Monarch butterfly populations have been on a downward spiral for decades, and the most recent news stories report that monarch numbers have reached an all-time low this year.
There are several reasons why monarchs are a threatened species—including deforestation, parasitism, and ebbing populations of the milkweed plants they depend on. But a new study has reignited the debate over whether or not genetically modified crops are playing a role in the monarch’s decline. Last week the headlines claimed that “GMO Crops Are Killing Butterflies.” Here’s what Grist had to say about it:
We’re all familiar with Big Ag’s bad reputation of picking on small-scale and organic farmers. Now Monsanto and its cronies are beating up an even more innocuous set of victims: beautiful, defenseless monarch butterflies.
Blaming GM crops for monarch declines is nothing new. The controversy began in 1999, when a paper in Nature concluded that pollen from Bt corn—which is genetically modified to carry a Bacillus thuringiensis gene that allows the corn to produce a toxin meant to kill pest insects—could kill monarch butterfly caterpillars. The study was discredited by 2001, but in the interim, “the monarch butterfly rapidly became a public symbol of the environmental hazards of GM crops,” says a report from the Council on Foreign Relations. In fact, monarch declines sparked the first discussion of GMO food labels, according to the CFR report.
The US Senate Subcommittee on Agriculture held the first Congressional hearings on GM foods and in November 1999, legislation was introduced in Congress requiring the labeling of genetically modified foods. The FDA held a series of hearings throughout the United States to reexamine whether GM foods should be considered an additive, thus requiring mandatory labeling, as well as to explore the need for further testing to ensure consumer safety. For its part, the EPA began to review its policies about whether genetically modified seeds should be subject to pest control regulations. And in January 2000, EPA directed companies marketing corn that produces Bt toxin to request that farmers voluntarily plant a buffer zone of traditional corn as a protection for monarch butterflies.
Responding to the widespread fear, the National Academy of Sciences launched a major risk assessment study published in 2001 in the Proceedings of the National Academy of Sciences, which ran a series of articles evaluating the effects of biotech corn on monarch butterflies in the wild. The researchers concluded that Bt-corn’s impact on monarch butterfly populations is “negligible.”
Rick Hellmich, an entomologist with the Agricultural Research Service and co-author of the follow-up report, told National Geographic that “butterflies are safer in a Bt cornfield than they are in a conventional cornfield, when they’re subjected to chemical pesticides that kill not just caterpillars but most insects in the field.”
The latest hubbub over GMOs and butterflies centers around a recent study in Insect Conservation and Diversity. The study does not actually test the hypothesis that GMOs are behind the monarch declines. Instead, the authors’ main conclusion is that “a loss of agricultural milkweeds is a major contributor to the decline in the monarch population.”
GMOs come into the picture because the article cites a 2010 paper which found that milkweed populations on farms declined dramatically between 1999 and 2009, at the same time that Roundup Ready crops were becoming widespread in the Midwest. Roundup Ready crops are engineered to be herbicide-resistant so that farmers can apply weed killers without damaging their crops. The 2010 paper reasons that the widespread adoption of herbicide-resistant crops likely led to increased use of weed killer, and that milkweed populations may have suffered as a result.
The argument seems logical, but it’s not iron-clad proof—correlation does not prove causation, and there don’t appear to be any controlled experiments that compare milkweed growth rates near Roundup Ready crops versus non-GM crops. Even assuming that modern, GM-using farming techniques are responsible—indirectly—for an increased decline in monarch butterflies, it’s still not the same as GM crops killing the insects outright.
Bottom line: It’s the farmers that are responsible, not the technology they’re using. Milkweed is after all a weed, and since weeds decrease yield, farmers always have and always will fight them. Most of the world is fed via conventional farming whose aim is to maximize efficiency and output. It’s unfortunate, but there really isn’t much room for biodiversity in conventional farming, especially for plants without a clear economic value like milkweed.
Some have proposed that we could protect milkweed plants, or that biotech companies could engineer a Roundup-resistant milkweed variety. A New York Times article from 2011 suggests that it is “unrealistic to expect farmers to give up the herbicide-tolerant crops — so efforts should be made to preserve or grow milkweed elsewhere, perhaps on farmland set aside for conservation.” Monarch Watch, an organization dedicated to studying and protecting the butterflies, says people can help by creating monarch habitats in home gardens, at schools, businesses, parks, along roadsides, and on other unused plots of land.
Grist’s article may exploit the specter of Big Bad agriculture, but it gets one thing right: “at this rate, if we’re going to save monarchs, we may need to make it a national priority to cultivate milkweed outside of farms.”