Eucalyptus: Beauty or Beast?
Restoration pits these exotics against California natives. But for some, they’re a natural.
On a Saturday morning in early September, the Sweet Springs Nature Preserve in Los Osos, Calif., bustles with activity. To the east, a dozen or so volunteers struggle to stem the tide of veldt grass that laps at the feet of waist-high lupines. To the west, a great egret stalks the shallows of a small pond, and a few dog-walkers meander along a trail shaded by a lacy canopy of towering Tasmanian blue gums, a type of eucalyptus tree.
Invisible but no less real is the cultural fault line that runs through this preserve, which is managed by the Morro Coast Audubon Society. On one side stand those who would remove some of the blue gums to restore an embattled native ecosystem; on the other are those who believe these tall exotic trees have as much right to exist as the indigenous redwoods, California's official state tree.
As environmental clashes go, this one seems fairly minor, even inconsequential. At issue is the fate of perhaps a hundred blue gums out of the more than 450 that presently grow on the 32-acre preserve, whose springs feed the Morro Bay estuary. Yet the dispute affords insight into a much wider conflict that affects the entire California coast, one that springs from different visions of the natural world and the place of non-native species in it.
Strikingly, the combatants on both sides consider themselves environmentalists, so that beneath the fraught rhetoric lie concerns that are not easy to dismiss. Both seem to share a passionate love for nature, but disagree about which organisms deserve priority. The raptors that sometimes nest in the blue gums and the monarch butterflies that use them for winter shelter? Or the Morro blue butterfly and the myriad less charismatic creatures that thrive amid native grasses and wildflowers?
The trees are problematic for a number of reasons. They grow so fast that their branch structure often gets out of whack; left unmanaged, they tend to lose large limbs, posing a danger to people and property. They drop so much bark and leaf litter and commandeer so much water and light that only the most robust, shade-tolerant natives can grow alongside them. Blue gums can also be invasive. Given access to year-round moisture, they readily spread beyond where they were originally planted. At Sweet Springs, preserve manager Holly Sletteland regularly pulls out the blue gum "volunteers" that sprout amid native shrubs and perennials.
And that's not all. Eucalyptus stands can pose a serious fire danger, as became apparent in 1991 when blue gums burst into flames that lit up the Oakland Hills. While these non-native trees hardly bear all the blame – tinder-dry grasslands, native scrub and Monterey pines also contributed to the firestorm – the fuel load provided by eucalyptus debris unquestionably intensified the blaze. In the span of 72 hours, 25 people died, and well over 3,000 houses and apartments were destroyed.
Yet these same trees, with their shaggy bark and spicy fragrance, are beloved by many. In the blue gum's immigrant history, people see an experience that parallels their own, observes environmental historian Jared Farmer, author of Trees in Paradise: A California History. "There are still a significant number of Californians who are the first generation in the state. They have come to love California. They have come to think of it as home. And they feel this kinship with the eucalyptus. They say to themselves, 'This tree is not from here, but it's beautiful, and it seems to fit.' "
But just where in 21st century California do blue gums belong, I wonder as I stroll through the Sweet Springs Preserve. How should the managers of private and public lands balance their positives and negatives? How, for that matter, can Californians weigh the value of shade and scent and high-rise drama against that of reassembling ecological communities that could serve as Noah's arks for increasingly rare native species?
The eucalyptus genus embraces upwards of 700 species, which range in size from multi-stemmed bushes to trees that approach 300 feet, making them the tallest flowering plants in the world. Eucalyptus globulus, the Tasmanian blue gum, along with Eucalyptus diversicolor, the karri tree, and Eucalyptus regnans, the mountain ash, rank among the latter. In the world of trees, only California's coastal redwoods grow taller.
European explorers first took note of these singular trees, with sticky resin or "gum" oozing from their bark, in the 17th century. Then, in 1792, when a French expedition landed in Tasmania, botanist Jacques-Julien Labillardière noticed a tall blue gum in bloom and had it felled in order to collect its flowers. Little more than a half-century later, eucalyptus seedlings, Tasmanian blue gums among them, were being offered for sale by nurseries in San Francisco and Oakland and planted, often en masse, as windbreaks, as wood sources, as aesthetic enhancements.
Among those who displayed an early interest in the trees was wilderness advocate John Muir, cofounder of the Sierra Club. In 1889, he planted a gum tree on a friend's estate in South Pasadena. Some 15 years later, Muir spent four months traveling through Australia and New Zealand, reveling in his walks through "the heart of the forest primeval, where trees are tallest and least changed by man." Today, a statuesque manna gum, one of the blue gum's many relatives, stands watch over Muir's gravesite in Martinez, Calif.
Not until the 1980s did the generally positive attitude towards eucalyptus trees begin to erode. It was then, says historian Farmer, that conservation biologists began voicing alarm about the impacts of invasive species on native ecosystems. (In California, at least, "native" has a strict definition: It means the trees, shrubs and flowering plants that existed here before 1769, the year Father Junipero Serra crossed the Tijuana River.) From the scientific literature, the concern spread, and soon terms like "non-native" and "invasive" entered the rough-and-tumble of public debate.
Starting in the 1990s, shortly after the Oakland Hills fire, prominent parks in the coastal region began removing significant numbers of blue gums, as did other public and private institutions. The process has continued, often driven by risk assessment – the danger posed by fire and falling limbs from unmanaged eucalyptus stands. Other times, it's inspired by the encroachment of the trees on habitat deemed critical to native plants. At Sweet Springs, for example, the area at the center of the controversy retains small populations of the rare Blochman's leafy daisy and the federally endangered Morro shoulderband snail.
In response, pro-eucalyptus activists have packed public meetings and established websites to protest what they view as a broad, at times conspiratorial, attack on beloved trees by those they disparage as "nativists." Last year, the Morro Coast Audubon Society was so stunned by the outcry when it filed for a county permit to remove some of the Sweet Springs blue gums that it put the project on hold. In San Francisco, some 240 miles north of Los Osos, eucalyptus fans are currently battling the city's Department of Recreation and Parks over plans to reduce the number of blue gums in areas it manages. They have also protested the University of California, San Francisco, which in August began thinning blue gum stands on 900-plus-foot-tall Mount Sutro, one of the city's highest points.
The opposition has become increasingly sophisticated, with eucalyptus fans scouring the scientific literature to find articles that bolster their position. Among the prime exhibits is a controversial essay by Macalester College ecologist Mark Davis and 18 other scientists, which calls into question the danger posed by many non-natives and the utility of fighting them on a broad landscape scale.
At its core, though, the pro-eucalyptus position draws its strength not from science but from a deep reverence for trees. "Eucalyptus trees, oak trees, redwood trees, they're all trees, and trees are good," says Los Osos resident Joey Racano, a musician, artist and environmental activist who lives less than two miles from the Sweet Springs Preserve. "Trees make things cooler. They support life. They provide places where birds can hide." Why should it matter that blue gums trace their origins to distant shores? "They are now part of our ecosystem and causing us to redefine the word 'native.' "
Seeking clarity on the subject, I visit Matt Ritter at California Polytechnic State University in San Luis Obispo, some 12 miles east of the Sweet Springs Preserve. A professor of botany, Ritter is also the director of the Cal Poly Plant Conservatory, chair of the city's Tree Committee and author of A Californian's Guide to the Trees Among Us. Many of the state's eucalyptus stands, he says, were planted in the early part of the 20th century during a short-lived commercial craze. Fast-growing and drought-tolerant, the tall trees seemed like the solution to the "wood drought" then plaguing the West. If all went according to plan, blue gums and other species would provide lumber for houses, piers, railways and fences, not to mention tannin, fiber and fuel.
As building material, however, the young wood proved disappointing, and many plantations were abandoned. Near Los Osos, a major speculator was Alexander S. Hazard, who farmed and ran a dairy in San Luis Obispo County. In 1965, his former property, with its rows upon rows of eucalyptus, became part of Montaña de Oro State Park. The Sweet Springs Preserve was once part of a cypress plantation that evidently grew blue gums as well. "In many ways, what we're dealing with today is the legacy of an unharvested crop," Ritter says.
Ritter is one of the few scientists who have seriously studied eucalyptus invasiveness in California. Of more than 200 species of eucalyptus that presently grow in the state, he and a colleague reported in 2009, only 38 are widespread. Of those, only 18 species have reproduced enough to become naturalized, and, of those 18, only two –– blue gums and red gums –– can be considered even moderately invasive, and then only in places refreshed by perennial moisture in the form of streams, springs or summer fog.
On the computer screen in his office, Ritter pulls up a series of aerial photographs that illustrate the expansion of a former blue gum plantation, 150 miles north of us. "Here's a photo that was taken in 1931," he says. "Here's what it looked like in 2001." The outward march has occurred at the rate of about two feet a year, he calculates. "And over the course of seven decades, that will take you somewhere." At the same time, two feet a year comes nowhere near the expansion rate of, say, veldt grass, an import from Southern Africa whose featherweight seeds ride the winds to distant locations.
Even more interesting to Ritter are the 16 eucalyptus species that, so far, have shown no inclination to spread. Among these is the karri tree, or Eucalyptus diversicolor, which rivals the blue gum in size. What if karris had been planted instead of blue gums? Would that have defused the eucalyptus problem? "It would remove invasiveness as an issue," Ritter replies, but the other complications, such as the hazards the big trees can pose and their competition with natives for light and water, would remain.
I ask Ritter about Sweet Springs. He hates to see big trees taken down, he says. But at the same time, he supports well-designed native plant restorations and considers Audubon's Sweet Springs plan to be one. "If you remove some of the eucalyptus and plant 10 to 15 species of native plants in their place," he says, "you should end up with a more stable and diverse ecosystem."
Back at Sweet Springs, I walk from the central part of the preserve, with its towering eucalyptus, to Sweet Springs East, the eight-acre tract that Audubon acquired in 2008. Slightly under half of it consists of wetlands, including a luxuriant salt marsh that borders the Morro Bay estuary. Higher up is an open expanse, now covered in veldt grass, which used to be native dune scrubland. This is the core of the area the Audubon Society wants to restore.
Ripping into the veldt grass, shovel in hand, is David Chipping, a retired Cal Poly geologist who is also president of the local chapter of the California Native Plant Society. He points to a row of blue gums along the boundary with the main preserve. "Audubon's idea was to target the trees along the edge of the wash there," he says. "You can't see it now, but wintertime, those eucs plunge almost all of this into shade, when, for these natives, it's meant to be sun all around." The blue gums hamper restoration in other ways as well, smothering plants with bark and leaf litter. They also reseed themselves and require regular weeding.
Around two dozen of the roughly 120 blue gums here are still small enough to be removed without a permit. The others fall into a different category. Some look to be almost 100 feet tall, with trunks as sturdy as the columns of a courthouse and outer bark that peels away to reveal a multi-hued inner layer. Many people like them, Chipping acknowledges. Nor do they lack ecological value. Consultants hired by the Morro Coast Audubon Society have confirmed that monarch butterflies and raptors, including great horned owls and red-shouldered hawks, make at least occasional use of the blue gums in Sweet Springs East.
No wonder that people who agree about other issues, such as the importance of open space, disagree so sharply where blue gums are concerned. "It's simply different values, and it's hard to say what's absolutely right and what's absolutely wrong," Chipping says. "I'm so worried about the species we're destroying that I'm on one side here. I'd just like to see a native ecosystem at Sweet Springs that is relatively intact and that helps support pollinators like the Morro blue butterfly and all the other animals that might otherwise disappear."
At the end of the day, after Chipping and the other volunteers have left, the veldt grass they've pulled sits stashed in bags, awaiting composting. To the west, the contested line of blue gums reaches for the sky. A football field away, hundreds of newly planted natives – mock heather, dune buckwheat, sand verbena, California croton – are starting to settle in.
In November, a couple of months after visiting Sweet Springs, I learn that the Morro Coast Audubon Society board backpedaled on its plan to remove blue gums. While approving the removal of small trees – those with trunk diameters of eight inches or less – it took the larger trees off the table. Flagged as exceptions to be considered on a case-by-case basis were trees that pose risks to life or property. Otherwise, the board left open the possibility of pursuing a broader tree removal at some later date, assuming sufficient "money, patience and time." For now, it seems, an uneasy truce prevails between the blue gums, the natives and the people fighting passionately for the future of them both.