Three Myths About the Monarch Butterfly

The beautiful Monarch butterfly – possibly America’s best-known butterfly – is being considered for “endangered”status under the Endangered Species Act. Meanwhile, we’re cutting down the trees these creatures depend on. Nativist myths are partly responsible.

There are two migrations of these butterflies: East of the Rockies, these butterflies migrate between Mexico and the northern part of America. On the Western side, they migrate between the interior and the coast. These are the butterflies we see in California.

The Eastern migration is threatened mainly by a lack of milkweed, their nursery plant, as farmers efficiently exterminate the “weed.” But the Western migration is threatened by something different – a steady reduction in wintering sites as the war on eucalyptus trees continues. On Treasure Island, where Monarchs have been known to over-winter in some years, hundreds if not thousands of trees are being cut down.

We think the article  below is an important one. It’s  republished with permission from “Death of a Million Trees.” Recognizing the truth will help us save these beautiful creatures.

MONARCH MYTHS REVISITED by Million Trees

Debunking the myths of nativism—especially those that justify the eradication of non-native trees—is the task we have assigned ourselves, which requires us to revisit a few of the misconceptions about monarch butterflies in California.

Monarch Butterfly. Creative Commons

Monarch Butterfly. Creative Commons

When application for endangered status for monarchs was filed in August 2014, a few new monarch myths emerged and have since been faithfully repeated by native plant advocates who are demanding the eradication of our urban forests.  The monarch migration in California is using predominantly non-native trees, which should afford those trees some protection.  Unfortunately, it has only produced more convoluted theories that deny the value of non-native plants and trees to monarchs.

Myth #1:  The California migration of monarch butterflies prefers native trees for their winter roost. 

Monarch butterflies roosting in eucalyptus tree.

Monarch butterflies roosting in eucalyptus tree.

A study of the trees used by monarch butterflies for their winter roost in over 300 different sites in California reported that the vast majority of monarchs are using eucalyptus:

“Three types of trees were used most frequently by roosting monarchs:  eucalyptus (75% of the habitats primarily Eucalyptus globulus), pine (20% of the habitats; primarily Pinus radiata), and cypress (16% of the Cupressus macrocarpa).  Twelve other tree species were identified…with a combined prevalence of only 10%.” (1)

Unfortunately, this fact has been obscured by a small study of a few selected sites used by monarchs during their migration.  Griffiths and Villanova (2) observed the monarch migration in a few sites in Monterey and San Luis Obispo counties.  They report that the monarchs moved around among three tree species including eucalyptus, suggesting to them that Monterey pine and cypress are equally important to the monarchs.  While we don’t doubt that this may be true, we don’t think we can generalize from this study because it was conducted in the small native range of Monterey pine and cypress.

The California migration of monarchs spends the winter months roosting in tall trees in 17 counties along the coast of California, from Mendocino County in the north to San Diego County in the south. (1) Most of that expanse is outside the native range of Monterey pine and cypress.  Griffiths and Villanova do not acknowledge that both Monterey pine and cypress are being eradicated outside their native range for the same reason that eucalyptus is being eradicated, i.e., they are considered “alien invaders” where they have been planted outside their native range.  Here in the San Francisco Bay area, for example, 500 Monterey pines were destroyed on the Marin headlands a few years ago and an untold number of Monterey pines will be destroyed by the FEMA projects in addition to those that have already been destroyed here.

If, in fact, monarchs do have a preference for Monterey pines and cypress for their winter roost, they do not have that option outside of the small native range of those trees in Monterey County. 

For the record, we should tell you that we are just as opposed to the pointless destruction of Monterey pine and cypress outside their small native range as we are opposed to the destruction of eucalyptus.

There is paleontological evidence (fossil cones) that Monterey pines lived in the San Francisco Bay Area several times in the distant past.  That finding was reported (4) in Fremontia, the journal of the California Native Plant Society.  The author asked that Monterey pines be allowed to remain where they lived in the past because the species is threatened in its small native range.  Unfortunately, her advice has been ignored by native plant advocates, who continue to demand that all Monterey pines be destroyed where they have been planted outside their present native range.  This extreme viewpoint is one of the reasons why native plant advocates have earned their reputation as fanatics.

Myth #2:  The California migration of monarch butterflies used exclusively native trees before eucalyptus was planted in California.

Those who wish to discount the value of eucalyptus to overwintering monarchs often assume the California monarch migration predates the planting of eucalyptus in California in mid-19th century.  That assumption supports their claim that all of our eucalyptus can be destroyed without having a negative impact on monarch butterflies.   In fact, there is no historical record of the monarch migration until the mid-19th century.  The historical record of the monarch migration was reported by Vane-Wright (3), who tells us the California monarch migration is probably a 19th century expansion of the range of the eastern monarch migration, from east of the Rocky Mountains to Mexico.  Recent molecular analysis of the monarch migration confirms that the eastern and western migration of monarchs in North America are genetically identical, suggesting that the populations might be dispersing east and west from their Mexican winter roost. (5)

Monarch caterpillar on milkweed. Tilden Botanical Garden

Monarch caterpillar on milkweed. Tilden Botanical Garden

Monarch butterflies are not usually eaten by birds because their host plant contains a toxin that makes birds sick and the monarch’s warning colors broadcast that fact.  The warning colors of butterflies that are toxic to birds are often mimicked by other species of butterflies to confer that protection.  There is a monarch mimic, the Viceroy, in the eastern US, which occurs in California only in a tiny bit of riparian habitat in southeast California.  “The lack of mimics suggests the [monarch] may not have been here long enough for any to evolve.” (6)

Myth #3: Non-native species of milkweed is harmful to monarch butterflies.

Monarch butterflies lay their eggs on milkweed and their larvae, the caterpillar, feeds exclusively on milkweed.  Many native plant advocates believe that the monarch requires a native species of milkweed.  They are mistaken in that assumption.  Wikipedia lists over 35 species of milkweed (genus Asclepias) all over the world and many are known to be used by the widely dispersed populations of monarchs.

The dispersal of monarchs from their original range in North America is approximately 200 years old, according to molecular analysis of populations across the Pacific Ocean (Hawaii, Samoa, Fiji, New Caledonia, New Zealand, Australia) and across the Atlantic (Spain, Portugal, Morocco).  These dispersals are assumed to have been aided by human transportation of both milkweeds and monarchs and extreme weather events.  “For example, monarchs were recorded in Australia in 1870 and were most probably carried there on cyclonic winds from a source population in New Caledonia.” (7)  These populations do not migrate and are therefore genetically distinct from the ancestral population of North American monarchs as a result of genetic drift.

In many of the homes of new populations of monarch butterflies there was no native species of milkweed before being introduced simultaneously with the monarch populations.  Although there are numerous members of the milkweed family native to Australia, monarchs do not appear to utilize the native species, preferring the introduced species of milkweed.

Tropical milkweed (Asclepias curassavica) Creative Commons

Tropical milkweed (Asclepias curassavica) Creative Commons

In California, a tropical species of milkweed is popular with gardeners (Asclepias curassavica).  Unlike the native species of milkweed, tropical milkweed does not die back in winter.  Gardeners therefore tend to prefer the tropical milkweed because it makes a colorful contribution to their gardens year around.

Of course, native plant advocates prefer native species of milkweed and they justify their preference by claiming that tropical milkweed is harmful to monarchs.  They claim that the monarch parasite (Ophryocystis elektroscirrha) can accumulate on tropical milkweed because it doesn’t die back during the winter.  Tropical milkweed is the only milkweed available in winter.  The parasite disrupts some winter breeding of monarchs, but that breeding would not occur in the absence of tropical milkweed.  If more monarchs are the goal, tropical milkweed is making a contribution to the monarch population.

New scientific research bebunks the myth that tropical milkweed is harmful to monarchs.  Leiling Tao et.al. (8) studied monarch lifespans when they fed on a variety of milkweed species.  They looked at both resistance to monarch parasite (O. elktroscirrha) infection and tolerance once infected.  They found a complex interaction between species of milkweed the monarchs fed on and the amount of mycorrhizal fungi on the roots of the milkweed.  But one result was clear:  monarchs raised on tropical milkweed (A. curassavica) lived as long, or longer than, monarchs raised on other species of milkweed.  They were less likely to be infected, and once infected, tolerated the infection well.  In short, there is nothing about tropical milkweed as a host that is detrimental to monarch survival in the presence of parasites.

Native plant advocates also speculate that tropical milkweed can disrupt the migratory patterns of monarchs because it is available when native milkweed is not available.  Given that monarchs have persisted for 200 years all over the world, using exclusively non-native milkweed and without migrating, this seems an unnecessarily pessimistic concern.  Neither native milkweed species, nor migration are essential to the survival of monarchs as a species.

Peek under the cover story

As we often do on Million Trees, we have taken a peek under the cover story being used by native plant advocates to justify the eradication of non-native plants and trees.  Once again, we find a lot of pessimistic speculation, but little evidence that eradicating non-native plants will benefit wildlife, or conversely that wildlife can only survive in native habitat.  Yes, it was a tedious journey to that conclusion and we thank you for your patience if you have persevered to our optimistic conclusion that wildlife is far more resourceful and resilient than nativism wishes to believe.

Monarch butterfly in San Francisco. Copyright Janet Kessler

Monarch butterfly in San Francisco. Copyright Janet Kessler


(1) Dennis Frey and Andrew Schaffner, “Spatial and Temporal Pattern of Monarch Overwintering Abundance in Western North America,” in The Monarch Butterfly Biology and Conservation, Cornell University Press, 2004.

(2) Jessica Griffiths and Francis Villablanca, “Managing monarch butterfly overwintering groves:  Making room among the eucalyptus,” California Fish and Game 101(1): 40-50; 2015

(3) Richard Vane-Wright, “The Columbus Hypothesis:  An Explanation for the Dramatic 19th Century Range Expansion of the Monarch Butterfly,” in Biology and Conservation of the Monarch Butterfly,Natural History Museum of Los Angeles County, 1993.

(4) Constance Millar, “Reconsidering the Conservation of Monterey Pine,” Fremontia, Vol. 26, No. 3, July 1998

(5) Justine I. Lyons, et. al., “Lack of genetic differentiation between monarch butterflies with divergent migration destinations,” Molecular Ecology, (2012) 21, 3433-3444

(6) Art Shapiro, Field Guide to Butterflies of the San Francisco Bay and Sacramento Valley Regions, California Natural History Guides, UC Press, 2007.

(7) Amanda Pierce, et. al., “Serial founder effects and genetic differentiation during worldwide range expansion of monarch butterflies,” Proceedings of the Royal Society of Britain, 281: 2014.2230.

(8) LeilingTao, et. al., “Disease ecology across soil boundaries:  effects of below-ground fungi on above-ground host—parasite interactions,” Proceedings of Royal Society of Britain, 282: 2015.1993.

San Francisco Fells More Trees – Treasure Island

DSCN0052 - the beautiful trees of Treasure Island San Francisco - soon to be gone 2016

People have started writing to us about hundreds, perhaps thousands, of trees being clear-cut on Treasure Island – beautiful, healthy trees being destroyed. It’s happening right now.

One person wrote: “Over on the area where officers quarters are, there appears to be clear cutting is there any thing that can be done to save the ones left?

Then he sent us these pictures with the note: “Thanks for your attention to these matters. I am just a beer drinking football watching person, but perhaps I am more naive than I thought, because what I saw as represented by these images … was disturbing to a city person like myself.

DSCN0008 trees felled and dumped -Treasure Island san francisco 2016

 

DSCN0021 stumps and piles of mulch are all thats left - treasure island san francisco 2016

“These trees appear to have been just killed and then ground down to saw dust with no thought of conservation, reuse or anything, unconscionable,” he added.  I doubt the proud city of San Fran will ever mitigate the amount of trees they are killing today.”

huge old trees cut down on treasure island san francisco 2016Another person wrote:

“[On Treasure Island] I drove past several spots on the island where eucalyptus have been completely clear cut. I was driving so I couldn’t really get a good estimate, but it looks like many hundreds. Many of the trees were VERY large and healthy looking. They are already being chipped and/or logged…

“The work of the nativists? Looks like it to me. Otherwise why remove entire stands of healthy trees?

“I, for one, am sick and tired of this disgusting, unsupportable destruction that has no scientific or practical basis. These actions go beyond normal landscaping or aesthetic decisions. The city will suffer the effects of these actions for decades to come.

“Frankly, I’m also disappointed that the main opposition relies so heavily  on scientifically unsupportable counter-arguments. It makes it very hard to find effective ways to combat the destructive philosophy that has taken over Parks and Rec.”

DSCN0020 stumps and piles of mulch are all thats left - treasure island san francisco 2016

The huge eucalyptus trees of Treasure Island are among the sites where Monarch butterflies have been known to overwinter. Eucalyptus trees are great at sequestering carbon because of their dense wood, their fast growth, their huge size, and their long lives… if they’re not cut down like these trees here.

  • How many tons of sequestered carbon are now being released?
  • How much monarch butterfly over-wintering habitat has been destroyed?
  • How much tree cover for birds and animals has been removed?

How can San Francisco call itself a green city with this tree canopy shrinkage going on in these times of global warming?

monarch butterfly in a San Francisco eucalyptus tree - copyright Janet Kessler

Season’s Greetings with Monarch Butterflies

Monarch butterfly in San Francisco - copyright Janet KesslerIt’s a lovely coincidence that here in California, the holiday season is Monarch butterfly season. We bring you this post (partially based on a post from SutroForest.com, used with permission) to celebrate the season with butterflies.

We wish all our readers and supporters a wonderful holiday season, and a happy and fruitful year in 2016.

THE WESTERN MIGRATION OF THE MONARCH BUTTERFLIES

Unlike the Monarchs east of the Rockies (which migrate from Canada to Mexico and back), the butterflies in the West migrate between the interior and the coast. The butterflies east of the Rocky Mountains go south to Mexico in winter. The butterflies on the Western side come to the California coast in search of warmer, milder weather than the inland winters.

From November to February, monarch butterflies gather in thousands in tall trees by the coast.

fallmigrationmap usfws

One of the wonderful things eucalyptus trees do is provide wildlife habitat. In particular, they are crucial to supporting the Western Migration of the the Monarch butterflies, by providing a roost for the butterflies to spend the winter. A study by Dennis Frey and Andrew Schaffner of 300 over-wintering sites showed that three-quarters of them were in eucalyptus trees. In fact, there’s some evidence that the butterflies’ Western migration exists because of the eucalyptus trees.

Most winters, you can see the butterflies at Natural Bridges State Park, about an hour and a half south of San Francisco. Some years they’re even found right in San Francisco, in places like the Presidio and Treasure Island. This is one of those years: The Monarch butterflies came to San Francisco and also to Oakland’s Aquatic Park.

MONARCH BUTTERFLIES IN SAN FRANCISCO IN 2015

Janet Kessler visited the Presidio and took these lovely pictures of Monarchs on the eucalyptus trees there. They’re published here with permission.

monarch and shadow on eucalyptus copyright Janet Kessler

monarch butterfly in a San Francisco eucalyptus tree - copyright Janet Kessler

Monarch butterfly on eucalyptus leaf - copyright Janet Kessler

CHILDREN DRAW MONARCHS

Also in celebration, we’re proud to publish these pictures from Girl Scout Troop #61902, sent in by Alma Sorenson, Troop Leader:

Grace-'Untitled' sm

Monarch Butterfly – by Grace M.

Addy-'The Monarch in Golden Gate Park' sm

The Monarch in Golden Gate Park – by Addy

Emma-'Take Flight' smm

Take Flight – by Emma

Angelina-'One Monarch in a San Francisco Eucalyptus Tree' sm

One Monarch in a San Francisco Eucalyptus Tree – by Angelina S.

Lindsey-Monarch Butterflies Love Eucalyptus Trees' sm

Monarch Butterflies Love Eucalyptus Trees – by Lindsey D.

 

Troop 61902 Sign sm

Girl Scouts: Building girls with courage, confidence, and character who make the world a better place

From Ms. Sorenson:

“We are a troop of twelve 4th and 5th grade Juniors from five different San Francisco schools focused on learning and earning Girl Scout badges, and on serving our community.

“We have our donated time and our cookie money to My New Red Shoes, the SFSPCA, and Project Open Hand. This year we will continue our theme of helping kids in need and on the environment.