Monarch Butterflies



Have you ever seen one of these? It’s a Monarch Butterfly. Every spring, millions fly from Mexico and southern California to other parts of the US and southern Canada. And every autumn, they fly back. On the first of November, called the Day of the Dead, people celebrate the return of the monarchs to the mountainous fir forests of Central Mexico.

But their numbers are dropping. In 1997, there were 150 million. Last year there were only 60 million. One problem is the gradual sterilization of American farmlands thanks to powerful herbicides like Roundup. Monarch butterfly larvae eat a plant called milkweed. But the amount of this plant in Iowa, for example, has dropped between 60% and 90% over the last decade.

And this year was much worse for the monarchs. They came late to Mexico… and I think only 3 million have been seen so far! That’s a stunning decrease!

Some blame the intense drought that hit the US in recent years—the sort of drought we can expect to become more frequent as global warming proceeds.



Earlier this year, Michael Risnit wrote this in USA Today:

Illegal logging in the Mexican forests where they spend the winter, new climate patterns and the disappearance of milkweed—the only plant on which monarchs lay their eggs and on which their caterpillars feed—are being blamed for their shrinking numbers.

Brooke Beebe, former director of the Native Plant Center at Westchester Community College in Valhalla, N.Y., collects monarch eggs, raises them from caterpillar to butterfly and releases them.

“I do that when they’re here. They’re not here,” she said.

The alarm over disappearing monarchs intensified this spring when conservation organizations reported that the amount of Mexican forest the butterflies occupied was at its lowest in 20 years. The World Wildlife Fund, in partnership with a Mexican wireless company and Mexico’s National Commission of Protected Areas, found nine hibernating colonies occupied almost 3 acres during the 2012-13 winter, a 59% decrease from the previous winter.


Because the insects can’t be counted individually, the colonies’ total size is used. Almost 20 years ago, the colonies covered about 45 acres. A couple of acres contains millions of monarchs.

“The monarch population is pretty strong, except it’s not as strong as it used to be and we find out it keeps getting smaller and smaller,” said Travis Brady, the education director at the Greenburgh Nature Center here.

Monarchs arrived at the nature center later this year and in fewer numbers, Brady said.

The nature center’s butterfly house this summer was aflutter with red admirals, giant swallowtails, painted ladies and monarchs, among others. But the last were difficult to obtain because collectors supplying the center had trouble finding monarch eggs in the wild, he said.

No one is suggesting monarchs will become extinct. The concern is whether the annual migration will remain sustainable, said Jeffrey Glassberg, the North American Butterfly Association’s president.

The record low shouldn’t set off a panic, said Marianna T. Wright, executive director of the National Butterfly Center in Texas, a project of the butterfly association.

“It should certainly get some attention,” she said. “I do think the disappearance of milkweed nationwide needs to be addressed. If you want to have monarchs, you have to have milkweed.”

Milkweed is often not part of suburban landscape, succumbing to lawn mowers and weed whackers, monarch advocates point out. Without it, monarch eggs aren’t laid and monarch caterpillars can’t feed and develop into winged adults.

“Many people know milkweed, and many people like it,” said Brady at the nature center. “And a lot of people actively try to destroy it. The health of the monarch population is solely dependent on the milkweed plant.”

The widespread use of herbicide-resistant corn and soybeans, which has resulted in the loss of more than 80 million acres of monarch habitat in recent years, also threatens the plant, according to the website Monarch Watch. In spraying fields to eradicate unwanted plants, Midwest farmers also eliminate butterflies’ habitat.

The 2012 drought and wildfires in Texas also made butterfly life difficult. All monarchs heading to or from the eastern two-thirds of the country pass through the state.


So—check out Monarch Watch! Plant some milkweed and make your yard insect-friendly in other ways… like mine!

I may seem like a math nerd, but I’m out there every weekend gardening. My wife Lisa is the real driving force behind this operation, but I’ve learned to love working with plants, soil, and compost. The best thing we ever did is tear out the lawn. Lawns are boring, let native plants flourish! Even if you don’t like insects, birds eat them, and you’ve gotta like birds. Let the beauty of nature start right where you live.

18 Responses to Monarch Butterflies

  1. Berényi Péter says:

    What did Monarchs do during the ice age?

    • John Baez says:

      I suspect there are too few fossil butterflies to easily answer this question that way. But Monarch butterflies can easily fly 100 miles a day, and they are one of the few insects that can cross the Atlantic. In some years they have been seen in southwest Britain. They are becoming more common in Bermuda, due to increased use of milkweed as an ornamental plant in flower gardens. Monarch butterflies born in Bermuda remain year round due to the island’s mild climate!

      They also reside in New Zealand. Over on Google+, Jeremy Webb notes that

      In NZ the Monarchs do not migrate, but in winter can be found clustering in the thousands in certain trees, so many they look like autumn leaves. See

      http://resources.ccc.govt.nz/files/MonarchButterflies-environmentecology.pdf

      So, I’d expect that if the climate changes slowly enough that milkweeds survive in large numbers, the Monarch Butterfly has a decent chance of going where the milkweeds are.

  2. Arrow says:

    Good news for poor milkweed.

    • John Baez says:

      No, bad news for the milkweed: we’re killing it off, so the food chain it supports may be collapsing. Please reread the article, or this:

      Roundup Ready crops contain a bacterial gene that allows them to withstand Roundup or its generic equivalent, glyphosate, allowing farmers to kill the weeds without harming the crop.

      Because they make weed control much easier, the crops have been widely adopted by farmers. This year, 94 percent of the soybeans and 72 percent of the corn being grown in the United States are herbicide-tolerant, according to the Department of Agriculture.

      That in turn had led to an explosion in the use of glyphosate, according to the Environmental Protection Agency. About five times as much of the weed killer was used on farmland in 2007 as in 1997, a year after the Roundup Ready crops were introduced, and roughly 10 times as much as in 1993.

      Farmers, of course, have always tried to eliminate weeds, by tilling or by spraying other herbicides. But while herbicides often had to be used before crops emerged from the ground, glyphosate can be sprayed later in the growing season because it won’t damage the resistant crops. That and the general effectiveness of glyphosate have led to greater weed control.

      “It kills everything,” said Lincoln P. Brower, an entomologist at Sweet Briar College who is also an author of the paper documenting the decline of monarch winter populations in Mexico. “It’s like absolute Armageddon for biodiversity over a huge area.”

      The amount of milkweed on farms in Iowa declined 90 percent from 1999 to 2009, according to Robert G. Hartzler, an agronomist at Iowa State. His study, published last year in the journal Crop Protection, found milkweed on only 8 percent of the corn and soybean fields surveyed in 2009, down from 51 percent in 1999.

      Because of weed-control efforts, even before the advent of Roundup Ready crops, any one farm is not likely to harbor that much milkweed.

      But the sheer amount of farmland in the Corn Belt has meant that farms, in aggregate, have accounted for a vast majority of monarch births, according to another study published by Dr. Oberhauser and colleagues in 2001. That study estimated that in Iowa, farms produced 78 times the number of monarchs as nonagricultural sites, and in Wisconsin and Minnesota, 73 times as much.

      And while monarchs come from other parts of the country as well, the Midwest is widely believed to be where most of them are hatched.

      Luckily, Dr. Taylor of Monarch Watch offers a way that scientists can address the problem: develop a Roundup-resistant strain of milkweed!

      • Berényi Péter says:

        Or just stop expansion of farmland. Agriculture is far more damaging to the environment than any sane industrial practice can ever be, due to low flux density of its energy source which implies inefficient land use. The same is true for so called renewables for the same reason.

        The main driver behind farmland expansion is the biofuel madness, it is time to put an end to it. No other industry can turn the entire countryside to utter wasteland devoid of all life in autumn (called ploughland). It is a temperate wet desert on a continental scale.

        Only industrial wind farms can come in as close seconds with their extensive network of heavy duty service roads and unbelievably high level of low frequency (< 1 Hz) noise emission, which is not regulated in any way and can't even be measured with standard noise control equipment (one would need mirobarometers to do that).

        Large solar photovoltaic arrays also interfere with wildlife by competing for a diluted energy source. They do not make sense anyway until an economic way to transient energy storage is found. Even then, they should be restricted to surfaces that are put to dual use like rooftops, parking lots and roads.

        If CO₂ emission is a problem indeed, there is no other alternative than to go entirely nuclear with breeder reactors, possibly Thorium based ones. Passive cooling and elimination of long half life isotopes from waste is a must.

      • John Baez says:

        Berényi wrote:

        Or just stop expansion of farmland.

        Right, the big problem is how vast agricultural lands reduce biodiversity, and how some ‘improvements’ in agricultural practices, like the use of Roundup, only intensify that trend. For example, in Europe the population of many bird species has crashed over the last few decades:

        • R.J. Fuller et al, Population declines and range contractions among lowland farmland birds in Britain, Conservation Biology 9 (1995) 1425–1441.

        We used extensive atlas and census data to assess trends in the distribution and population levels of birds on lowland farmland in Britain between the late 1960s and early 1990s. Many species of farmland birds have become less widespread or have declined in numbers, or both, but few have become more wide-spread or have increased. Of the 28 species classified as farmland birds the distributions of 24 contracted between 1970 and 1990. Of the 18 farmland species for which it was possible to assess population change, 15 were less abundant in 1990 than in 1970. Seven of the species were estimated to have undergone population decreases of at least 50%. Farmland species showing the largest population declines tended also to show substantial range contractions. Farmland species underwent an appreciably larger contraction of distribution than species associated with any other habitat. Furthermore, farmland species tended to decrease in abundance, whereas woodland species tended to increase. Population declines among farmland birds became evident in the mid- to late 1970s, a period when several fundamental changes were taking place in British agricultural practices. These included a great reduction in the spring sowing of cereals, a simplification of crop rotations, increased use of chemical pesticides and inorganic fertilizers, and more-intensive grassland management. We suggest that the declines of farmland bird species have been caused or aggravated by this pervasive intensification of agriculture. Existing research on declining farmland birds, however, indicates that there is no single mechanism underlying the population changes. We identify priorities for research, focusing mainly on relationships between bird populations and agricultural practices, but we also recognize a need for a better understanding of the role of predation.

        I’ve read that the reduction of hedgerows is part of the problem there—eliminating the place where birds and other species can live.

        So, rebel biotechnologists developing Roundup-resistant strains of milkweed is a fun romantic idea, but the serious business is 1) finding farm practices that are efficient yet don’t damage biodiversity as much as currently popular ones, 2) stopping the insane government subsidies of biofuels, especially corn-based ethanol in the US.

        I don’t know how damaging wind and solar plants are; stuff can grow around wind turbines. But I agree completely that we need to push for thorium reactors.

        • Ian MacKenzie says:

          Several things…

          Dawson College in Montreal, where I teach, is involved in a program called Monarchs Without Borders, run by the Jardin Botanique de Montreal — it gets people involved in raising and tagging caterpillars/butterflies. Great idea and program

          http://espacepourlavie.ca/en/monarchs-without-borders-monarch-raising-kit

          Participants who tag successfully are in fact contributing to research run out of the U of Kansas by Chip Taylor — see http://www.monarchwatch.org/

          Re: “reduction of hedgerows” — do you have a source on that? I too recall reading something somewhere on this topic. In my rural childhood (in southern Ontario) all the fields were 5-10 acre units marked off by thick hedgerows of that harboured all kinds of trees, plants, birds & critters. With the vanishing of the smaller family farms and the elimination of garden crops by (you said it) corn, the hedgerows disappeared. Easier driving the big combine; too bad the top soil blows away faster.

          Another factor in reduced bird populations is apparently cutting for hay multiple times over the growing season versus once or twice as was once the case. Where ground nesting species once had a chance to reproduce before the mid-to-late summer haying, now the bigger fields are cut early and often, 4 or 5 times, by rotary mowers. They skip the baling and blow it right into trucks to be hauled off to the feedlots.

          Always enjoy dropping in on your blog John! Sustainability needs a healthy, expanding population of math nerds…

      • Arrow says:

        Monarch decline is certainly good news.

        We are bad news, but that’s hardly news really. Also I don’t see any general population numbers for milkweed in the article, only information that it is much less prevalent on farmland but it doesn’t follow that its total population experienced as sharp a decline as that of butterflies.

  3. For years I have been finding eggs on milkweed in my yard and “raising” the caterpillars in a tank on my porch until the butterflies are ready to be released. This summer I sadly had less than a quarter of my normal number of monarchs and attributed it to the post-Sandy ecosystem disruption in my Jersey shore area. I see the reason is much broader and more disturbing.

  4. Reblogged this on 4writersandreaders and commented:
    Learn about our Amazing Monarchs! ~ Bette A. Stevens http://www.4writersandreaders.com

  5. I hate this. We used to have so many of them cover over our area and we had only a handful this year. What a tragedy. They are such awesome butterflies and the journey they make twice a year is of epic proportions. So sad. Natalie :(

    • John Baez says:

      I hate it too. Vote for politicians who care about the environment, help lobbies who pressure the politicians to do the right things, and tear out your lawn and grow plants that birds and insects like—those are some of the main things we can do.

  6. John Baez says:

    Ian McKenzie—I’m glad you enjoy this blog! And I’m glad to hear about Monarchs Without Borders. Cutting for hay multiple times a year… that’s the kind of thing that could have a huge effect. How come they can do it now? Do they get the hay to grow faster, or just cut it more often?

    As for the elimination of hedgerows causing a collapse of bird populations, I’ve mainly heard about that in Britain and Europe.

    • Robin McKie, How EU farming policies led to a collapse in Europe’s bird population, The Guardian, 26 May 2012.

    These grim statistics are for the whole European Union. The article writes:

    This dramatic decline represents a 50% reduction and is blamed on major changes in farming policies enforced by the EU over the last 30 years.

    In order to boost food production across Europe, the wholesale ripping up of hedgerows, draining of wetlands and ploughing over of meadows has robbed farmland birds of their homes and food.

    The article is based on data from the Pan-European Common Bird Monitoring Scheme, and their website has more on bird populations. But for more on hedgerows we have to look elsewhere, like this:

    • S. A. Hinsley and P. E. Bellamy, The influence of hedge structure, management and landscape context on the value of hedgerows to birds: a review, Journal of Environmental Management 60 (2000), 33–49.

    In this review, we discuss the value of hedgerows as bird habitat in lowland-farming landscapes to provide a background against which decisions concerning hedgerow management might be evaluated. The two most important factors positively associated with species richness and abundance of breeding birds in hedgerows are hedge size (height/width/volume) and the presence/abundance of trees. The provision of cover and the botanical and structural complexity of the vegetation are also important. However, large hedges do not suit all species; birds tend to prefer hedgerow types which most closely resemble their usual non-hedgerow breeding habitat. The value of hedgerows to birds can be increased by combining them with other features such as headlands (for game birds), verges, wildflower strips, game and wild-bird cover and well-vegetated banks and ditches. The presence of well-grown, dead or decaying trees is beneficial to many species, providing nest holes, foraging sites and perches. Increasing the structural complexity of a hedgerow and its associated habitat may also reduce the incidence of predation. Hedgerows also provide physical shelter and roost sites and are an important source of winter food supplies, especially berries and other fruits. Some bird species, usually those whose primary habitat is woodland, live mainly within the hedgerow itself, whereas others are more dependent on the surrounding landscape to a greater or lesser extent. However, even the presence of woodland bird species is influenced by the availability and characteristics of alternative habitats in the surroundings and therefore hedgerows and their bird populations do not function as isolated patches. As linear landscape elements, hedgerows also provide safe cover for both local and larger-scale movements and may facilitate access to resources or habitat which might otherwise be too risky or too remote for birds to use or colonise. A number of recommendations for improving hedgerow habitat for birds are reiterated from an extensive literature and include combining hedgerows with other semi-natural habitat, providing a variety of structural types, maintaining good cover in the hedge-base, e.g. by excluding stock and herbicide, and avoiding excessive cutting. However, good hedgerow management has costs and is unlikely to be applied widely in the absence of national policy and funding.

    In England, where there’s a lot of popular support for wildlife, people are trying to reverse the decline of bird populations:

    • Fiona Harvey, UK’s wild bird population continues to decline, The Guardian, 17 October 2013.

    The number of wild birds in the UK is still falling, despite efforts to protect them by changing farming practices.

    Conservationists have urged the environment secretary, Owen Paterson, to use the money newly available from the EU’s common agricultural policy to step up protection measures.

    Since 2003, there has been a 13% decline in the population of farmland birds. In the five years to the end of 2012, the decline was 8% overall. The decline has slowed, according to the Wild Bird Indicator statistics released by the government on Thursday, and some species are in better health than they were in the 1970s when data began to be comprehensively collected. However, conservationists are concerned that the drop in numbers is continuing, with a halving of farmland bird numbers in the past 40 years. Woodland birds are down 17%.

    Turtle doves have had their lowest level of sightings since records began. Lapwings are down by nearly two thirds since 1970, while corn buntings are down nine-tenths in the same period, and the number of skylarks is down by well over half.

    But jackdaw numbers have gone up by 140% since 1970, and the increasingly common woodpigeon is up by a similar amount.

    Farmland birds suffer from intensive agriculture, as farmers often remove or drastically cut back the hedges and trees where many of them live, while pesticides can leave them with less prey, and a lack of wild field margins cuts down on habitats.

    There are some government-sponsored schemes to encourage farmers to make room for wildlife, for instance by leaving field margins wild, cutting down on pesticide and artificial fertiliser use, and leaving some areas fallow or pasture. There are also strict laws against killing rare birds of prey, but conservationists think these are frequently flouted.

    Martin Harper, conservation director at the RSPB bird charity, said: “The trend for farmland birds continues to go downwards. The decline has slowed, and wildlife friendly farmers who put conservation measures in place on their land must be congratulated for their hard work. But if we are all going to work together to bring wildlife back to our countryside, then the funding must be there for these measures to continue.”

    Under the reforms to the common agricultural policy, which were agreed this summer, the government has the ability to divert some of the millions of pounds of funds available – which come ultimately from taxpayers – to environmental stewardship schemes to reward farmers for good practice.

    The environment secretary, Owen Paterson, has still not said how he intends to allocate the funding, which could go up to 15% of the agricultural subsidies budget. But given the government’s freedom of action under the new rules, much of it could go to farmers based not on their practices but on the amount of land they farm, as other subsidies are.

    A decision is expected before the end of the year, and green groups are concerned that the amount devoted to environmental measures will not be enough to halt further declines in wildlife numbers. “Without Owen Paterson’s help, farmland wildlife will continue to struggle, along with those farmers trying to help,” said Harper.

    A Defra spokeswoman said: “Agri-environment schemes play a vital part in providing benefits for wildlife and will continue to be an essential element of the next rural development programme.”

  7. lee bloomquist says:

    Yes, I am grateful to have seen many. But recently I have not seen any.

    Our house is alone in the woods within hearing distance of Lake Michigan. One spring day we went outside to sit together in the sun. There, were dozens and dozens of them flying above us in a patch of sunlight streaming through the trees.

    And they were dancing with each other– in pairs! I watched one couple, which after a while flew apart. One of them flew to the siding on our house, moved its wings slowly after coming to a rest, and then bathed there in the sun. I watched it for a while. Suddenly it cocked its wings. Why? It’s partner was flying straight toward it, out of the trees, from its own resting place in the woods. In response it lept from the siding into the air and flew straight toward its onrushing partner. They came ever so close to each other, and then danced away, together, above us in the sun.

    It is the tragedy of the commons. Nobody wants to see things like this destroyed. But something that nobody wants to see happen is nonetheless happening.

    IMHO this is the consciousness of prosperity, manifesting prosperity, and nothing else– specifically, being unconscious of the dignity that this kind of prosperity can take from others, and being unconscious of the peace that can exist inside a human heart, just from living on the planet Earth.

    (My apologies for waxing poetic. You started it.)

  8. millynomad says:

    I saw them in Mexico this time last year! They’re beautiful. A few words here http://millynomad.wordpress.com/2013/11/29/a-million-butterflies/

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