What will the East Bay Hills look like if our forests are destroyed?

If the owners of our public lands in the East Bay hills are finally successful in implementing their plans to destroy our urban forest, what will the hills look like?  The land owners tell us in their written plans that the forests will be replaced by grassland with islands of shrubs.  They also say they will preserve existing oak-bay woodlands.  However, their plans make no commitments to plant anything.  They predict that this conversion will take place naturally, without further intervention.

The Sierra Club, which advocates for the destruction of our urban forest, is more specific about their desire for a native landscape.  The Sierra Club says, “Existing native plants in the understory will be preserved and replaced naturally. Grass and shrub land will be restored…with more naturally fire-resistant native trees and plants.”

Are these realistic predictions for the future of the East Bay hills if most of the non-native forests are destroyed?  That’s the question we will ponder today.

Grassland in California

We predict that grassland is the likely immediate outcome of tree removals.  The grassland will quickly succeed to shrubs in the absence of grazing and periodic fires.  However, that grassland won’t be native because grassland in California has not been native for over 150 years.  Here are a few of the sources of that information:

  • “…only about 1% of [California] grassland today could be considered pristine [AKA native]” (1)
  • “Non-native species are widespread and often the dominant plants in California’s grasslands…it is clear that annual grasses…are dominant over enormous portions of the state.” (2)
  • David Amme is one of the co-founders of The California Native Grass Association and one of the authors of East Bay Regional Park District’s “Wildfire Hazard Reduction and Resource Management Plan” at a time when he was employed by EBRPD. In an article he wrote for Bay Nature he lists a few small remnants of native grasses in the East Bay and advises those who attempt to find them, “As you go searching for these native grasses, you’ll see firsthand that the introduction of the Mediterranean annual grasses is the juggernaut that has forever changed the balance and composition of our grasslands.” (3)
  • In a video recording of a lecture given to ecology students at UC Berkeley, Professor Joe McBride tells the students that an inventory of grassland in Strawberry Canyon found that it is 97% non-native annual grasses. (4)
Trees were destroyed here by UC Berkeley over 10 years ago. The landscape is now non-native annual grasses. This is the typical outcome of tree removals on sunny hills without a water source.
Trees were destroyed here by UC Berkeley over 10 years ago. The landscape is now non-native annual grasses. This is the typical outcome of tree removals on sunny hills without a water source.
Poison hemlock and thistle are 8 feet tall where not sprayed with herbicide. Site 29, May2016.
Along the roads and riparian corridors, where trees have been destroyed, tall weeds reign.  Poison hemlock and thistle are 8 feet tall where not sprayed with herbicide. Site 29, May 2016.

Why were native perennial bunchgrasses quickly replaced by non-native annual grasses?

David Amme explains why non-native annual grasses quickly replaced native bunch grasses in his article in Bay Nature: 

“The Mediterranean annual grasses grow faster and bigger than the native bunchgrasses. Established annual grass stands produce ten times the amount of seed as do native grass stands of equal area, and most important, their seeds are five to ten times larger, giving them a big jump on establishment and fast growth. Another advantage they have is their shallow, weblike root system, which quickly exploits the moisture near the surface of the soil, rendering tiny, slow-growing native perennial seedlings helpless.(3)

Serpentine Prairie being weeded by hand. Mowing will be required during the restoration. Prescribed burns will be required to maintain it as prairie.
Serpentine Prairie on Skyline Blvd is one of the small remnants of native bunch grasses in the East Bay.  Serpentine soil suppresses the growth of annual grasses.  About 8 years ago 500 trees (including many oaks) were destroyed there to begin a restoration attempt.  It is being weeded by hand. Mowing will be required during the restoration. Prescribed burns will be required to maintain it as prairie.

Stromberg says land use changes were also instrumental in the replacement of native grasses by non-native annual grasses:

“…drought, combined with intensification of crop agriculture and intensive year-round livestock grazing resulted in a dramatic decline in native perennial grasses over a relatively short period.  Diaries of early explorers such as John Muir also suggest that dramatic change occurred relatively rapidly in the mid 1800s.  Native species were presumably replaced with non-native annuals whose seeds had become widespread as a result of transport by livestock, contaminations of seed crops, or active planting as forage crops.”  (2)

European annual grasses evolved with a 40,000 year history of association with human disturbance in Eurasia and are therefore pre-adapted to take advantage of a highly disturbed environment such as agricultural and urban environments.  They are also much more drought tolerant than California native grassland.  (2)

Another factor in the dominance of non-native annual grassland is that many are known to be capable of transferring atmospheric nitrogen into the soil (called “nitrogen-fixers”). Modern burning of fossil fuels has increased atmospheric nitrogen levels.  These two factors combine to increase levels of nitrogen in the soil.  High levels of nitrogen in the soil “promotes fast-growing exotic annual grasses to the exclusion of native species.”  (2)

What are the prospects of restoring native bunch grasses in the Bay Area?

Given the competitive advantages of non-native annual grasses, is it realistic to expect native bunch grasses to “naturally” colonize the landscape when the forests are destroyed without being planted?  Probably not.

Stromberg reports on 18 grassland restoration projects on 943 acres in California in California GrasslandsAll eighteen of those projects planted native plants after using various methods to eradicate non-native annual grasses.  78% of the projects used herbicides.  61% of the projects also used grazing.  56% of the projects also used some combination of mowing, disking, or burning.  11% of the projects also irrigated.  None of these projects resulted in exclusively native grassland and none predicted permanent return of native grassland.  (2)

Dunnigan Test Plot, August 2011. The result of an eight-year effort to restore native grassland. Does it look "biodiverse?" ecoseed.com.
Dunnigan Test Plot, August 2011. The result of an eight-year effort to restore native grassland. Does it look “biodiverse?” Courtesy ecoseed.com.

We reported on a project in which nearly $500,000 was spent to convert 2 acres of non-native annual grasses to native grasses over a period of 8 years.  Every possible combination of planting and eradication was used.  When they ran out of money, they described their success as 50% native grasses that were predicted to last for 10 years.

We turn to David Amme again to describe the prospects of converting non-native to native grassland:

“…the Mediterranean annual grasses are a permanent part of the Californian grasslands, and they now are as much a part of California’s grasslands as the native perennial grasses once were. The time is long overdue for an official naturalization ceremony. Despite the losses suffered by native plants in the face of exotic grasses, the East Bay annual grasslands remain a tremendously productive ecosystem, in terms of producing great volumes of both forage and seed.”  (3)

And apparently East Bay Regional Park District agrees with that assessment, judging by this sign posted at Inspiration Point in Tilden Park:

Sign at Inspiration Point, Tilden Park:
Sign at Inspiration Point, Tilden Park:  “By the 1860s [native grasslands] were largely replaced by Mediterranean grasses –‘supercompetitors’ that can be managed by grazing or burning, but never eliminated.”

 And the future of grassland is bleak

Researchers at Stanford University conducted a study of the future of grasslands in California by mimicking carbon dioxide and temperature levels that are predicted in the future: “In the course of a 17-year experiment on more than 1 million plants, scientists put future global warming to a real-world test.”

Here is what they learned: “The results aren’t pretty…the plants…didn’t grow more or get greener. They also didn’t remove the pollution and store more of it in the soil…Plant growth tended to decline with rising temperature….grassland ecosystems will likely not be able to tolerate the higher temperatures and increased drought stress.” (5)

Bay Nature published an interview with Elizabeth Hadly, Stanford University Paleoecologist and recently appointed faculty director of Stanford’s Jasper Ridge Ecological Reserve, where that research study was conducted.  Professor Hadly told Bay Nature, Global change is in motion and there is no going back, no ‘restoration’ to some historic state.  I want to anticipate the future.  How do we anticipate the future of the nature reserve in this place?”  (6)

We agree with Professor Hadly.  In a rapidly changing climate, conservation efforts should look to the future, not to the past.  The past is increasingly irrelevant to conservation.

Ignorance or Strategy?

Why does the Sierra Club believe that our urban forests will be replaced by native grassland?  Are they ignorant of the fact that our grassland is almost entirely non-native annual grassland?  Are they unaware of the fact that none of the owners of our public land in the East Bay has any intention to plant native plants?  Are they unaware of the competitive advantages of non-native grasses and the notorious failures of attempts to convert grassland from non-native to native?

Or is their ignorance actually a strategy?  Do they want to seduce their followers into believing that destroying non-native trees will result in the return of a native landscape?

We don’t claim to know the motivation of those who demand the destruction of our urban forest.  But we know this:  destroying our urban forest will not magically produce a native landscape.  Claims that it will are either dishonest or delusional.

In our next post we will address the claim that oak woodlands will also expand as a result of destroying our non-native forests.  Preview:  the claim that oak woodlands will expand is also delusional.

  1. Alan Schoenherr, A Natural History of California, UC Press, 1992, page 520
  2. Mark Stromberg, et. al., California Grasslands, UC Press, 2007, page 67
  3. David Amme, “Grassland Heritage,” Bay Nature, April 1, 2004
  4. https://youtu.be/aBnvjDFT6X0
  5. http://www.dailymail.co.uk/sciencetech/article-3774958/Future-climate-change-field-test-doesnt-make-Earth-greener.html
  6. “Elizabeth Hadly Turns to the Future,” Bay Nature, October-December 2016