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Can the tree whisperer save our forests?

by Portal Web Editor last modified Mar 01, 2013 06:26 PM
Contributors: Nikiforuk, Andrew
© 2010-2011 Postmedia Network Inc
Driven by a warming climate and human intervention, hordes of tiny beetles have devastated North America's great forests over the past 20 years. In this edited excerpt from his new book, Calgary author Andrew Nikiforuk examines how one quirky homemade invention provided some insight into ways of controlling a seemingly unstoppable beetle outbreak
Can the tree whisperer save our forests?

A Pine beetle and larvae at the Northern Forestry Centre in Edmonton.

Original Source

Driven by a warming climate and human intervention, hordes of tiny beetles have devastated North America's great forests over the past 20 years. In this edited excerpt from his new book, Calgary author Andrew Nikiforuk examines how one quirky homemade invention provided some insight into ways of controlling a seemingly unstoppable beetle outbreak

During 2005, David Dunn often wandered the hilly outskirts of Santa Fe looking like a medieval plague doctor. Armed with headphones and a tape recorder, the avantgarde music composer and violin player poked the thin bark of pinyon trees with a special homemade device.

The odd contraption consisted of a meat thermometer and a piezoelectric transducer from a Hallmark greeting card. After inserting the modified thermometer-cum-microphone into the tree's inner bark, Dunn patiently listened to the voices inside the tree. The bespectacled artist made an ungainly apparition in the desert forest as he perched against trees for hours on end.

Dunn became a tree whisperer after New Mexico started to lose half of its famed pinyon trees to an unprecedented beetle outbreak. Anxious landowners wanted a clear diagnosis on their trees before they pulled out their chainsaws.

Because Dunn had the listening tools, he got recruited for the job. Whenever the sound engineer heard noises that resembled running water or creaking winds in a pinyon, he'd give the tree an all-clear for beetles. Such a diagnosis inevitably invited two possible prescriptions: the landowner could water the tree more often, to build resin resistance, or he or she could spray the pinyon with the pesticide carbaryl. If Dunn heard squirrel-like pops and clicks, that meant the beetle had taken up residence and was now building its own magical sound universe.

Such a diagnosis invariably resulted in someone pulling out a saw. When people offered to pay for his unique service, Dunn gracefully accepted a donation on behalf of his non-profit Art and Science Laboratory. Dunn, after all, was collecting data on one of the world's most remarkable animals for one of the strangest and most unlikely of science experiments.

Dunn's otherworldly investigation began in summer of 2003, when clouds of Ips confusus alighted on the pinyons. The beetles turned the trees a deathly ocher, and then a Halloween gray. The musician's neighbors started to panic, but Dunn got curious and cobbled together his odd-looking microphone. "I felt there was an exceptional amount of biological activity going on, and I wondered if there would be any sound in the tree," he recalls. He discovered a richer acoustical world in pinyons invaded by polygamous beetles than he could have ever imagined. It was like encountering a skilled percussion group in the middle of the Mojave Desert. All the clicks and pops prompted the illustrious artist to ask a series of questions that scientists rarely ask.

Dunn started with the stories of Pueblo elders, who believe that "the beetles come when the trees cry." He wondered if that was true, and, if so, how a pinyon might weep. He was also curious about how bark beetles communicated in their winding galleries. Why did scientists know so little about the insect's acoustic abilities? Could the death of beetle-riddled spruce trees in Alaska be related to the pinyon-killing drought in New Mexico? His list kept growing.

Ips confusus, the innocuous pinyon engraver, set Dunn off on a seven-year investigation into scolytids, climate, beetle music, and complexity.

Dunn's reflections produced some radical conclusions. Given the insect's evolutionary success and its ability to change entire landscapes at the drop of a hat, Dunn thinks bark beetles might be one of the most important animals on earth. "They are amazing creatures. They eat themselves out of a food source. That's a terrifying proposition." After producing a highly unusual beetle CD called The Sound of Light in Trees, Dunn began a wildly inventive collaboration to test an innovative idea: acoustic warfare against beetles. The results could change the entire field of pest management. "We altered beetle behavior by playing back their own sound," explains Dunn. "We managed to turn them into cannibals. We created unprecedented behaviors."

Ips confusus doesn't normally go on wild killing sprees. Tellingly, Stephen L. Wood gives the creature scant mention in his scolytid bible. Unlike the predatory mountain pine beetle, the Ips is an opportunist that takes out individually stressed or injured pinyons. The male leads the attack and then is joined by four or five females along with the usual crew of mites, nematodes, and strains of fungi, including the classic bluestainers. Ips larvae primarily feed on the phloem of the tree and carve long-winding galleries under the bark.

A good drought, however, threw both trees and beetles off balance. The dry spell descended on the Southwest in the mid-1990s, after twenty years of wet weather, and didn't let go until 2005. At the Los Alamos National Laboratory, ecologist David Breshears could look out his window at a pinyon study plot the size of a football field and actually watch the trees die. "I would see the trees go from vibrant green to pale, gasping green to pale brown to dropping all their needles," he remembers. Between 2002 and 2003, the die-off was so extensive that patches of graying trees could be seen from outer space. It extended over 4,600 square miles, an area the size of Germany's Black Forest.

Drought-stressed pinyons gave the engraver beetle an opportunity to run riot in a landscape of undefended castles. The mild-mannered Ips normally reproduces two generations a year. During the drought, some populations reproduced as many as five times annually. "There was an exponential explosion," explains David Dunn. In 2003 alone, the outburst reached an Alaskan scale, covering 800,000 acres in four states.

The Ips storm was unlike anything entomologists had seen before. Mike Wagner, a jovial, ruddy-faced researcher at Northern Arizona University, found engravers as thick as Canadian blackflies just ten miles outside of Flagstaff. "I was on a field trip in the forest, and every time I opened my mouth a bark beetle would fly into it," says Wagner. It was like an insect hurricane blowing through the mesa. Hundreds of beetles would bore into the boles of the pinyon, and thousands of their offspring would emerge shortly afterward to attack new trees. The populations grew so dense that not a living pinyon of any age remains.

By the time the beetles approached David Dunn's home in Santa Fe, they had finished off 55 million drought-stressed trees, 10 percent of the state's forests. Although Dunn knew little about beetles or their acoustic life then, he already understood that the natural world was startlingly musical. In 1990, he had released underwater recordings taken from insect activity in ponds. The creatures, including a variety of water beetles, made wild tropical-like rasps and sputters.

As Dunn's CD amplified, insects do a lot more talking than scientists initially thought. With the aid of sensitive digital technology, researchers can now hear insects rubbing together a variety of body parts (an act called stridulation) to make a host of unique sounds. A recording of two thousand eastern subterranean female termite workers, for example, sounds a lot like a dentist working on a tooth cavity. The sounds made by palm weevil larvae call up the image of a dyslexic Morse code operator.

At first, Dunn had thought that bark beetles were a largely mute group. But then the musician came across a series of interesting studies on mountain pine beetles done in Oregon in the 1970s by Joseph Rudinsky. Rudinsky found that courting males struck up an aggressive chirp to attract mates or to ward off rivals. They did so by rubbing a sound organ on the back of their heads, called a pars striden, against the main part of their bodies.

Dunn had the idea of retrofitting a ten-dollar meat thermometer to act as a microphone, with the hollowed shaft serving as a wave guide. The piezobender disc, taken from a greeting card, acted as loudspeaker. Dunn, who now exports this beetle listening device to Chinese researchers, first planted the tool in the phloem layer of a pinyon tree by his home in early spring of 2003. He recorded silence. The tree creaked in the wind, but that was it. After temperatures got warmer, he waited two weeks and then tried again. This time, he heard stirrings, pops, chirps, and clicks. The phloem and cambium layers of a pinyon tree "are an amazingly effective medium for acoustic communication," he says. Over the next two years, Dunn made recordings at hundreds of pinyon trees. He was able to do something few beetle academics have done: listen unhurriedly to the deliberate and chatty work of scolytids in the wild.

Some days Dunn inserted his recorder near nuptial tunnels, other times near pitch tubes. He discovered that stridulation "can go on continuously for days and weeks," long after the beetles have mated and excavated their tunnels. All of this talking suggested to Dunn that the beetle not only had "a more sophisticated organization than previously suspected" but also used perfume trails for long-distance communication in the forest, then switched to stridulation for short-distance chats inside trees. In fact, he discovered, the beetles created an endless chatter in young and old trees at almost every time of the year except winter. "The beetles weren't even quiet at the end of summer."

Dunn noted the condition of the trees he tested, recording the color of their needles and the number of pitch tubes on the trunk. On severely stressed trees, the beetles bored through bark without encountering any resin resistance at all, noted Dunn. Trying to save an attacked tree seemed futile, since "it doesn't take long for a beetle to take a tree down."

Dunn discovered during his investigations that pinyon trees several hundred years old appeared to have an entirely different relationship with the beetle than did younger trees. Most of the elders had survived previous beetle visitations and had some sort of resilience. Some of their branches thrived though others seemed dead. But big concentrations of beetles still settled in these old trees. "Their behavior [there] was entirely different, as though they had entered an equilibrium state. They hadn't killed the tree but had established themselves. It was though something else was going on," Dunn recalls.

The trees made their own sad music. A parched pinyon typically produces a variety of powerful pops that sound like distant drumbeats. Botanists call this collapse of cells "cavitation" and use it as a measure for drought stress. Healthy trees pump water from their roots to needles via a series of pipes in the xylem. The system works under negative pressure. During a drought, air bubbles form in this vascular system, creating a sort of tree thrombosis. The cells eventually collapse with a popping sound. "They can implode with such tremendous instantaneous force that, under laboratory conditions, they have been measured to produce temperatures up to five thousand degrees centigrade," says Dunn. As the Pueblo put it, the beetles hear a tree crying in an arid land.

The Sound of Light in Trees, the CD Dunn made from his recordings, showers listeners with bizarre beetle sounds. Alien clicks and rude tweets seemingly rise above an orchestral background of drying wood. The stridulations of the Ips beetle sound alternatively subterranean and watery. Many of the squeaks and clicks call to mind an old man sitting in a rocking chair in another room, cleaning his briar pipe with a shank brush.

About the same time as David Dunn was making his beetle recordings, Reagan McGuire, a fifty-six-year-old truck driver, pool hustler, and genuine character from Pittsburgh, read an article about bark beetles killing 74 million trees in Arizona and New Mexico. "I thought that was a lot and wanted to do something about it. I'm a tree hugger. I love trees," McGuire says. He recalled how the U.S. military had blasted Panama dictator Manuel Noriega out of his refuge in the Vatican embassy by playing heavy rock music day and night. (The blasting also drove the Vatican crazy.) Similar longrange acoustic devices were used to deter Somali pirates. McGuire, a freethinker, wondered if he could create the same kind of acoustic stress in a bark beetle. He called up Richard Hofstetter, the young beetle specialist at the University of Northern Arizona in Flagstaff. Hofstetter listened during a meeting with McGuire, though "he looked at me as though I was crazy," McGuire recalls. McGuire kept going back. Eventually Hofstetter, who studies the mites and fungi on the beetle bus, found some money and put McGuire to work in a lab at the university's forestry building. Given the dismal history of bark beetle control, Hofstetter reckoned it wouldn't hurt to try something completely different.

While doing background research, McGuire came across Dunn's Sound of Light in Trees and shared it with Hofstetter. The incredible range of chirping sounds convinced Hofstetter that the bark beetle had a much more complex way of communicating than previously thought and that McGuire wasn't crazy after all. McGuire visited Dunn for a week to learn how to record beetle sounds in trees. The two often talked through the night about beetles, music, aridity, and life. Since then, the entomologist, the musician, and the pool hustler have collaborated on one of the craziest science experiments in insect history.

In his lab, Hofstetter fashioned a "phloem sandwich" so McGuire could view his beetle subjects while filming and recording their reactions to different sounds. This beetle version of an ant farm consists of two plates of Plexiglas with a piece of sugar-rich phloem in between. Although the phloem dries out quickly, the sandwich gives researchers a clear view of beetles doing their thing.

To start off the experiments, McGuire played the most abrasive sounds he could think of: heavy metal and, amusingly, angry monologues by Rush Limbaugh, the infamous talk-radio host. "I wanted an authoritative, agitating, and repeatable voice I could play back again and again. I also wanted to stress the hell out of the beetles, and I thought that hate radio would do it," McGuire explains.

But the beetles in the phloem sandwich ignored Limbaugh's bombast. The beetles didn't react, either, when McGuire played the man's voice backward. "They're smart critters," adds McGuire. The beetles also ignored head-banging tunes by Metallica, as well as Guns n' Roses' Welcome to the Jungle.

Hofstetter then proposed that the team try playing more beetle-like sounds. That's when things got really interesting. They first put a female pine beetle in the sandwich and then introduced a male to the entry hole. The male promptly stridulated with a chirp sound saying "I'm here. I'm here." Then McGuire played the sound of another male chirping. The female promptly abandoned the real male in a vain attempt to find the louder but virtual source. "In one case, she tunneled to the speaker and waited. We changed their reproductive behavior completely," says Hofstetter.

Another experiment highlighted the power of bark-beetle voices in a grim way. Both Hofstetter and Dunn wondered why there were no hybrid beetles in Arizona, given that the western and the southern pine beetle often attack the same ponderosa tree. To find out, they parked a female western bark beetle in a phloem sandwich, then introduced a male southern pine beetle. "The female started signaling by making weak pulsing sounds. The male moved towards her and started to make a terrifying loud stridulation sound. The female froze in her tracks. Then the male came up to her and chewed her in half lengthwise. It was sonic warfare," says Dunn.

After McGuire had recorded and modified the squirrel-like screech of the male southern pine beetle, he played it back to a pair of western pine beetles. He watched a male mate with a female two or three times and then suddenly chew her to pieces. "You know, you don't see that in nature. That's not natural." In another study, a desperate southern pine beetle male chewed his way through the Plexiglas. He continued for two weeks after McGuire stopped playing the sound. "His mandibles were reduced to stubs," says McGuire. "It was extraordinary."

If beetle sounds can defeat scolytids and temper their forest-eating behaviors, Hofstetter's team could change the course of entomology. Instead of poisoning termites, ants, cockroaches, and other pests, people might limit these tidy empires with sonic fences or disrupt their mating practices with horrific insect yells and shrieks. Protecting stored grain supplies could become as simple as flipping a switch. "Acoustic ecology could change the way we do pest control," admits Hofstetter.

Dunn doesn't know where the bark beetle will take his own art or how the insect will ultimately redesign the earth's forests and climate. He hopes that sonic warfare will eventually calm the beast in the forest. But the artist knows that he has surely met a charismatic creature like no other, a Beethoven among insects. If nothing else, the beetle should remind us, says Dunn, that we are all part of nature; we come from the natural world and will live or die depending on our generous understanding of that world. Like the Babylonian beetle empires now rising and falling in our forests, human civilization has abruptly experienced collapse, and will again. The problem with nonlinear change (and neither human nor bark beetle empires move in a straight line) is that "there is no off switch," says Dunn. "We can't reboot the software." He suspects that the sound of the beetle in droughtwounded trees heralds profound transformation. He pauses before he adds a final thought. "The changes probably won't be good for us."

 

 
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