Sophie Middleton and Adam Smith


  1. Research shows that glyphosate use is reducing the acreage of milkweed growing in the US state of Iowa
  2. Milkweed is both food and habitat for the Monarch butterfly, and Monarch numbers are also decreasing
  3. The observed effect will apply outside Iowa, wherever similar technology is used
  4. Monarchs are also threatened by Bt toxin in corn and pollen
  5. Our Call to Action: write to your representatives and express your concern over GM’s environmental consequences!

The Monarch butterfly (Danaus plexippus) is perhaps the best-known of all North American butterflies, is also native to several European countries and occasionally migrates as far as Western Europe. Unfortunately, thanks to a double-whammy courtesy of genetic modification (GM), its days may be numbered.

Take action now by expressing your feelings on this crucial issue to your democratic representatives!

Our glorious Monarch

The Monarch butterfly is a beautiful creature with an easily recognisable orange and black wing pattern, and is famous for its migration between Canada, Mexico and Baja California that spans the life of three to four generations of the butterfly. As a ‘milkweed’ butterfly, the Monarch relies on common milkweed (Asclepias spp.) for food and habitat, but this plant species is under enormous threat from the increasing use of glyphosate herbicide on Monsanto’s Roundup Ready GM crops.

Getting to the Hartzler of the matter

Bob Hartzler, a weed specialist from Iowa State University, USA, discovered that milkweed numbers suffered following the introduction of Roundup Ready crops, and consequently the use of glyphosate [1]. Fewer milkweed plants means less Monarch butterflies, and unless milkweed is specifically planted elsewhere to provide food for the caterpillars that become Monarchs, their numbers will continue to decrease.

Although Hartzler’s research looked specifically at Iowa, he believes that the decline in common milkweed he observed in Iowan corn and bean fields could reduce Monarch butterfly reproduction in any location with similar cropping patterns.

He's not the only one who is worried.  A study recently published in the journal Insect Conservation and Diversity [2] also shows that increased use of glyphosate herbicide with Roundup Ready GM crops in the North American Midwest is killing milkweed plants. The paper explores other factors contributing to declining Monarch populations, such as deforestation in Mexico, but co-author Chip Taylor, from the University of Kansas, says the rapid increase in numbers of Roundup Ready crops and consequent glyphosate overuse is the major cause. “It’s hard to deny the conclusion,” says Taylor, who has been warning of the negative effects of GM crops since 2001.

Bt toxin is bad news for butterflies

Unfortunately, the problems posed by GM crops for the Monarch don’t end with glyphosate. The presence in corn of Bacillus thuringiensis (Bt) toxin, which is added by biotechnology companies to make the crop resistant to the European corn borer, is similarly deadly to Monarch larvae.  A 1999 study by John Losey [3] and a later paper by researchers at Iowa State University [4] both showed that Bt corn pollen was lethal to the larvae.

The combined effects of Bt and glyphosate represent a tragic pincer movement by GM technology, which threatens to decimate Monarch populations wherever it is used. “It [glyphosate] kills everything.   It’s biodiversity Armageddon,” said Lincoln P. Brower, an entomologist at Sweet Briar College and one of Taylor’s co-authors.

Evidence vs. propaganda

This is devastating news that further highlights how modern, industrial agricultural practice is destroying both flora and fauna. We totally agree with Brower when he says, “It’s atrocious what’s going on, and it’s very easy for the biotechnology companies like Monsanto to propagandize and mislead the public.” With mainstream media singing from the same hymn sheet on the subject, it’s easy to lap up the wonderful, positive press about GM crops and how they will save the world. The truth, however, is slowly coming out, and is very different: GM crops are harmful to both humans and the environment, in many different ways.

Call to Action

  • Wherever you are, write to your democratic representatives at national and European levels, to express your concern over the effects that GM crops are having on the environment
  • Spread this article and others like it far and wide, to counter the pro-GM propaganda that is so prevalent in the mainstream media

[1] Hartzler R. Reduction in common milkweed (Asclepias syriaca) occurrence in Iowa cropland from 1999 to 2009. Crop Protection 2010;29:1542–4.

[2] Brower LP, et al. Decline of monarch butterflies overwintering in Mexico: is the migratory phenomenon at risk? Insect Conservation and Diversity 2011; DOI: 10.1111/j.1752-4598.2011.00142.x.

[3] Losey J, et al. Transgenic pollen harms monarch larvae. Nature 1999;399:214.

[4] Stanley-Horn DE, et al. Assessing the impact of Cry1Ab-expressing corn pollen on monarch butterfly larvae in field studies. PNAS 2001;98:11931–6.


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