27 February 2021

Plight of the Monarch butterfly - updated

The graph above was published in the Badger Butterflyer - the e-newsletter of the Southern Wisconsin Butterfly Association.  The bar graphs depict the 20-year trend of the acreage in Mexico utilized by overwintering Monarch butterflies.  This past December's 1.66 acres of wintering butterflies is the lowest ever recorded since recordkeeping began.

The cause is multifactorial, including loss of habitat in Mexico and weather/climate changes, but the principal factor is believed to be loss of milkweed - the Monarch's ONLY food plant.  An article at Slate takes up the story:
More than a million acres of Upper Midwest grassland have been plowed under in recent years for corn and soybean fields—a rate of loss comparable to deforestation in places like Brazil and Indonesia. Demand for these crops has surged with the rise of biofuels. At the same time, technology enabled farmers to squeeze ever more from each acre. For monarchs, the most important development was Roundup Ready corn and soybeans.

Since the turn of the century, these genetically modified crops have risen to
dominance in the Midwest. Designed to withstand dousing from the Monsanto company’s Roundup weed killer, the plants enabled farmers to swiftly kill competing weeds, including milkweed, while leaving their crops untouched. In 2013, 83 percent of all corn and 93 percent of soybeans in the United States were herbicide tolerant, totaling nearly 155 million acres, much of it in the Midwest.

It’s no coincidence monarchs faltered at the same time. Karen Oberhauser, a conservation biologist at the University of Minnesota, and a colleague estimated that as Monsanto’s Roundup Ready corn and soybeans spread across the Midwest, the amount of milkweed in farm fields fell by more than 80 percent. Oberhauser determined that the loss of milkweed almost exactly mirrored the decline in monarch egg production...

Already, Iowa farmland has lost more than 98 percent of the milkweed that was once there, according to Iowa State University biologist John Pleasants, who worked with Oberhauser. He’s seen firsthand the transformation as he has studied cornfields during the past decade and a half. Before Roundup, patches of milkweed grew among the corn and along the edges of fields. After the herbicide—nothing but corn... 
Here's the advice that Michigan State University's agricultural extension service offered its subscribers:
Common milkweed, asclepias syriaca, can become a serious problem over time in no-till fields and hay and pasture fields where glyphosate-resistance in the crop is not an option. This weed has an extensive and deep root system and is tolerant to many common herbicides. Multiple herbicide applications are often required...

In glyphosate-resistant crops, milkweed control is not difficult to control. Glyphosate [Roundup], when applied at the proper rate and timing, will give good control. In glyphosate-resistant corn and soybeans, milkweed should be treated with glyphosate at 0.75 lbs a.e./acre glyphosate to control or suppress milkweed. It is always recommended to include 17 lbs spray-grade ammonium sulfate per 100 gallons of water. Late, post-emergent applications when plants are in the bloom stage will be most effective in killing roots...

In hay or pasture, milkweed can be spot-treated with glyphosate applied with a wipe-on applicator while the milkweed is taller than the crop, or spot-treated with a hand-sprayer. When these fields are rotated or renovated, that is the time to make your best effort to deal with milkweed aggressively. Fence rows, field borders and nearby, non-crop areas should be monitored and any milkweed found should be controlled.
And this from Britain's Guardian:
The announcement [of the decreased Mexican overwintering population] followed on the heels of the 20th anniversary of the North American Free Trade Agreement, which saw the United States, Mexico and Canada signing environmental accords to protect migratory species such as the Monarch. At the time, the butterfly was adopted as the symbol of trilateral cooperation.

“Twenty years after the signing of NAFTA, the Monarch migration, the symbol of the three countries’ cooperation, is at serious risk of disappearing,” said Omar Vidal, Omar Vidal, the World Wildlife Fund director in Mexico.
This coming weekend I will be attending the annual late-winter Garden Expo here in Madison, where thousands of cabin-fevered Midwesterners will flock to see the latest in garden products and technology.  I'll be helping staff the information booth for SWBA;  I hope to be handing out ziplock baggies of milkweed seeds to likeminded people who want to do something to help sustain the Monarchs. 

Reposted from 2014 to add some new data (excerpts from a press release by the Monarch Joint Venture and a report by CBS News):

[Note:  the bar graph at the top of this post depicts forest area occupied by Monarchs from 1994 to 2013.  This graph updates the numbers with seven more bars through the end of 2020] 
"The government commission for natural protected areas said the butterflies’ population covered only 2.1 hectares (5.2 acres) in 2020, compared to 2.8 hectares (6.9 acres) the previous year and about one-third of the 6.05 hectares (14.95 acres) detected in 2018...

Gloria Tavera, the regional director of Mexico’s Commission for National Protected Areas, blamed the drop on “extreme climate conditions,” the loss of milkweed habitat in the United States and Canada on which butterflies depend, and deforestation in the butterflies’ wintering grounds in Mexico."
"Illegal logging in the monarchs wintering rounds rose to almost 13.4 hectares (33 acres), a huge increase from the 0.43 hectare (1 acre) lost to logging last year.

Jorge Rickards of the WWF environmental group acknowledged the lost trees were a blow, but said “the logging is very localized” in three or four of the mountain communities that make up the butterfly reserve.

In addition, wind storms, drought and the felling of trees that had fallen victim to pine beetles or disease, caused the loss of another 6.9 hectares (17 acres) in the reserve, bringing the total forest loss in 2020 to 20.65 hectares (51 acres). That compares to an overall loss of about 5 hectares (12.3 acres) from all causes the previous year...

Tavera also expressed concern about the severe winter storms in Texas, which the butterflies will have to cross — and feed and lay their eggs — on their way back to their northern summer homes in coming months.
“This is a cause for worry,” Tavera said, referring to whether the monarchs will find enough food and habitat after the winter freeze."


  1. Godspeed :(

    Not at all meaning to diminish the tragedy you describe, Stan, but i can't help thinking that the plight of the Monarch is a relatively high profile endangerment story, amongst the untold thousands or millions of perhaps never-to-be-told stories concerning species without such a popular following :(

    1. "Not at all meaning to diminish the tragedy you describe, Stan, but i can't help thinking that the plight of the Monarch is a relatively high profile endangerment story, amongst the untold thousands or millions of perhaps never-to-be-told stories concerning species without such a popular following :("

      I suspect that saving the Monarch will go a ways toward saving other species. It's not like any of them live in a vacuum.

  2. If you were at all inclined to mail out baggies of milkweed seed, I'd be glad to email you my address. I live in Chicago and have some garden spots in front of the apartment that I could plant milkweed in, and I could also seed bomb some vacant lots.

    1. This comment has been removed by a blog administrator.

    2. Bridgid, I would be pleased to mail you some seeds for two different types of milkweed (if I can find them out in my garage under the winter's detritus). Drop me an email at the address in the "About Me" segment in the right sidebar.

  3. Perhaps a facebook group could be made? I see FB as vulgar despite being in my 20's and thus in its exact marketing crosshairs, but its crowdsourcing potential cannot be ignored. If you started a milkweed planting group with a suitably eloquent and concise catchphrase and (more importantly) endearing image, you could revitalise the species! Living in Sydney, there's little i can do to help.

  4. So what I am hearing is that some high minded graduate student in cellular botany should make us some glyphosate-resistant milkweed seeds that we can plant all over.

  5. How terribly sad! I remember lots of milkweed and lots of Monarchs from my youth in Wisconsin. I hope the Monarchs can be saved.

  6. I too would like to help. I live in Northwest Arkansas and have dedicated my large front beds to humming birds. I attract a lot of butterflies and I love the monarch. In the 60's the migration came by my house in Tennessee and it was a sight to see. Send SEEDS!!!

    1. I would be pleased to mail you some seeds for two different types of milkweed (if I can find them out in my garage under the winter's detritus). Drop me an email at the address in the "About Me" segment in the right sidebar.

  7. I would like to plant milkweed... is it as simple as harvesting the late summer downy things that pop out of the pods??

    1. Absolutely. That's what nature does. There are additional tips for serious gardeners at Monarch Watch:


    2. I am an avid gardener, but even more a serious insect admirer. Thanks for the link.

  8. Glyphosate was developed by Monsanto, but the patent expired in 2002. So let's give (dis)credit where (dis)credit is due.

    According to Wikipedia: Glyphosate is marketed in the United States and worldwide by many agrochemical companies, in different solution strengths and with various adjuvants, under many tradenames: Accord, Aquaneat, Aquamaster, Bronco, Buccaneer, Campaign, Clearout 41 Plus, Clear-up, Expedite, Fallow Master, Genesis Extra I, Glyfos Induce, Glypro, GlyStar Induce, GlyphoMax Induce, Honcho, JuryR, Landmaster, MirageR, Pondmaster, Protocol, Prosecutor, Ranger, Rascal, Rattler, Razor Pro, Rodeo, Roundup, I, Roundup Pro Concentrate, Roundup UltraMax, Roundup WeatherMax, Silhouette, Touchdown IQ.[29][30][31]
    Manufacturers include Bayer, Dow AgroSciences, Du Pont, Cenex/Land O’Lakes, Helena, Monsanto, Platte, Riverside/Terra, and Zeneca.[31]

    Then again, Monsanto, in a stunning example of vertical market integration, has genetically engineered Round-Up Ready™ corn and soy hybrids, which are also licensed to other seed companies.

  9. If you actually can be bothered to Google Monsanto you will find that it is a company who are out to make money any way they can no matter what.
    Until we repeal the Corporation act they, and all the other Corporations, will use your, yes it is your money, in your pension fund or savings account, that finances them while they destroy everything.
    All you folks who want it all now with a good retirement are fuelling the worlds destruction.
    Good luck.

  10. We have 32 acres and let the milkweed grow everywhere, but I saw not one Monarch this past summer. Sadly.

  11. It is a mistake to look at any short-term graph of numbers and assume that the early portion are representative of all the past history. And 30 years IS short term.

    The 1996 and 1995 peaks may or may not be anomalies in themselves.

    Salmon counts vary a LOT and they do it in some sort of pattern of high and low periods. Those periods last about 30 years - ~30 high, and then ~30 low, back and forth. Each shift is called a "regime". There is little to no middle ground - it is in one state or the other, high or low. It is by the work of salmon biologist Steven Hare, in fact, that the climate oscillation called the "Pacific Decadal Oscillation" (PDO) was discovered - not from climate, but from salmon counts. The "shift" from one regime to the other happens within a year or two. The PDO shift from one regime to the other occurred in the early 2000s. It somewhat appears that the monarch numbers also shifted about that same time.

    So, there is a possibility that monarchs are also affected by the PDO or some similar climatic oscillation.

    To assume that the observed decline over such a short period is due to any one factor or the FIRST possible factor that comes to mind. Environmentalists have a habit of assigning blame for things without any basis at all. The numbers are the numbers, yes, but what the cause is will be in question for some time. Yes, they may holler and scream that "We don't have time! Look at that chart!" but that would be a mistake.

    I will go on record - in my non-panic mindset - as saying the numbers will recover.

    I will aslso point thsese two things out:

    1.) The article says "The bar graphs depict the 20-year trend of the acreage in Mexico utilized by overwintering Monarch butterflies."

    2.) Wiki says "In one study monarchs released during the fall migration from Albuquerque, New Mexico were found overwintering in California and in Mexico."

    This combination of facts should tell us that counting the ones in the Michoac√°n preserve are only part of the story.

    Thus, this whole story is more complicated than most of us commonly believe. Simple approaches, therefore, are likely to bring us to over-simplified and premature conclusions.

    1. You work for Monsanto, don't you?

  12. For a number of years now, I've encouraged milkweed in my yard (by gathering seeds before they blow away and distributing around and so on), but I worry that a few plants here and there isn't going to actual do much to help Monarchs or other species.

    I don't think I've ever seen a Monarch in my garden (in Wisconsin), and it feels like there's a bit of a food desert in terms of other plants. I live in what feels like a very suburban neighborhood, with lots of people spraying poisons and such, and not many people trying to grow native plants or flowers. (I think most of my neighbors hate my yard because the lawn is more weedy than not.)

    1. You're probably correct that the presence or absence of several milkweed plants in your yard will not have a significant impact upon survival of the species. The presence of the plants in a suburban garden does serve as a kind of "signal" to passersby that "here lives a person who is concerned about the environment." If neighbors object, you can probably do as much for butterflies in general by planting a broad range of flowering nectar plants.

      You might also consider removing the seed pods from your milkweed plants in the autumn before they open and spread their seeds; I do that in our neighborhood even though none of my neighbors object to the presence of the plant, because I do realize that some of them are concerned about the "weed" part of the name. (I take the seedpods elsewhere to distribute along roadsides etc).

  13. In Marjory Stoneman Douglas' "Everglades: River of Grass," one of the attached essays spoke of how nesting areas for birds had decreased due to drainage of large portions of the Everglades, the salt water from the Gulf gaining greater purchase in the lower Everglades due to the reduced outward flow of fresh water, and even the farming nutrients in the waters. Some birds moved well north of their usual nesting grounds. Is it possible that butterflies have done the same? That is, they are still out there...but not even in the area where we once found them?

    1. It certainly is possible that new overwintering sites may be found; IIRC, there is mention of the discovery of a small new one in this year's annual report. The complexities involved are large, however - requirements for minimum nighttime temperature, absence of predators, availability of fresh water etc. And the arrivals from the north in the autumn have no way of knowing ahead of time whether a different place fits those needs. Evolution solves that problem by just killing off the ones who choose wrongly.

  14. I noted your comment above from February 5, 2014 about mailing seeds. I just wanted to comment that where I live (northern Maryland) the local county library gives away free milkweed seeds, as does several nature centers and nature preserved. Perhaps people can google to find a place near them.

    Also, it is easy to provide support for solitary bees, an important and often overlooked pollinator. Google provides plenty of information for doing so.

  15. Regarding milkweed: https://tywkiwdbi.blogspot.com/2014/07/milkweed-in-midsummer.html


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