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Sudden Oak Death

August 21, 2010

Coast live oak, Mountain View Cemetery, Oakland

The coast live oak that is native to the Bay Area is one of our favorite trees and we would be happy to see more of them.  However, the epidemic of Sudden Oak Death that is killing oaks in California and Oregon makes us question the wisdom of replacing non-native trees with oaks that may not survive that epidemic.  Since any dead tree is more flammable than any living tree, we are also skeptical about claims that restoration of the oak-studded grassland will reduce fire hazard in the Bay Area.

Sudden Oak Death, US Forest Service photo

 The pathogen (Phytophthora ramorum) that causes Sudden Oak Death (SOD) was reported  on the UC Berkeley campus in 2002.  At that time it also existed at the UC Botanical Garden and the researcher who identified the pathogen speculated that it probably existed throughout the East Bay.  By 2008, the SF Chronicle reported   that the infestation of SOD existed in several parks in the East Bay.  The researcher estimated that about 20% of all coast live oaks in the East Bay are infected with the pathogen that will eventually kill them.

In February 2008, the California Oak Mortality Task Force estimated  that ”millions of tanoak and coast live oak” have been killed by SOD in California.  Thirty four other species of trees and shrubs are also infected with the pathogen, including bay laurels and redwoods.  Although these species are not usually killed by the pathogen they are vectors of the disease.  The bay laurel is singled out by the scientific literature as being particularly effective at transmitting the pathogen to the oaks that are then killed.

The “Wildfire Hazard Reduction and Resource Management Plan” of the East Bay Regional Park District proposes to destroy most non-native trees on over 1,500 acres of parkland.  The “vegetation management goal” for most of these acres is the restoration of “oak-bay woodland.”  And so we ask these rhetorical questions:

  • What is the probability that coast live oak will survive the deadly SOD pathogen in the Bay Area?
  • Does the proximity of bay laurel to the local oak population increase the probability of infection?
  • If the oaks are killed by SOD will the risk of wildfire in the East Bay hills increase?
  • If the non-native trees are destroyed and the oaks are killed by SOD will the resulting landscape be entirely treeless?

We believe these are legitimate questions and when we have asked them of native plant advocates we have not heard an adequate answer.  We believe that eradicating non-native plants and trees without a clear understanding of the future of the natives, is irresponsible.

3 Comments leave one →
  1. August 21, 2010 6:48 pm

    That’s a really interesting post.

  2. avidhiker permalink
    August 22, 2010 9:16 am

    So I’m confused. Does the EBRPD plan call for planting coast live oak specifically or does it just state “Oak” ? There are many species of oak trees in the east bay parks. Coast live oak is the species most susceptible to SOD. How do valley oak, black oak, oak, palmer oak fare against the disease? How about the other species of live oak? Canyon and interior? What types of non-native trees is the park district proposing to remove? Eucalyptus?

    • August 22, 2010 11:18 am

      According to the US Forest Service, SOD kills other species of oak as well (“,,,tanoak (Lithocarpus densiflorus), coast live oak (Quercus agrifolia), California black oak (Quercus kelloggii), Shreve oak (Quercus parvula var. shrevei), and madrone (Arbutus menziesii) have been killed by a newly identified species, Phytophthora ramorum, which causes Sudden Oak Death.” 2002 http://www.na.fs.fed.us/spfo/pubs/pest_al/sodwest/sodwest.htm

      The “Wildfire Plan” (http://www.ebparks.org/stewardship/fireplan/ ) of the East Bay Regional Park District defines “oak-bay woodlands” on page 186 of the plan: “The canopy of oak-bay woodland communities is composed of coast live oak, California bay, and madrone trees…” Although there are other species of oaks in the East Bay, the coast live oak is the predominant species of oak.

      The plan proposes to remove most eucalypts from over 1,350 acres, all Monterey pines from 144 acres, all acacia from acres that are not quantified by the plan, as well as unquantified acres of non-native shrubs such as broom.

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