Monarchs butterflies’ decline correlated to increased plantings of herbicide tolerant GM crops and overuse of glyphosate (RoundUp) herbicide.
Twelve years ago, a study found that genetically modified Bt corn was lethal to monarch butterflies; recent research shows that another type of GM crop is even more damaging to the beloved insect.
“What’s going on down there is a disaster”
A recently published study says that increasing acreage of GM Roundup Ready (RR) corn and soybeans is a major cause for declining populations of monarch butterflies in North America. The paper, published in the journal Insect Conservation and Diversity, says that increased use of glyphosate herbicide with RR GM crops in the Midwest is killing milkweed plants, which monarchs rely on for habitat and food.
Chip Taylor, an insect ecologist at the University of Kansas and co-author of the paper, told the New York Times, “This milkweed has disappeared from at least 100 million acres of these row crops. Your milkweed is virtually gone.”
The paper documents that populations of monarch butterflies in central Mexico, where they migrate to in winter, have declined over the past 17 years, reaching an all-time low in 2009-2010.
Lincoln P. Brower, an entomologist at Sweet Briar College and co-author of the paper, told Wired magazine: “What is going on on the ground down there is a disaster.”
Monarch butterflies migrate from the United States to Mexico each year, traveling some 4000 miles.
Taylor and Brower both criticized a recent paper by Andrew K. Davis, an assistant research scientist at the University of Georgia, which didn’t find a significant decline in monarch populations. Davis analyzed monarch populations in Cape May, N.J., and Peninsula Point, Michigan. Brower said those are minor sites that would not reflect the true status of monarch populations. “His paper is not representative of the big picture (of overall monarch populations), which is Mexico.”
“Bigger threat than Bt corn”
While the paper lists several other factors, such as deforestation in Mexico, contributing to declining monarch populations, Taylor says the proliferation of RR crops and the overuse of glyphosate is the major cause.
“This is the one main factor that has happened,” he says. “You look at parts of the Midwest where there is a tremendous use of these crops and you see monarch populations dropping. It’s hard to deny the conclusion.”
Taylor has been warning about the negative impact of RR crops on monarchs since writing a blog about it in 2001. “I’ve always thought they were a bigger threat to monarchs than Bt corn.”
Taylor says the monarchs’ decline accelerated around 2003 when herbicide tolerant GM crops accounted for nearly 50% of all corn and soybeans. That number has increased to more than 80% in the last two years.
“Once herbicide tolerant GM crops reached 50%, we saw a significant impact on monarch populations,” he says.
RoundUp/glyphosate: “Biodiversity Armageddon”
The amount of glyphosate herbicide used by US farmers has exploded. In 2007, as much as 185 million pounds of glyphosate was used, double the amount used in 2001, and five times as much as in 1997.
Recent studies have documented many negative impacts of glyphosate including malformations and birth defects in animals, cancer, genetic damage, endocrine disruption, and other serious effects, often at very low doses.
“It kills everything. It’s biodiversity Armageddon,” says Brower.
Taylor, Brower, and the paper’s other authors state, “We conclude that, because of the extensive use of glyphosate herbicide on crops that are genetically modified to resist the herbicide, milkweeds will disappear almost completely from croplands.”
“Biotech companies mislead the public”
Milkweed’s disappearance has also been documented by Robert Hartzler, an agronomist at Iowa State University, who found that the plant’s presence in Iowa’s corn and soybean fields has plunged 90% from 1999 to 2009. Hartzler also says that glyphosate has contributed to milkweed’s decline.
Taylor says more research will be published documenting glyphosate’s role in decimating monarch butterfly populations. “There are other papers in the works that will verify the decline and the association with the adoption of herbicide tolerant crops.”
Taylor, who heads Monarch Watch, a group dedicated to conserving monarchs, says that efforts should focus on preserving milkweed by encouraging individuals to introduce the plant into home gardens and reintroducing it wherever it has been eradicated.
Brower recommends that roadsides in the US be protected from pesticide spraying and that more conservation areas are set aside to maintain native plants.
Brower says most Americans aren’t aware of the devastation to biodiversity caused by GM crops.
“It’s atrocious what’s going on, and it’s very easy for the biotechnology companies like Monsanto to propagandize and mislead the public.”
Bt corn deadly to Monarch butterflies
This is the second time that GM crops have been shown to harm monarch butterflies. In 1999, Cornell entomologist John Losey published a paper showing that pollen from GM Bt corn was lethal to monarch butterfly larvae. A later study conducted at Iowa State University also showed monarch larvae dying after eating milkweed leaves containing Bt pollen in field conditions.
The biotechnology industry responded by funding a series studies showing – not surprisingly – that Bt corn presented a negligible risk to monarchs. However, several scientists including Brower, Losey, and Iowa State University researcher, John Obrycki, wrote letters to the Environmental Protection Agency, citing weaknesses in the studies. Brower said that toxicology experiments were not done under natural field conditions. Losey and Obrycki said the studies were based on the assumption that monarchs consume only pollen and not other corn tissue, such as anthers, which contain high concentrations of Bt toxins.