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Monarch butterfly population hits a new low

Sylvia Fallon

Posted January 29, 2014

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The number of monarch butterflies that migrates across the United States each year and overwinters in the forests of Mexico has dropped to an all-time low.  News out of Mexico this morning puts the population at 33.5 million individuals. Although the number of butterflies varies from year to year, this estimate is a precipitous drop from a high of 1 billion in 1997 and down from a long term average of 350 million over the last 15 years.  Furthermore, it represents the 9th consecutive yearly measurement below the long term average.  In other words, this year’s news follows a continuing downward trend. It signals a species in crisis. 


The decline of monarch butterflies over the last decade or more has coincided with the wide-scale adoption of genetically modified crops that are resistant to the weed-killer glyphosate, also known as Round Up.  This change in our agricultural system has led to the near extermination of milkweed from huge swaths of our country.  The problem is that monarch butterflies are dependent on milkweed.  It’s the only type of plant that they use for laying their eggs.

Since the introduction of genetically modified “Round Up Ready” corn and soybeans in the late 1990s their adoption level has reached between 70-90%.  As a result, the use of glyphosate in these crop fields skyrocketed.  Scientists now estimate that in the span of about 10 years (from 1999-2010) there has been 60% decline in milkweeds across the Midwest (in both agricultural and non-agricultural areas) and an 80% decline in monarchs in the Midwest.  Past studies have shown that monarchs from the Midwest comprise 50% of the overwintering population in Mexico. This explains why the loss of butterflies from a specific region could have such a large impact on the overall population size.  

There are, of course, other contributors to the monarch’s decline.  Drought, particularly in Texas, is believed to also be posing a threat to these butterflies as they try to make their way from Mexico across the US to Southern Canada and back in the span of a year.  Climate in general (including drought, but also extreme temperatures) is contributing.  And deforestation of their wintering habitat continues to be a concern.

However, given that the widespread adoption of “Round Up Ready” crops has largely eliminated the monarch’s most essential “habitat” by removing milkweeds from the landscape, it’s time to reconsider whether its continued large-scale use makes sense. Today’s news reminds us just what is at stake. Besides its beautiful appearance and usefulness as a pollinator, the monarch’s long-distance round-trip journey is unique in the insect world, a phenomenon that scientists still don’t fully understand.  If we continue blindly along this path, ignoring the unintended consequences of our actions, we risk losing the monarch’s migration – one of the true natural wonders of our planet.

If you’d like to help the monarchs by planting some milkweed, please visit our green gifts here.  

Photo credit: Image shared via Flickr by Mike Rodriguez

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Rita GuidiJan 29 2014 01:06 PM

The Mexican government is guilty for not protecting these beautiful butterfly and their habitat. They allow people to cut down the trees where these butterflies seek shelter. What a shame...

Patricia JessupJan 29 2014 02:44 PM

Every possible step should be taken to
safeguard. these exquisite,fragile creatures.Why is it that humans seems to have an unlimited capacity to destroy everything that is beautiful
and worthwhile on this planet and can never be
replaced ?

Karen DavidsonJan 29 2014 04:17 PM

Nature needs us to leave it alone. I'm not 100 years old, and I remember finding a DOZEN DIFFERENT KINDS OF BUTTERFLIES IN ONE AFTERNOON. Chances are, you don't. That woods is a mall and parking lot today--not too pretty. If we won't stop until nature is gone and no one remembers how free and beautiful it was, it is a sad day, indeed. STOP with the insecticides and great green lawns. Ask your neighbors to stop. Then plant flowers and bushes that will help PROTECT what is left -- inside and outside your yard. Thank you, thank you, thank you. It can be done.

AngelaGuyJan 29 2014 04:18 PM

We have to do what we can to preserve all species.

Heather MarvJan 29 2014 07:41 PM

The more we mess with Nature, the more mess we create. Pesticides kill everything. We need to get back to the Old ways of doing things, organically, and respecting Nature and using Wisdom as well as good knowledge. Mankind is destroying so much it is evil. Don't use pesticides, use nature things. We need to Create and not destroy.

ButterflyLoverJan 29 2014 09:52 PM

If you want to do something about this, see the book "Raising Monarchs" by Sue Fox McGovern

--- a complete how-to on breeding these beautiful, and now endangered, insects...

Paul CherubiniJan 30 2014 10:11 AM

Monarchs were this abundant in 2010 and 2011 in the GMO croplands of southern Minnesota even though the milkweed that used to grow within the crop fields in the 1990's had been killed off back in 2006-2007: 


In 2012 and 2013 the monarch population was lower (but still this abundant due to a high abundance of monarch egg and caterpillar predators. But the population will soon rebound to the high numbers seen in 2010 and 2011 because there is still enough milkweed to support such numbers.  

sue hartmansueperryJan 30 2014 03:12 PM

Another animal I have said for years now that has diminished here in southern, central New York is the is rare to see one run across the road let alone seeing a carcass (not that I want to) on the shoulder of the road rotting. Is there an explanation other than "US" destroying our world????

Jeffrey ZablowJan 30 2014 05:23 PM

Interesting Comments. May I weigh in? What is actually missing, and missed by the millions who have seen the absence of Monarch butterflies across the US in credible comment from the most respected experts out there, those whose guides and university seats enable them to enjoy the respect and ear of we naturalists out there. Why are they absent from this issue. Why are they silent, and why don't they use their modest ability to assure us of the real fundamentals here. Monarchs are among the most beautiful of all butterflies. I have photographed them for many years, and a fresh Monarch still tantalizes the eye.

Becca RalstonJan 31 2014 09:35 PM

I've certainly noticed the drop in Monarchs. In 2012, I tagged and released over 40 of them. This past summer, I tagged only seven.

Lesley WhitfieldFeb 6 2014 02:04 PM

Have bought some milkweed seeds for my NYC Garden. I hope that these will attract more of the beautiful monarch butterflies. I already have butterfly weed, borage, and bee balm growing. I hope to encourage more butterflies and bees to my garden.

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