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Bay Nature magazineOctober-December 2016

The Burning Question in the East Bay Hills: Eucalyptus Is Flammable Compared to What?

Twenty-five years after the Oakland Hills fire, people still disagree about whether blue gum eucalyptus is a fire threat in the East Bay Hills

by Zach St. George on October 18, 2016

Illustration by Maggie Chiang
Illustration by Maggie Chiang


he gums are mottled tan and brown like chicken bones, crowded together, the spaces between them choked with brush and hung with streamers of bark. Along with the sweet medicine smell of the trees, there is the warm scent of sawdust and a sour hint of exhaust. I’m with Brad Gallup, a fire captain with the East Bay Regional Park District. We’re deep in Tilden Regional Park, standing on a fire road between a feller buncher and a chipper. It’s his job to make sure that if and when this forest burns, it doesn’t take half of Berkeley with it.

In front of us on the uphill side of the road is what looks like a group of seven trees but is really a single tree with multiple boles. Like many of the trees in this forest, it was cut after the hard frost of 1972. Tasmanian blue gums, Eucalyptus globulus, don’t like cold. But the frost didn’t really kill the trees, only made them retreat back down into their roots. The workers who cut the trees then didn’t treat the stumps with herbicide, and now they’re regrown, more trunks and closer together.

The ground below this tree is littered with its rooster-tail leaves and cinnamon-stick tubes of bark. More bark peels from the trunks and spills out from piles built up in the valleys between them. Gallup considers the gum, buried in a pyre of its own debris. “That’s a great way to get the tree to burn,” he says. “Like, you couldn’t come up with a better way to get that tree to burn.” This tree is surrounded by others just like it; this grove just one of the dozens between here and Lake Chabot, millions of blue gums billowing from the ridgeline like sage-green smoke.

The 1991 Tunnel Fire in the Oakland Hills, which killed 25 people and destroyed more than 3,000 homes, confirmed for many people what they had long suspected: Eucalypts are a hazard. Though the fire started in grass, the trees were blamed for the severity of the disaster, by some estimates contributing almost three-quarters of the fire’s energy. Last year, after a decade of planning and legal hurdles, the Federal Emergency Management Agency approved a $5.7 million fire prevention grant to UC Berkeley, the City of Oakland, and the East Bay Regional Park District—the major land managers in the hills area—to thin and remove trees and brush on 1,000 acres of ridgeline between Wildcat Canyon and Anthony Chabot regional parks; the park district will thin another 1,000 acres. Of those 2,000 acres, roughly 800 are dominated by blue gum—representing perhaps a quarter of the East Bay’s eucalyptus. The Hills Conservation Network, a small Berkeley nonprofit whose members live in the area covered by the FEMA grant, promptly sued FEMA to stop the grant, focusing in particular on roughly 350 acres of Oakland and UC Berkeley property in Claremont Canyon and Strawberry Canyon and around the Caldecott Tunnel, where all nonnative trees—predominately eucalyptus—would be removed. It argued that clearing trees would actually make the hills more flammable.

“Every piece of vegetation is flammable. It’s not just eucalyptus we target. We target grass. We target brush.”
-Brad Gallup, EBRPD fire captain

hat is ostensibly a debate about fire science is more than that, though—it is really just the latest episode in a decades-old dispute over the Australian trees’ place in the Bay Area. There are plenty of people who simply like the trees for their own sake, but the debate is also about deeper questions, like what it really means for a species to be native or nonnative, what really constitutes natural, and even whether it is hubris to imagine that humans can break our habit of wreaking unintended consequences. The original question—whether blue gums are uniquely, dangerously flammable—often serves as proxy to these other debates. But it is plenty complicated on its own.

Gallup is characteristically diplomatic. “Every piece of vegetation is flammable,” he says. “It’s not just eucalyptus we target. We target grass. We target brush.” He studied forestry and says he can understand the attachment people feel. “I love trees,” he says. At the same time, anyone who’s fought a fire in eucalyptus understands why they need to be thinned, he says—all vegetation will burn, that’s true. But some of it burns better. From the brush down at the bottom of the gully, there is the whine of a chain saw.

The aftermath of the tunnel Fire in the Oakland Hills, fall 1991. [Oakland Fire #12-91.] (Photo by Richard Misrach, courtesy Fraenkel Gallery, San Francisco, Pace/MacGill Gallery, New York, and Marc Selwyn Fine Art, Los Angeles)

The aftermath of the tunnel Fire in the Oakland Hills, fall 1991. [Oakland Fire #12-91.] (Photo by Richard Misrach, courtesy Fraenkel Gallery, San Francisco, Pace/MacGill Gallery, New York, and Marc Selwyn Fine Art, Los Angeles)


ome 600 members of genus Eucalyptus dominate forests across Australia. There, the debate isn’t over whether the trees are flammable, says David Bowman, a fire ecologist at the University of Tasmania, but about whether the trees have simply evolved to survive fire, or whether they actually promote fire as a way to snuff out competitors. “It’s an amazing just-so story,” he says of the possibility: “Eucalypts evolved to burn their neighbors.”

It’s clear that fire benefits the trees. “For most eucalypts, fire was not a destroyer but a liberator,” writes fire ecologist Stephen Pyne in his book Burning Bush. Many species of eucalyptus both tolerate fire, hiding from the flames behind thick bark, and depend on it to open their seed pods. Fire often even seems to have a rejuvenating effect on the trees. After a fire, many eucalypt species will sprout epicormic shoots along their entire trunks. In the event that a fire does destroy the aboveground parts of the tree, it can send up new shoots from lignotubers, nutrient-filled organs hidden among its roots.

But it’s not clear whether the eucalypts simply evolved to weather fire, or whether they actually promote fires. Bowman says the burn-your-neighbors theory, inspired by a 1970 paper by American forester Robert W. Mutch, suggests intent: By this reading, the eucalypts’ oil-rich leaves evolved to ignite easily; their peeling bark evolved to be carried aloft by the wind off a fire, spreading the blaze; they evolved to resprout quickly after a fire from both seed and shoot not just because they evolved in a landscape that burns frequently, but because, in some flori-sadomasochistic way, they want to be burnt.

As intriguing as the theory is, Bowman thinks it goes too far, failing the Occam’s-razor test: It’s simpler to imagine that eucalyptus evolved with oily leaves because those oils deter insects and koalas; they evolved peeling bark because the falling bark takes parasitic epiphytes with it; and the trees quickly resprout en masse after fire because they’ve evolved to tolerate fire, not to enjoy it. Like the other Australian fire ecologists and eucalyptus experts I spoke with, though, Bowman called the genus in general, and blue gum in particular, extremely flammable. “They’re absolutely dangerous plants,” he says. It’s not personal. “I love eucalyptus,” Bowman says. “The forests are beautiful. You get away from stress, smell the smells, see the birds. But then they catch on fire.”

“The forests are beautiful. You get away from stress, smell the smells, see the birds. But then they catch on fire.”
-David Bowman, University of Tasmania fire ecologist

In the Bay Area, though, it’s not enough to just say the blue gums are flammable, Dave Maloney points out as we drive from Walnut Creek toward Berkeley. Many of the hills on the east side of the Caldecott Tunnel are covered in grass, speckled with drooping oak, much as the landscape above Berkeley and Oakland would’ve looked before Oakland developer Frank Colton Havens planted them with eucalyptus. We pass through the tunnel and drive into the hills. Thickets of eucalyptus spring up on either side, their leaves and bell-shaped nuts cluttering the roadside. We stop at a turnout and hike up a path through tall grass that opens into a field. In the middle of the field is a pile of eucalyptus logs, surrounded by waist-deep thistles and grass. The real question, Maloney says, is “flammable compared to what?”

Maloney is a retired firefighter. He is among the pro-eucalyptus faction’s star fire authorities, although his expertise, he admits, is not in wildland fire. He was head of fire prevention at the U.S. Army base in Oakland at the time of the 1991 fire and was one of several dozen people on the Forestry and Revegetation subcommittee of the Task Force on Emergency Preparedness and Community Restoration, convened by Mayor Elihu Harris of Oakland in 1992. He says the FEMA plan ignores both the task force’s findings and good sense—that removing the trees would actually make the hills more liable to burn, as exemplified by this field, once covered in blue gums, now thick with grass and thistles.

Grass and brush will catch fire more easily than a tree, Maloney says. It’s the same reason that crumpled newspaper will ignite more easily than a log—a fire requires oxygen, heat, and fuel, and grass and balled-up paper are airier and easier to heat to the point of ignition. (It’s also why, even in the hottest fire, it’s almost always a tree’s branches and leaves burning, not its trunk.) Because its components are easier to ignite, a grass fire can also spread much faster than a fire in trees. Second, Maloney says removing the eucalyptus would also remove windbreaks.. In many parts of the state, people planted eucalyptus for that express purpose; the wind inside a forest might have less than half the wind speed it would in the open. In the same way that blowing on a campfire will rouse the coals, wind increases the amount of oxygen to a fire and hastens its spread. Finally, Maloney says, cutting the trees would make the hills drier, both by increasing the amount of sun hitting the ground and because the trees collect condensation on their leaves. Trees near the ridgeline can collect inches of fog-drip a year, sometimes even rivaling the amount they might collect from rainfall.

Related: How did the Australian eucalyptus come to the Bay Area? The story of a 19th-century capitalist and his surprising legacy.

We drive next to Signpost 29, for another view of the possible future. In the early 2000s, UC Berkeley and the nonprofit Claremont Canyon Conservancy cleared 70-odd acres on the south side of Claremont Avenue. Now it is regrown with native willows, bays, oaks—the species that advocates of the FEMA plan insist will, with some human help, replace the eucalypts—as well as redwoods, nonnative thistle, fennel, and broom. It looks scrubby and multitextured compared to the stand of blue gum across the road. For advocates of the FEMA plan, Signpost 29 is a good example of what will happen when eucalyptus is removed; to their opponents, it is a prime example of the folly in removing the trees. As we walk the downhill side of the road, Maloney points out what he sees as potential hazards: dry wood chips, brush that should be cleared out, a thistle-covered hillside, more sun, more wind. “This in here is a disaster waiting to happen,” he concludes.

I visited Signpost 29 three times while reporting this story. Although the view didn’t change, I saw something different each time through the eyes of the person I was with. Here, the debate about the flammability or fire danger of an entire forest is reduced to its smallest, most arcane variables, starting with leaf chemistry. The Vicks VapoRub smell of blue gum forests comes from the oils in their foliage, oils that fire ecologist consultant Carol Rice says can be as much as a fifth of a eucalyptus leaf’s dry weight. Oil has a higher energy density and lower ignition point than cellulose (the stuff plant cell walls and Mini Wheats are made of), and in a hot fire, these oils can boil out of the leaf and then ignite, which is why blue gums have a reputation for exploding. Euc-defenders point out that the leaves of native California bay laurel trees also have a high oil content. Yet Rice, who helped plan UC Berkeley’s portion of the FEMA application, says that factor is mitigated by the higher moisture content of bay laurel leaves.

From unclear comparisons of leaf chemistry, we are led down progressively less rewarding or elucidating scientific rabbit holes. The high oil content of eucalyptus leaves also means that they burn hotter than less oily leaves. After an extensive search, I came up with four studies that concluded blue gum leaves have a heating value of about 10,000 BTU per pound, which is a little less than coal and about 1,500 BTU more than your average plant material. But again, this is not necessarily more than native species—for example, coyote brush, an early-succession bush that could replace eucs in unshaded areas, has a heating value of about 8–10,000 BTU per pound, depending on the time of year. (For context, a single kitchen match is worth about one BTU.)

Ignitability—how easily something catches fire—is a combined result of its architecture, chemistry, moisture content, and caloric values. Like dry grass, blue gum leaves have a high surface-area-to-volume ratio and tend to build up in well-aerated piles. But, as with the BTU comparisons, there are few applicable apples-to-apples (or blue-gums-to-bay-laurels) studies of ignitability in the Bay Area. Jack Gescheidt, a fervent euc-defender and photographer who makes pictures of nudes posing with trees, told me that he conducted an informal test, lighting both wet and dry leaves from blue gum and bay laurel trees over his stovetop. At his urging, I did the same. The wet leaves didn’t burn, but the dry leaves of both species flared impressively and smoked up my apartment.

But there is no peer-reviewed version of my informal test. According to both the FEMA environmental impact statement and a 2016 study of blue gums in California by ecologist Kristina M. Wolf and biologist Joseph M. DiTomaso, blue gum has an ignition rating of 1 out of 10, with one being the most easily ignited. Grass also earns a 1, while oak/bay woodland earns a 6 and scrub vegetation earns a 4 to 8. To find out where that rating came from, I followed a twisted path from document to document, each taking me a little further back in time. Both the FEMA impact statement and Wolf and DiTomaso’s study list the source of the ignitability rating as a 2009 wildfire hazard reduction and vegetation management report by California-based environmental consultants LSA Associates, prepared for the East Bay Regional Park District. LSA Associates’ source, in turn, is a 1995 report by Amphion Inc. on the proceedings of a meeting by the Vegetation Management Consortium (which later became the Hills Emergency Forum), a group of local fire management stakeholders and experts. Rice was a participant at the 1995 meeting. I asked her why the consortium gave blue gum a high ignitability rating as well as a high hazard rating—what studies was that based on? It wasn’t based on any specific studies, she told me, but was rather an agreement among the experts—as she recalled it, a sort of, “This is what we think. What do you think?’”

“Eucalyptus is flammable. But the thing that’s most concerning is the volume of material it can produce.”
-Scott Stephens, UC Berkeley fire ecologist

bout a month after my visit to Signpost 29 with Dave Maloney, I return with Dan Grassetti, founder and director of the Hills Conservation Network, the nonprofit that’s filing suit against FEMA. A tech entrepreneur, Grassetti lives in the hills near Claremont Canyon. Like Maloney, he says he got involved after researching the FEMA plan and coming to the conclusion that removing trees would make the area more fire prone, not less. We walk uphill along Claremont Avenue, then hike up into the eucalyptus grove. This is one of the areas owned by UC Berkeley, where all of the eucalypts would be removed. The gums tower over us. Underneath are small oaks, bays, and smaller shrubby native species. Though it was sunny and beginning to get warm on the downhill side of the road, here it is cool. The ground is muddy. When the wind stirs the boughs, drops of last night’s fog rain down on us.

Near the crest of the hill, we come upon a large blue gum with seven boles. “This is my favorite tree,” Grassetti says, giving it a slap on the trunk. “This one I made a promise to, that I was not going to let any harm come to it. I’m going to live up to that promise.” The ground around the tree is littered with its bark and leaves, inches deep in places. If there is a single factor that makes the blue gums a fire hazard, it is this.

Andrew Sullivan, a bushfire expert at the Commonwealth Scientific and Industrial Research Organization in Canberra, says that in Australia, dry eucalypt forest might accumulate eight to 12 tons of debris per acre. Like the other Australians I spoke with, Sullivan called the Bay Area blue gums “supersized,” treated to better soils than those in nutrient-poor Australia and untrimmed by their native pests. Its native decomposers are missing too, meaning fallen leaves and bark decay slower than usual; here, eucalyptus groves can accumulate 30 tons of debris or more per acre. According to a 2006 National Park Service study, that’s compared to California bay laurel trees, which average 18 tons per acre, and coast live oaks, which average just 11; an acre of grass, meanwhile, contains somewhere between one and four tons of plant material. Furthermore, the majority of the blue gum litter is small sticks, bark, and leaves, collectively known as “fine fuels.” These fine fuels are the source of a forest fire’s power, Sullivan says, easily ignited and quickly consumed. “Eucalyptus is flammable,” says Scott Stephens, a UC Berkeley fire ecologist. “But the thing that’s most concerning is the volume of material it can produce.”

But now, standing by Grassetti’s favorite tree, even this most damning of blue gum statistics seems woefully abstract. “Yes, there is some fuel here,” Grassetti says, then gestures to the head-high brush that surrounds us. “But there’s a lot of fuel there, too. If you cut down these trees and eliminate this source of fuel, well, what’s going to happen? That stuff”—the brush—“is going to expand here. So did you really get a net fuel reduction? I would argue that at best—at best—you broke even.” With inexpert eyes, I look at the brush and trees and debris, and try to imagine how it all might burn. To really know with scientific certainty, you’d have to compare fuel moisture content, wind speed, leaf chemistry, caloric content, and ignitability. We walk back down the hill, sliding in the mud.


n the middle of June, I attended a protest outside the Sierra Club’s national headquarters in downtown Oakland. The 20-odd protesters—mostly white, mostly gray-haired—marched in a circle, holding up hand-lettered signs and photographs of butterflies and trees. “Two, four, six, eight,” they shouted. “Save the eucs because they’re great!”

Broadly, the protest was about the Sierra Club’s perceived hypocrisy; the environmentalist organization is also suing FEMA as a sort of countersuit to the Hills Conservation Network’s pro-euc suit. The Sierra Club suit argues that the plan should remove more nonnative trees, that leaving eucalyptus and Monterey pine standing would mean prohibitively expensive maintenance, and that removing the trees would allow native species to flourish.

It was immediately clear that the debate over the blue gum’s flammability is only one of several parallel conversations around the tree; while that is the Hills Conservation Network’s primary focus, it was not necessarily what most interested the individual protesters or their opponents. Several of the people I spoke with were worried about the use of herbicide as a way to keep the eucalyptus from resprouting. Overall, the FEMA plan calls for about 2,500 gallons of glyphosate herbicide (a possible carcinogen), or approximately 2.5 gallons per acre, to be applied to stumps. Others were concerned that the FEMA plan was cover for native species restoration advocates. Still others argued that removing any trees would be irresponsible in an age of climate change, and that native trees would not be able to take up the slack. Their concerns echoed some of those of the 13,000 people who wrote comments on the first draft of an environmental impact statement FEMA prepared ahead of the grant.

On the other side of the debate, the Bay Area’s many native plant advocates have their own long list of complaints, also mostly separate from the debate about the trees’ flammability. They call the eucs bad neighbors. Although blue gums tend not to invade new territory, they are salt-the-earth occupiers: Along with shading out other species, their leaf litter leaches chemicals that suppress growth of native plants, even after the trees are removed. “Those areas are really hard to restore,” says Lech Naumovich, a local restoration ecologist and consultant who has worked extensively in Claremont Canyon. Native plant advocates also argue that the trees are inhospitable to many native animals and generally reduce biodiversity in areas they dominate. Native plants, on the other hand, having evolved here over millennia, are better adapted to local conditions, they say.

My third visit to Signpost 29 is with Jerry Kent. A former assistant general manager for the East Bay Regional Park District, Kent is now on the board of directors at the Claremont Canyon Conservancy, which worked with UC Berkeley to convert the downhill side of the road to native vegetation. He has also independently researched the costs of eucalyptus removal and management. Kent and I walk the same path that I took with Grassetti and Maloney. By his reading, everything good about the eucalyptus across the street is matched or exceeded by the native species on this side: The native species are less flammable, use less water, collect fog, block wind, and provide more valuable habitat. Perhaps as important, Kent says, this side is cheaper. Leaving the eucalyptus as-is endangers thousands of homes and people and isn’t a viable option, he says. And in the bigger picture, simply thinning the trees, as the park district is doing on their properties, isn’t a great solution either. It would preserve a virtual monoculture and would require continual management that he believes could cost the East Bay Regional Park District alone hundreds of millions of dollars over the lifetime of the trees—and that’s if there are no fires to help the eucs regenerate. By contrast, the trees would only need to be cleared and the stumps treated with herbicide once, he says. It might look bad for a while, but with proper management nonnative grasses and brush would be replaced in a decade or two in most areas by native trees, he says. “Within a very short time, you have a self-sustaining, low-cost native forest.”

The protestors I spoke with disagree with Kent: They tended not to believe that the eucalyptus are more flammable or fire-promoting than native species, and they seemed determined to discount any evidence suggesting otherwise, arguing, as Maloney has, that whichever of the tree’s characteristics might promote fire are outweighed by its services. They point me repeatedly to both the 1992 Oakland mayor’s task force report and a 2013 report by the U.S. Forest Service’s Adaptive Management Services Enterprise Team. While the forest service report describes the blue gums as “highly flammable,” both documents advise against removing all of the trees in any area, for exactly the reasons that Maloney cites.

Still, both documents say there is a fire hazard. So do all the experts I spoke with, including the ones with no prior knowledge of the FEMA grant. The roughly two dozen Australian and American wildfire experts, eucalyptus experts, and fire ecologists I communicated with while reporting this story (the majority of them with no personal connection to the local debate) were unanimous in their verdict: Blue gum eucalyptus is especially, dangerously flammable. “Anybody who wants to encourage really flammable plants in an urban mix has to do it with their eyes open,” David Bowman told me. There is no single, knockout paper or study that shows that blue gums are drastically more dangerous fire-hazards than other local species, that’s true, but that’s probably too much to ask anyway. Ross Bradstock, a wildfire expert at the University of Wollongong, says that while being able to empirically compare the flammability of different trees would be useful, it’s not currently possible. Leaves or other components, meanwhile, can tell you only so much about the whole, and individual trees only so much about the forest. “We’re in our infancy in understanding how flammability can be practically measured and scaled up,” he says.

“We’re trying to change fire behavior, to make it easier to put the fire out, to give people more time to evacuate.”
-Brad Gallup

ow imagine a fire. Not just any fire, but the fire, the fire that all this is about. It’s late September, in a eucalyptus grove on the ridgeline above the UC Berkeley campus. The grove is one of those that were logged off after the 1972 freeze, and the trees grew back just a few feet apart, hung with bark and knee-deep in fallen leaves, bark, and twigs. For most of the year, these trees would collect fog and slow the breeze, and they might indeed make a fire less likely, Scott Stephens says. But not today. The summer fogs have faded, and it’s been unseasonably hot for a week. Relative humidity is in the low teens, and any moisture hidden in the debris below the trees has long wicked away. A strong wind begins blowing over the hills from the east. And then somehow—maybe a spark from a car, maybe a tossed cigarette—the whole dry, airy mess catches fire.

Now the flames on the ground are 30 feet high and even higher off the boughs, roaring like a jet engine. At the fire’s edges, trees appear to explode as the volatile oils in their leaves reach their boiling point and vaporize. The heat of the fire forms a convection column, with 60-mile-per-hour winds that rip burning strips of bark from the trees and toss them upward. This is another of blue gums’ talents—its bark makes ideal braziers. Tucked away inside a rolled-up strip of bark, a fire might live for close to an hour and fly 20 miles. Native species and grasses produce sparks and firebrands too, Stephens says, but not of the same quantity and quality as eucalyptus. The shower of firebrands tossed from the ridgeline by the 100-foot-tall trees foils any attempt to create a firebreak.

At this point, there’s nothing anyone can do to stop the fire, Brad Gallup says. “Nature’s going to put that out.” We’re on a ridgeline above UC Berkeley, across the street from the grove in question. I met him that morning at the park district fire station at the edge of Tilden Regional Park, and we’ve driven together into the park, stopping first at this overlook along Grizzly Peak Boulevard. Gallup, who has gray hair and thin-frame glasses, is dressed head-to-toe in navy and wears black leather fire boots. He is persistently neutral: “Everybody’s right, everybody’s wrong,” he says at one point. It is true, he says, that—as Maloney argues—a fire would spread through the grass covering the hillside on this side of the road much faster than through the eucalyptus opposite. It might indeed get away, or catch houses on fire. But even under the worst conditions, there is the possibility of containing a grass fire, he says. That’s the idea in thinning the eucalyptus—not to prevent fire, but merely to create the possibility of keeping it from growing out of control even in those rare instances when conditions are at their worst. “We’re trying to change fire behavior,” he says, “to make it easier to put the fire out, to give people more time to evacuate.”

We drive along the ridgeline and re-enter the park, and into what looks and feels like a vast eucalyptus forest. Gallup parks his truck and we get out to walk down the fire trail. We pass a man in an excavator stacking eucalyptus logs. The air begins to smell of fresh sawdust. And then from somewhere down in the woods there is the sound of a saw.

The East Bay Regional Park District is taking something of a middle approach to fire prevention in the eucalyptus groves it manages, thinning the trees rather than clearing them outright. (This is the approach that Jerry Kent predicts will cost the most, and native plant advocates say will result in a monoculture, though it is acceptable to the Hills Conservation Network.) The goal, Gallup says, is to get to less than 100 trees per acre, down from as many as 1,700 per acre in some areas. After arborists thin the smaller trees, youth crews will clean up debris and hanging bark. When the project is finished, he says, only the bigger trees will be left, with a wide gap between the forest floor and its canopy. This “shaded fuel-break,” as he calls it, should help slow down fires.

We turn a corner and stop between a feller buncher (which both fells trees and gathers them into bunches) and a chipper. The seven-boled tree is on the uphill side of the trail. From the gully below comes the whine of the saw; then it stops and a young eucalyptus topples over with a drawn-out crash. A man in a hard hat and orange vest emerges from the bushes, then cuts through another tree. The forest between us and him is already mostly thinned. The trees that remain standing are big and widely spaced. Smaller trees lie between, yet to be hauled off or chipped. Bark still hangs from trunks, awaiting the youth crews. It’s still messy, a sculpture only half done.

This is Gallup’s favorite part of the job, he says—choosing which trees to remove, which trees to keep. There is an art to it, he says. “If the plan says ‘thin eucalyptus,’ then that’s what I have to do,” he says. “But I can use my professional judgment. There’s no exact number.” When he starts a thinning project, he walks the grove and imagines how it might look without this or that tree, how the canopy would look, how it would look in a decade, in three decades. And he imagines it catching fire.

Editor’s note: In late September, FEMA rescinded its fire mitigation grants to UC Berkeley and the City of Oakland, covering the 350 most contentious acres. It did not offer an explanation. A UC press release stated that the fire hazard mitigation work in Strawberry and Claremont canyons “will be delayed for an indefinite period.”

Zach St. George is a freelance reporter based in Oakland. He writes about science and the environment, and feels that as long as we’ve got eucalyptus, we might as well get some koalas, too.

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sidney ducks on October 18th, 2016 at 4:35 pm

I think the gums are beautiful but I do can recognize that there is not much for native birds and insects to feed on and that to walk under these groves is to be in a sterile and silent cathedral. I wish we could return it to it’s natural state. And then there is the fire.

Madeline Hovland on October 18th, 2016 at 6:59 pm

You apparently did not fact-check the info about koalas and eucalyptus leaves. Koalas live and sleep in eucalyptus trees. They are NOT deterred by the oil in euc leaves. Euc leaves are the koala’s main food source. Although Ms. Rice claims that bay leaves (which have more oil in them than euc leaves) are not as ignitable as euc leaves because they have more moisture than euc leaves (this comparison is based on bias, not on facts based on scientific experimentation) there is so much water in euc leaves that koalas drink almost no other water; they get all the water they need from eating eucalyptus leaves. So, according to scientific fact (not Ms. Rice’s biased statements), euc leaves contain a great deal of moisture, as do the trunks and branches of the trees. This is one of the many reasons why euc trees do not ignite or burn easily or quickly.

I lived through the 1991 fire (and still live in the same house that did not burn in the fire although we were surrounded by fire on all sides). The fire stopped up the street at three tall eucalyptus trees, which did not ignite or burn although there were embers flying all around, dropping on wooden roofs of houses and setting them ablaze close to the eucalyptus trees.

Another point: chaparral leaves, which are smaller and more ignitable than eucalyptus leaves, also contain a great deal of oil, which causes them to seem to “explode” in fire. “When chaparral burns, it can seem like a hillside soaked in gasoline has been ignited.” (David Carle, Introduction to Fire in California, p. 38) It should be noted that Mr. Carle does not mention eucalyptus even once in this important book about fire ecology and behavior.

Victoria Schlesinger on October 19th, 2016 at 10:59 am

Hi Madeline,

Thank you for your comment. We did fact check the information about koalas and eucalyptus leaves, and the relationship between the two is not as simple as one might assume. According to the journal article “Eucalyptus foliar chemistry explains selective feeding by koalas,” Biol Lett. 2005 Mar 22; 1(1): 64–67 [https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1965198/], eucalyptus produce formylated phloroglucinol compounds (FPC), which deter koalas from eating the leaves. FPCs are complex, but researchers have found that the more a eucalyptus produces, the less a koala will eat from that tree or species. The discussion section of the study states: “The koala is an extreme example of evolutionary adaptation to plant anti-herbivore defences. Nonetheless, many eucalypts contain sufficient concentrations of FPCs to deter koalas from feeding. FPCs stimulate the emetic (nausea) system and herbivores probably learn to recognize and avoid these compounds in foliage (Lawler et al. 1999). As FPC concentrations change along ecological gradients (Moore et al. 2004b), we expect that FPCs should also affect the abundance and distribution of koalas and other folivores across the landscape.”

Mary McAllister on October 19th, 2016 at 10:23 am

“Sidney Ducks” repeats a popular myth among native plant advocates for which there is no evidence and considerable evidence to the contrary. The eucalyptus forest supports a great deal of wildlife and is essential to a few important species, such as monarchs, raptors, bees, and hummingbirds. Here are a few empirical studies that prove the eucalyptus forest is not a “sterile, silent” place.

Dov Sax (Brown University) sampled plant and animal species in eucalyptus forest in Berkeley and compared them to oak-bay woodland. This is what he found: “Species richness was nearly identical for understory plants, leaf-litter invertebrates, amphibians and birds; only rodents had significantly fewer species in eucalypt sites. Species diversity patterns…were qualitatively identical to those for species richness, except for leaf-litter invertebrates, which were significantly more diverse in eucalypt sites during the spring.” (Dov Sax, “Equal diversity in disparate species assemblages: a comparison of native and exotic woodlands in California,” Global Ecology and Biogeography, 11, 49-52, 2002.)

Robert Stebbins (UC Berkeley) inventoried vertebrates in four vegetation types in East Bay parks for the Regional Park District. This is what he found: ““Contrary to popular belief, many animals, both vertebrates and invertebrates, have adapted to life in the Eucalyptus groves. Moisture from the air condenses on the leaves and the drippage keeps the groves moist and cool even during the dry season. This is a suitable ground habitat for a wide variety of animal life…”

Igor Lacan (UC Berkeley) inventoried benthic organisms (such as gnats, mayflies, dragonflies) in streams bordered by eucalyptus compared to native trees. He found equal species diversity and populations in streams bordered by both types of vegetation. (Igor Lacan, Vincent Resh, Joe McBride, “Similar breakdown rates and benthic macroinvertebrate assemblages in native and Eucalyptus globulus leaf litter in Californian streams,” Freshwater Biology, 55, 739-752, 2010.)

A study of 180 of the over 300 sites in California used by migrating monarch butterflies found that 75% of the trees in which monarchs roost during the winter are eucalyptus. (Dennis Frey and Andrew Schaffner, “Spatial and Temporal Pattern of Monarch Overwintering Abundance in Western North America,” in The Monarch Butterfly Biology and Conservation, Cornell University Press, 2004.)

A study of nesting raptors in the Santa Clara Valley found that red shouldered hawks consistently choose eucalyptus over native trees for their nests and that when they do their nests are more successful. (Stephen Rottenborn, “Nest-Site selection and reproductive success of urban red-shouldered hawks in Central California,” J. Raptor Research, 34(1):18-25)

There are many other similar studies, but it is pointless to provide them to a publication that resists information that is not consistent with the nativist ideology.

Victoria Schlesinger on October 19th, 2016 at 11:10 am

Hi Mary,

Thanks for providing readers with additional information if they’re interested in the issue of habitat and eucalyptus. This story doesn’t go into studies such as these because as the story title suggests it’s primarily examining flammability and fire hazard and not wildlife habitat.

Mary McAllister on October 19th, 2016 at 1:36 pm

Hmmm… Yet, the article says, “Native plant advocates also argue that the trees are inhospitable to many native animals and generally reduce biodiversity…” And it quotes Jerry Kent as saying, “The native species…provide more valuable habitat.” These statements are both unchallenged and unsubstantiated by the article.

In any case, I was replying to “Sidney Ducks.”

Mary McAllister on October 20th, 2016 at 9:11 am

Ms. Schlesinger seems to have missed the point that Ms. Hovland was trying to make. I think Ms. Hovland’s main point is that there is no empirical evidence provided by the article that substantiates Carol Rice’s claim that native bay trees contain more moisture than eucalyptus does.

If there is such evidence, it should have been provided. If there is no evidence, a moisture study should be conducted to determine the relative moisture content of these two tree species.

Ms. Rice knows how to conduct such a study. Her Master’s Thesis was a moisture study of oak trees in the East Bay hills. It’s a relatively trivial test that compares the weight of the leaf on the tree with the weight of the leaf after it is dessicated for many hours in a low temperature oven designed for that purpose. The difference in the weight is the moisture content. If such a study has not been done, I invite Ms. Rice to conduct it.

Until such evidence is provided, I will assume that much like the “ignition ratings” cited by Ms. Rice, it is just another made up “fact” to support the agenda of native plant advocates who wish to destroy our urban forest.

Most of the debates around this issue could be resolved with a few scientific studies, such as ignition tests. Perhaps native plant advocates find it easier and more convenient to just make things up.

Jon Vought on October 20th, 2016 at 10:45 pm

A scientific study would confirm what is already intuitively obvious: Invasive species damage the ecosystems they invade. Period. -A Native Plant Advocate

Pam Walatka on October 21st, 2016 at 9:31 am

Thank you for well-written and well-researched article

Robert Curtis on November 9th, 2016 at 9:14 pm

A point that–to me at least–is extremely important but only occasionally mentioned is in the last sentence of the article: “…[he] imagines how…it would look in a decade, in three decades.”

The Last Word On Nothing | The Great Eucalyptus Debate on November 29th, 2016 at 1:00 am

[…] recent summary of the dispute was this feature in Bay Nature by Zach St. George. The piece seemed pretty even-handed to me, but McAllister sent […]

John Pritchard on November 29th, 2016 at 8:05 am

This is really about common sense. Dry grass is highly flammable, but a field of grass has much less fuel than a eucalyptus forest. A grass fire will burn very fast and go out very fast, while a eucalyptus forest will burn for hours. Also the plants in a grassy field are very short, so any embers will not travel very far compared to embers coming from the top of a burning eucalyptus tree. Another common sense method would be just to go out and look at trees. And person with common sense can see that eucalyptus are much more flammable than live-oaks or redwoods.

Mary McAllister on December 1st, 2016 at 6:10 am

The Million Trees blog has tracked down the origin of Bay Nature’s fantasy scenario in which eucalyptus embers travel 20 miles and start spot fires. It has compared that fantasy to the reality of actual wildfires, including the 1991 fire in the East Bay Hills. The fantasy story bears no resemblance to reality. https://milliontrees.me/2016/12/01/embers-start-spot-fires-the-real-and-the-imagined-stories/

Members of our “tree team” also found in the archives of the California Invasive Plant Council, the minutes of a workshop in 2004 in which a National Park employee advises other land managers to claim that eucalyptus is flammable in order to sell their destruction to the public. Other land managers push back, expressing their opinion that eucalyptus are not more flammable than native chaparral, which is what tree defenders have been saying for 10 years. This is the public record of the origin of the FIRE!! cover story used by nativists to sell the destruction of our urban forest.

We are living in a post-truth era in which fake news helped to install a demagogue as our president. The destruction of our urban forest pales in comparison to the consequences of the manipulation of American voters. It is merely another example of the dangers of living in a fact-free world.

Dash on December 1st, 2016 at 9:52 am

People can argue for hours and cherrypick information about flammability or native species use to suit their goals, but to me one thing that no one mentions is that with exotic species we lose our sense of place. Blue Gum grow everywhere! I recently saw huge monocultures of them in Colombia and in Chile. It’s like having Wal-mart and McDonalds, there is no local flavor, nothing to differentiate where you are. Our native plants and native ecology is what makes us unique, and I find it very sad there is this whole “anti-native” movement.

Debbie Viess on March 11th, 2017 at 8:36 am

Wow, talk about a hot button topic!

I have lived here in the BA for over 40 years. I am a naturalist, a biologist, a mycologist, a former President of a local Audubon chapter and I recently spent five weeks in the bush of eastern Australia, traipsing through many beautiful and biologically diverse eucalyptus forests.

I can say without hesitation that monoculture eucalyptus groves here in CA are a travesty of nature.
Yes, they provide shade, as do all trees. Yes, they provide perches and nest space for raptors, but so do man-made structures! As introduced species, eucalypts take more resources and grow taller. Any raptor will prefer the tallest tree. What did the monarchs do before we changed the CA landscape? Are you saying they won’t go to other trees once the eucalypts are removed?

But these are hardly intact eucalyptus forest with all of their native components of both companion plants and saprobic as well as mycorrhizal fungi, or of creatures adapted to live in a eucalyptus forest. They are trees out of place, who have managed to get a toe-hold here, through a misguided scheme to plant lumber trees. I have not read the study that you cited here, Mary, but I strongly doubt that “botanical species diversity” is the same under eucalypts vs native oak groves. I don’t consider plants like scotch broom or European grasses or vinca or Himalayan blackberry to be true species diversity. All of those plants and animals that make use of these forests are merely making do. They have to go somewhere, or they just wink out of existence.

A euc fire can’t be fought. I too lived through the Oakland Hills fire, and it was horrific. Yes, building a house in wild lands is always an iffy thing; that beauty can turn right around and bite ya! But we can’t just walk away from the folks who do live there, nor continue to support an unnatural system because b’gosh, any tree is a good tree.

No. Place is important. We discovered a lone redwood tree in a botanical garden in the Blue Mountains outside of Sydney last spring. It was as inappropriate and out of place as a euc forest in CA.

I understand that this is complicated and emotions are running high. I hate the idea of clear-cutting, and the topical application of herbicides, and yet, how does one get rid of invasives and replant natives without doing so? We can’t turn back the clock, but we can move forward in an enlightened way, and attempt to do the right thing.

A eucalyptus “forest” without true diversity is not a forest at all. Gosh, lizards will hide under any debris, and catch insects that fly by or crawl by! Does that make it a thriving ecosystem? Really? Or just the adaptation by animals who must live somewhere, when their preferred and richer habitat is gone. If you have eyes to see and a heart to feel, there is no way one could “prefer” a eucalypt grove to a native oak bay woodland.

But on the other hand, these decisions must be an open process by our local land managers: we folks who care deeply about our CA nature in all of its myriad forms will not tolerate these wild land decisions made in secret. Yes, there are many outspoken people here in the BA, and perhaps not all are science driven, and emotions color our arguments both here and across our nation, on both sides of this ecological divide. Our land managers work for us, and they must convince and acknowledge their public, recognize and allay their fears, and then, make those hard decisions and follow through.

It takes time and money and tremendous effort to positively change a forest. We human engineers can only hope to bring back what once was.

Chris on October 12th, 2017 at 5:29 am

There is a ready market for eucalyptus wood chips coming from Japan and,more than likely too,China in order to make paper and especially cardboard boxes for consumer and other products. Why not sell these noxious trees and use the funds to re-establish less fireprone ecology. Simple. Its a market driven solution providing employment as well for the forestry, nursery and plantation management folk.

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