly as a result. Meanwhile, the second group seemed better suited for the warmer climate, and started to grow faster.
When beetle populations exploded in the 1980s, this second group mounted a much more successful battle against the bugs. After surviving the epidemic, this group of trees “ratcheted forward rapidly,” Millar explains. When an outbreak flared up in the mid-2000s, the bugs failed to infiltrate any of the survivor trees in the stand. The beetles had helped pare down the trees that had adapted to the Little Ice Age, leaving behind the ones better suited to hotter weather. Millar found similar patterns in whitebark pines and thinks it’s possible that this type of beetle-assisted natural selection is going on in different types of trees all over the country.
When Six read Millar’s studies, she was floored. Was it possible, she wondered, that we’ve been going about beetle management all wrong? “It just hit me,” she says. “There is something amazing happening here.”
Last year Six and Eric Biber, a University of California–Berkeley law professor, published a provocative review paper in the journal Forests that challenged the Forest Service’s beetle-busting strategies. After scrutinizing every study about beetle control that they could get their hands on, they concluded that “even after millions of dollars and massive efforts, suppression . . . has never effectively been achieved, and, at best, the rate of mortality of trees was reduced only marginally.”
Six points to a stand of lodgepoles in the University of Montana’s Lubrecht Experimental Forest. In the early 2000s school foresters preened the trees, spacing them out at even distances, and hung signs to note how this would prevent beetle outbreaks. This “prethinned” block was “the pride and joy of the experimental forest,” Six remembers. But that stand was the first to get hit by encroaching pine beetles, which took out every last tree. She approached the university forest managers. “I said, ‘Boy, you need to document that,’” Six says. “They didn’t. They just cut it down. Now there’s just a field of stumps.”
Six and Biber’s paper came as a direct affront to some Forest Service researchers, one of whom told me that he believes changing forest structure through thinning is the only long-term solution to the beetle problem. Politicians tend to agree—and beetle suppression sometimes serves as a convenient excuse: “It is perhaps no accident that the beetle treatments most aggressively pushed for in the political landscape allow for logging activities that provide revenue and jobs for the commercial timber industry,” Six and Biber wrote in the Forests review.
Take the Restoring Healthy Forests for Healthy Communities Act, proposed in 2013 by then representive Doc Hastings (R-Wash.) and championed by then representative Steve Daines (R-Mont.). The bill sought to designate “revenue areas” in every national forest where, to help address insect infestations, loggers would be required to clear a certain number of trees every year. Loggers could gain access to roadless areas, wilderness-study areas, and other conservation sites, and once designated, their acreage could never be reduced. The zones would also be excluded from the standard environmental-review process.
This summer, Six plans to start examining the genes of “supertrees”—those that survive beetle onslaughts—in stands of whitebarks in Montana’s Big Hole Valley. Her findings could help inform a new kind of forest management guided by a deeper understanding of tree genes—one that beetles have had for mil
lennia.
If we pay close enough attention, someday we may be able to learn how to think like they do. University of California–Davis plant sciences professor David Neale champions a new discipline called “landscape genomics.” At his lab in Davis, Neale operates a machine that grinds up a tree’s needles and spits out its DNA code. This technology is already being used for fruit-tree breeding and planting, but Neale says it could one day be used in wild forests. “As a person, you can take your DNA and have it analyzed, and they can tell you your relative risk to some disease,” Neale says. “I’m proposing to do the same thing with a tree: I can estimate the relative risk to a change in temperature, change in moisture, introduction to a pathogen.”
Right now, foresters prune woodlands based on the size of trees’ trunks and density of their stands. If we knew more about trees’ genetic differences, Neale says, “maybe we would thin the ones that have the highest relative risks.” This application is still years off, but Neale has already assembled a group of Forest Service officials who want to learn more about landscape genomics.
Six, meanwhile, places her faith in the beetles. Whereas traditional foresters worry that failing to step in now could destroy America’s forests, Six points to nature’s resilience. Asked at TEDx how she wants to change the world, she responded, “I don’t want to change the world. We have changed the world to a point that it is barely recognizable. I think it’s time to stop thinking change and try to hold on to what beauty and function remains.”
STEPHEN ORNES
The Whole Universe Catalog
FROM Scientific American
A SEEMINGLY ENDLESS VARIETY of food was sprawled over several tables at the home of Judith L. Baxter and her husband, mathematician Stephen D. Smith, in Oak Park, Illinois, on a cool Friday evening in September 2011. Canapés, homemade meatballs, cheese plates, and grilled shrimp on skewers crowded against pastries, pâtés, olives, salmon with dill sprigs, and feta wrapped in eggplant. Dessert choices included—but were not limited to—a lemon mascarpone cake and an African pumpkin cake. The sun set, and champagne flowed, as the 60 guests, about half of them mathematicians, ate and drank and ate some more.
The colossal spread was fitting for a party celebrating a mammoth achievement. Four mathematicians at the dinner—Smith, Michael Aschbacher, Richard Lyons, and Ronald Solomon—had just published a book, more than 180 years in the making, that gave a broad overview of the biggest division problem in mathematics history.
Their treatise did not land on any bestseller lists, which was understandable, given its title: The Classification of Finite Simple Groups. But for algebraists, the 350-page tome was a milestone. It was the short version, the CliffsNotes, of this universal classification. The full proof reaches some 15,000 pages—some say it is closer to 10,000—that are scattered across hundreds of journal articles by more than 100 authors. The assertion that it supports is known, appropriately, as the Enormous Theorem. (The theorem itself is quite simple. It is the proof that gets gigantic.) The cornucopia at Smith’s house seemed an appropriate way to honor this behemoth. The proof is the largest in the history of mathematics.
And now it is in peril. The 2011 work sketches only an outline of the proof. The unmatched heft of the actual documentation places it on the teetering edge of human unmanageability. “I don’t know that anyone has read everything,” says Solomon, age 66, who studied the proof his entire career. (He retired from Ohio State University two years ago.) Solomon and the other three mathematicians honored at the party may be the only people alive today who understand the proof, and their advancing years have everyone worried. Smith is 67, Aschbacher is 71, and Lyons is 70. “We’re all getting old now, and we want to get these ideas down before it’s too late,” Smith says. “We could die, or we could retire, or we could forget.”
That loss would be, well, enormous. In a nutshell, the work brings order to group theory, which is the mathematical study of symmetry. Research on symmetry, in turn, is critical to scientific areas such as modern particle physics. The Standard Model—the cornerstone theory that lays out all known particles in existence, found and yet to be found—depends on the tools of symmetry provided by group theory. Big ideas about symmetry at the smallest scales helped physicists figure out the equations used in experiments that would reveal exotic fundamental particles, such as the quarks that combine to make the more familiar protons and neutrons.
Group theory also led physicists to the unsettling idea that mass itself—the amount of matter in an object such as this magazine, you, everything you can hold and see—formed because symmetry broke down at some fundamental level. Moreover, that idea pointed the way to the discovery of the most celebrated particle in recent years, the Higgs boson, which can exist only if symmetry falters at the quantum scale. The notion of the Higgs popped out of group theory in the 1960s but was not discovered until 2012, after experiments at CERN’s Large Hadron Collider near Geneva.
Symmetry is the concept that something can undergo a series of transformations—spinning, folding, reflecting, moving through time—and, at the end of all those changes, appear unchanged. It lurks everywhere in the universe, from the configuration of quarks to the arrangement of galaxies in the cosmos.
The Enormous Theorem demonstrates with mathematical precision that any kind of symmetry can be broken down and grouped into one of four families, according to shared features. For mathematicians devoted to the rigorous study of symmetry, or group theorists, the theorem is an accomplishment no less sweeping, important, or fundamental than the periodic table of the elements was for chemists. In the future, it could lead to other profound discoveries about the fabric of the universe and the nature of reality.
Except, of course, that it is a mess: the equations, corollaries, and conjectures of the proof have been tossed amid more than 500 journal articles, some buried in thick volumes, filled with the mixture of Greek, Latin, and other characters used in the dense language of mathematics. Add to that chaos the fact that each contributor wrote in his or her idiosyncratic style.
That mess is a problem because without every piece of the proof in position, the entirety trembles. For comparison, imagine the two-million-plus stones of the Great Pyramid of Giza strewn haphazardly across the Sahara, with only a few people who know how they fit together. Without an accessible proof of the Enormous Theorem, future mathematicians would have two perilous choices: simply trust the proof without knowing much about how it works or reinvent the wheel. (No mathematician would ever be comfortable with the first option, and the second option would be nearly impossible.)
The 2011 outline put together by Smith, Solomon, Aschbacher, and Lyons was part of an ambitious survival plan to make the theorem accessible to the next generation of mathematicians. “To some extent, most people these days treat the theorem like a black box,” Solomon laments. The bulk of that plan calls for a streamlined proof that brings all the disparate pieces of the theorem together. The plan was conceived more than 30 years ago and is now only half-finished.
If a theorem is important, its proof is doubly so. A proof establishes the honest dependability of a theorem and allows one mathematician to convince another—even when separated by continents or centuries—of the truth of a statement. Then these statements beget new conjectures and proofs, such that the collaborative heart of mathematics stretches back millennia.
Inna Capdeboscq of the University of Warwick in England is one of the few younger researchers to have delved into the theorem. At age 44, soft-spoken and confident, she lights up when she describes the importance of truly understanding how the Enormous Theorem works. “What is classification? What does it mean to give you a list?” she ponders. “Do we know what every object on this list is? Otherwise, it’s just a bunch of symbols.”
Reality’s Deepest Secrets
Mathematicians first began dreaming of the proof at least as early as the 1890s, as a new field called group theory took hold. In math, the word “group” refers to a set of objects
connected to one another by some mathematical operation. If you apply that operation to any member of the group, the result is yet another member.
Symmetries, or movements that do not change the look of an object, fit this bill. Consider, as an example, that you have a cube with every side painted the same color. Spin the cube 90 degrees—or 180 or 270—and the cube will look exactly as it did when you started. Flip it over, top to bottom, and it will appear unchanged. Leave the room and let a friend spin or flip the cube—or execute some combination of spins and flips—and when you return, you will not know what he or she has done. In all, there are 24 distinct rotations that leave a cube appearing unchanged. Those 24 rotations make a finite group.
Simple finite groups are analogous to atoms. They are the basic units of construction for other, larger things. Simple finite groups combine to form larger, more complicated finite groups. The Enormous Theorem organizes these groups the way the periodic table organizes the elements. It says that every simple finite group belongs to one of three families—or to a fourth family of wild outliers. The largest of these rogues, called the Monster, has more than 1053 elements and exists in 196,883 dimensions. (There is even a whole field of investigation called monsterology in which researchers search for signs of the beast in other areas of math and science.) The first finite simple groups were identified by 1830, and by the 1890s mathematicians had made new inroads into finding more of those building blocks. Theorists also began to suspect the groups could all be put together in a big list.
Mathematicians in the early 20th century laid the foundation for the Enormous Theorem, but the guts of the proof did not materialize until midcentury. Between 1950 and 1980—a period which mathematician Daniel Gorenstein of Rutgers University called the “Thirty Years’ War”—heavyweights pushed the field of group theory further than ever before, finding finite simple groups and grouping them together into families. These mathematicians wielded 200-page manuscripts like algebraic machetes, cutting away abstract weeds to reveal the deepest foundations of symmetry. (Freeman Dyson of the Institute for Advanced Study in Princeton, New Jersey, referred to the onslaught of discovery of strange, beautiful groups as a “magnificent zoo.”)
