Given the very serious drought conditions facing California, combined with longer and more serious wildfire seasons due to climate disruption, it’s more important than ever to prioritize fire prevention in our vegetation management strategies for the East Bay hills. For decades, the Sierra Club has worked closely with fire experts, public officials, fire fighters, and fellow environmental groups like the Audubon Society, the California Native Plant Society, and the Claremont Conservancy to design an ecologically- and fiscally-sustainable model for fire management that not only reduces the risk of fires, but also promotes diverse and healthy ecosystems. This strategy entails removing flammable, ember-generating species like eucalyptus in phases — and only in select areas considered most at risk for fire along the urban-wild interface — so that less flammable natives can reclaim those areas and allow a rebound of biodiversity.
The Sierra Club’s program for vegetation management can summarized as the “Three R’s”:
- Remove the most flammable non-native plant species in select areas considered most at risk for fire along the urban-wild interface of the East Bay hills;
- Restore those areas with more naturally fire-resistant native trees like bays, oaks, laurels, and native grasslands; and
- Re-establish greater biodiversity of flora and fauna, including endangered species like the Alameda whipsnake.
There is a lot of misinformation floating around about this preferred strategy for the care and management of vegetation in the East Bay hills. We hope this document can help correct these misunderstandings and help build support for an approach that would reduce fire risk, encourage healthy ecosystems, and reduce the financial burden on taxpayers.
How did non-natives like eucalyptus get here in the first place?
Non-native eucalyptus trees were introduced to the East Bay hills in the late 1800s by two Oakland businessmen who forested the hills with eucalyptus plantations for hardwood lumber production. The brittle wood proved unsuitable for lumber, however, and the plantations were abandoned and allowed to spread throughout the hills, overwhelming native species and changing the nature of the ecosystem. The result is groves of highly flammable invasives, which can become densely packed at 400 to 900 trees per acre, and can exceed 120 feet in height, with a tendency to dramatically explode when on fire.
What covered the hills before these non-natives were introduced?
Before the introduction of non-natives like eucalyptus and Monterey pines, the East Bay hills were a mix of chaparral grasslands and riparian vegetation along streams. Native plants adapted to the local climate over millennia to be drought tolerant and low consumers of water. Natives are also naturally more fire resistant.
Are eucalyptus and Monterey pines a greater hazard than native vegetation?
Yes! Eucalyptus and Monterey pines can leave up to 50 tons of flammable fuel on the ground per acre, as well as deep duff and dense eucalyptus- and pine-seedling growth within and around the grove. This compares with one to five tons of fuel per acre in grasslands, native live oak groves, and bay forest. A study conducted by the US Forest Service found that a mature eucalyptus forest in the Berkeley hills contains 8.23 tons per acre of litter while an oak-bay woodland contains a mere 1.71 tons per acre.
Eucalyptus branches, leaves, and bark slough off in long pieces that end up draped on one another, creating a near-optimal mixture of oxygen and fuel. The smooth, aerodynamic bark provides a way for fire to climb into the tree canopy and send burning material aloft. Dead debris can also become suspended between branches, creating a nearly continuous arrangement of fuels — horizontally and vertically.
In Australia, eucalyptus trees are sometimes referred to as “gasoline trees” for their tendency to quickly spread explosive fires. Eucalyptus leaves contain enough oil that it is sold as a product in some countries. The leaves have three times the energy of cellulose, so they burn hotter. Blue gum eucalyptus leaves release volatile chemical gases at relatively low temperatures and ignite easily.
What happens when a eucalyptus catches on fire?
Groves of eucalyptus trees create fuel ladders that spread rapidly into the canopy. When wind-driven wildfire reaches eucalyptus tree crowns, it can spur flames that reach over 150 feet into the air, with burning embers blowing downwind beyond a half mile. Eucalyptus embers also stay lit longer than embers from other vegetation. In contrast, native plants generally grow below 40 feet in height and are more easily controlled in the case of a wildfire.
Do climate disruption and changing weather patterns contribute to fire risk?
Yes. Unfortunately, climate disruption means that the conditions that lead to wildfires are much more common. Temperatures are rising and we’re getting less rain, which means that wildfires are more frequent and more damaging, and wildfire season is longer.
Why can’t we just thin the eucalyptus and other non-natives?
While thinning the eucalyptus and Monterey pine plantations seems like an appealing compromise, in reality it compounds the problem. Thinning actually denudes hillsides to an even greater extent than removing them altogether, because in order to keep the hills fire safe, it requires regular, wholesale clearing of the understory and hanging debris — including native vegetation. This has to happen on an ongoing basis for the life of the remaining eucalyptus. Then, as trees die, they must be cut down and removed to prevent accidents. Thinning means that the hills will end up being a monoculture with a bare understory — a situation that will not support diverse ecosystems including endangered species.
Won’t removing the non-natives leave a barren landscape?
Quite the opposite. Hidden among the eucalyptus and Monterey pine plantations are native oaks, bays, and willows that are struggling to survive under the canopy. These native species cannot grow to full size beneath the canopy of eucalyptus and Monterey pines.
Oaks, bays, and other native trees present under eucalyptus or pine canopies should be saved during non-native removal. Once non-natives are removed, the natives can get the sunlight and water they need to grow and thrive.
Will every eucalyptus in the East Bay hills be removed?
Not at all. Only the eucalyptus in the areas most at-risk for fire and at the urban-wild interface would be removed. Thousands of acres of eucalyptus would remain under this model for vegetation management.
Has the restoration of native landscape been done successfully in our hills?
Yes! When the eucalyptus trees on the south side of Claremont Avenue were removed by the University of California, Berkeley and the Claremont Canyon Conservancy, it did not take long for the native trees and shrubs to flourish and become a beautiful native landscape. Drive up Claremont Avenue to Signpost 29. To the right, looking south, is the restored native landscape that was once a eucalyptus forest. Turn and face the opposite direction and you will see the dense forest of eucalyptus suckers that sprouted after the 1972 freeze. Look closer and you will find native bays, oaks, and willows hidden in the eucalyptus shadows.
How do you prevent the eucalyptus from growing back?
Unfortunately, simply cutting down the eucalyptus trees doesn’t solve the problem. Unless the stumps are disabled, multiple stems or “suckers” will quickly sprout, producing several new trees where only one existed previously. There are various methods to prevent eucalyptus stumps from sprouting. The Sierra Club expects agencies to have protocols for handling herbicides and does not endorse any particular method, but understands that the costs and benefits of all options must be weighed in order to find a sustainable and fiscally responsible approach.
In some cases, the agency that manages the land will choose to apply an herbicide like Garlon to the eucalyptus stumps to prevent regrowth. In those cases, the herbicide is applied by hand to freshly cut stumps. Garlon is similar to store brand treatments sold to the public and has been approved by independent experts. The product has been deemed safe for use in all planned application settings and around natural environments.
What happens to the eucalyptus and pine trees once they are felled?
The tree trunks and branches are ground into chips. The chips themselves decompose and disintegrate rapidly. Fire professionals agree that they do not impose anywhere near the fire hazard of the standing trees.
How does this approach measure up in terms of costs?
The approach endorsed by the Sierra Club and other environmental groups is the most cost-effective strategy in the long term. Merely thinning the non-native trees would burden taxpayers with hundreds of millions of dollars in future maintenance costs. Over a period of 20 to 40 years, the costs of regular thinning of non-natives and debris removal can be conservatively estimated at around $250 million. These long-term costs would force agencies like the City of Oakland and the East Bay Regional Park District to levy fire-maintenance taxes as high as $200 per household in the East Bay — or else defer maintenance and risk a deadly and destructive fire. On the other hand, once established, native plant communities are much cheaper to maintain.
Remember that wildfires are incredibly expensive, both in terms of lives and money. The 1991 East Bay hills fire destroyed over 3,450 homes, killed 25 people, and injured 150 others. The National Oceanic and Atmospheric Administration estimates that the fire cost $3.9 billion in present-day dollars. Given these stakes, it’s critical to employ the most effective fire-management strategy, and that entails the removal of the highly flammable non-natives.
What about wildlife and endangered species?
The restoration of native vegetation creates healthier ecosystems and promotes greater biodiversity. As the California Native Plant Society wrote in its letter of support for the Sierra Club’s position on fuels management in the East Bay hills, “We recognize the importance of native plant communities and native plant habitats, in the intricate and complex web of life that is our natural world. Our locally evolved flora supports a rich palette of interconnected life, from the insect world to birds, amphibians and reptiles, mammals, fungi, etc.”
Restoration of native vegetation also provides an opportunity for the return of endangered species like the Alameda whipsnake. The U.S. Fish and Wildlife Service biological opinion calls for the restoration of whipsnake habitat through the removal of the eucalyptus and restoration of native habitat. Eucalyptus and pine groves, even thinned, do not provide habitat for the endangered whipsnake, and the East Bay hills provide prime habitat areas for this endangered species — but only if the invasive non-natives are removed.
Have more questions?
Don’t hesitate to reach out! Call the Sierra Club San Francisco Bay Chapter office at 510-848-0800 or firstname.lastname@example.org.