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Butterflies of the Bay Area Region

October 3, 2014

Our readers may remember Professor Arthur Shapiro as a critic of massive ecological “restorations” that attempt to turn back the botanical clock.   Professor Shapiro is better known in the world of academic science as an expert on the butterflies of California.  His Field Guide to Butterflies of the San Francisco Bay and Sacramento Valley Regions (University of California Press, 2007) reflects a lifetime of observation and study of butterflies.  It is as informative about butterfly behavior and physiology as it is readable and engaging.  This is no dry, academic treatise.  Rather it represents an accumulation of over thirty years of experience, walking on every sunny day amongst the butterflies of California and enjoying every minute of it.

We could choose any number of interesting topics from Professor Shapiro’s guide, but we think our readers will be most interested in learning about the natural history of California and the Bay Area region and how that history resulted in our current butterfly fauna.   It’s not a gloomy story, as you might expect in a place that has changed so radically since it was occupied by Europeans in the 19th century.  Rather it’s a story of change and adaptation to change and therefore very much in tune with the concerns of the Million Trees blog.

Butterflies in the landscape created by humans

This is the reality of which plants are useful to butterflies in the Bay Area and Delta Region of California:

Red Admiral.  public domain

Red Admiral. public domain

“California butterflies, for better or worse are heavily invested in the anthropic landscape [altered by humans].  About a third of all California butterfly species have been recorded either ovipositing [laying eggs] or feeding on nonnative plants.  Roughly half of the Central Valley and inland Bay Area fauna is now using nonnative host plants heavily or even exclusively.  Our urban and suburban multivoltine [multiple generations in one year] butterfly fauna is basically dependent on ‘weeds.’  We have one species, the Gulf Fritillary that can exist here only on introduced hosts.  Perhaps the commonest urban butterfly in San Francisco and the East Bay, the Red Admiral is overwhelmingly dependent on an exotic host, pellitory.  And that’s the way it is.”

Professor Shapiro explains that alterations in our landscape made by humans made it necessary for butterflies to make the transition from natives to non-natives in order to survive:

The explanation for this odd situation can be found in the history of California’s wetlands.  As recently as the early twentieth century, there were extensive fresh water marshes in our area, especially along the east side of the Sacramento Valley.  These wetlands stayed green in the summer and could support multivoltinism because native host plants were available…The draining, diking, and agriculturalization of the wetlands corresponded in time with the widespread naturalization of exotic weeds related to native marshland plants.”

Anise Swallowtail butterfly in non-native fennel.  Courtesy urbanwildness.org

Anise Swallowtail butterfly in non-native fennel. Courtesy urbanwildness.org

Here are a few examples of native butterfly species that made the transition from native to non-native plants when the wetlands were altered by humans:

“What did our Mylitta Crescent feed on before the various pestiferous annual Mediterranean thistles come to California?  Native, mostly wetland thistles, just as it does in mountain bogs today…The Common Checkered Skipper still uses checkerbloom in wetlands where it can find it, but thanks to a weedy species of mallow it is now found in every garden and weedy lot in the northern part of the state.  And the Anise Swallowtail still lays eggs on water hemlock…in marshes, but percentage-wise very few of them.”

San Francisco is a special case for butterflies

San Franciscans know that although their city is very small in size, it is composed of many even smaller microclimates.  Professor Shapiro explains how these microclimates impacted our butterflies:

“The main reason why we have so many federally endangered or threatened butterflies in the Bay Area is that our peculiar geography is predisposed to the fragmentation of populations—particularly in the coastal fog belt.  These local evolutionary experiments may well have been dead ends in the long run…But they were so restricted to tiny chunks of habitat that even nineteenth-century development was enough to spell their doom.”

Then he reminds us what it would take to “restore” the landscapes that supported these rare or extinct butterfly species:

“Had there been an Endangered Species Act in the 1860s, San Francisco would be a very different place.  The “Great Sand Bank” occupying the western third of the city would have been declared critical habitat for any number of plants and animals found nowhere else on Earth—including three butterflies that subsequently went extinct.  We could still have the Xerces Blue, the Pheres Blue, and the Sthenele Satyr, but there would be no Golden Gate Park and no Sunset District.  The reclamation and stabilization of what was seen as a bleak, barren, fog-and-windswept wasteland were hailed at the time as triumphs of civilization.  Now some environmentalists would like to turn the clock back and restore a little of that unique habitat.  But some of its inhabitants, including those three butterflies, are gone, never to return.”

Golden Gate Park and its neighborhood.  Would you trade this for the barren sand dunes that preceded it?  Gnu Free Documentation

Golden Gate Park and its neighborhood. Would you trade this for the barren sand dunes that preceded it? Gnu Free Documentation

 However, the story isn’t entirely of loss in San Francisco:

Gulf Fritillary.  Creative Commons

Gulf Fritillary. Creative Commons

“The Cabbage White…arrived sometime in the late nineteenth century.  The Gulf Fritillary…seems to have become established only in the 1950s.  The Fiery Skipper was unknown…in 1910…Several native species treated as scarce [in 1910] have become commoner due to introduced, weedy host plants.  The Anise Swallowtail and the Red Admiral are prime examples.  The West Coast Lady, most of whose hosts are weedy, was already very abundant in [1910].”

What do butterflies need today?

Professor Shapiro provides a detailed list of the plants used by the butterflies of California.  You will find roughly equal numbers of native and non-native plants on the list of plants they like as well as the plants they don’t like.  This is how he summarizes these lists:  “Most California natives in cultivation are of no more butterfly interest than nonnatives, and most of the best butterfly flowers in our area are exotic.”

What is done cannot be undone

While humans wring their hands about “weeds” and the loss of historical landscapes, butterflies have moved on.  And so they must to survive.  And so should we because these historical landscapes cannot be recreated without abandoning the economic enterprises which feed us or the homes that house us.  We aren’t going to bull doze Golden Gate Park or the residential neighborhoods that surround it.  The least we can do for the butterflies of California is to quit dousing the plants they need with herbicides solely because they are non-native.  We have created the landscape that we need and we should quit destroying the landscape that our butterflies now need.

Professor Shapiro’s Preface is a fitting conclusion:

The changes that humans have wrought on the lives of butterflies are merely the most recent of the many changes they have gone through in their history.  We have no hope of restoring communities to some hypothetical pristine state on any but a miniature scale.  At best we create gardens that more or less resemble what we think those communities looked like at some arbitrary time in the past.  Like all gardens, they require constant effort to keep them from becoming what today’s conditions drive them to become—conditions dominated by what we characterize as “weeds.”  We can, however, try to protect the bits of nature that have survived relatively unchanged despite us, cognizant that larger forces than we control may override our efforts.”

6 Comments leave one →
  1. October 3, 2014 7:44 am

    I’m baffled as to why one third or one half of butterflies able to survive on non-native host plants would be considered encouraging news. I’d be far more concerned about the species of butterflies you might lose, which appears to be a possible majority, than pretend that is a good statistic.

    • October 3, 2014 1:33 pm

      You mistakenly assume that butterflies which do not require non-natives use exclusively natives. They do not. They use both depending upon availability.

  2. October 3, 2014 12:47 pm

    A great deal of what you folks write is quite good. I am , however, getting tired of seeing the meme that the geoforms and ecosystems that preceded European (and/or “American”) “settlement” of the Bay Area were barren or were in need of improvement by humans.
    Today’s embodiment of that attitude is displayed by the question, regarding Golden Gate Park and its surrounding neighborhoods: ” Would you trade this for the barren sand dunes that preceded it?”

    I doubt VERY seriously they were “barren”. That used to be the prevailing view of deserts, too. Be careful. On one hand, you argue that the desire of other humans than yourselves to have “native” vegetation is an impractical, naive romantic notion based on pure bias, but one the other hand one of your arguments for leaving the current state of human development, including of vegetation, is one of aesthetic preference.

    Me? Yes, I would trade it for the dunes ecosystem that preceded it. We humans have far too arrogantly and foolishly type-changed far too great a percentage of “ecosystem service” providing landscapes the world over — and it is biting us in the ass in more ways than could be counted..

    • October 3, 2014 1:11 pm

      There are many historical photographs that document that about half of San Francisco was covered by shifting, barren sand dunes. It is now the second most densely populated city in the country. It isn’t merely a question of preference. It is largely a physical reality.

  3. takebackthegreen permalink
    October 4, 2014 10:01 am

    As seems to be the norm, an expert in a relevant field makes a logical, compelling, realistic assessment of our current ecosystem, and those who seem committed to the view that humans are “the problem” (simplified but accurate characterization of that philosophy) are not even a little bit dissuaded from their misanthropy.

    To the first commentator: Nature doesn’t care or notice when a species goes extinct. The only entities that assign importance to survival are–misanthropes please note the irony– humans. Consider what Prof. Shapiro demonstrates: that Nature adapts. It is not static and we cannot make it so. It is absolutely good news that so many species happily exist in the landscape as it is. We aren’t as important as some of us like to think we are.

    To the second commentator: (this is meant in a friendly, point-making sort of way) If you think we should abandon SF in order to give it back to the Natural Paradise that existed before horrible Homo sapiens sapiens invaded and ruined it all, I say “After you, my friend! Please lead the way.” Meanwhile, I’ll be eating the delicious plums from my “exotic” plum tree and admiring the unbelievably complex web of life that thrives on the European Olive tree. I can drive a few miles down the Peninsula and see the (PRESERVED not RESTORED) beautiful, “native” rolling brown hills dotted with solitary oaks. Neither ecosystem is intrinsically more valuable or important. Nature truly does not care.

    Only certain humans.

    • October 4, 2014 12:23 pm

      Yes, misanthropic sentiment pervades nativism. Yet they aren’t volunteering for suicide. They seem to suggest we volunteer.

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