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Monarch butterfly sipping nectar from milkweed. Photo: Sherri VandenAkker via Flickr (CC BY-NC-SA).
Monarch butterfly sipping nectar from milkweed. Photo: Sherri VandenAkker via Flickr (CC BY-NC-SA).
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Monarch butterflies down over a quarter in one year

The Ecologist

10th February 2017

It's been another disastrous year for North America's Monarch butterflies, with the insect's population down 27% in a single year. The sudden decline is blamed on severe winter storms in Mexico, and the impacts of GMO crops, herbicides and insecticides on US farms.

In addition to threats from more frequent and harsher weather events, monarchs are still severely jeopardized by the ever-increasing pesticides used with genetically-engineered crops destroying their habitat.

The annual overwintering count of monarch butterflies released today confirms butterfly numbers fell by over a quarter from last year's count.

Scientists report that this year's population is down by 27% from last year's count, and down by more than 80% from the mid-1990s.

This dramatic decline indicates that America's most well-known butterfly is at ongoing risk of extinction.

This year's drastic decline is attributed in part to extreme winter storms that killed millions of monarchs last March in Mexico's mountain forests where 99% of the world's monarchs migrate for the winter.

"The monarch butterfly is still in really big trouble and still needs really big help if we are going to save this beloved orange and black wonder for future generations", said Tierra Curry, a senior scientist at the Center for Biological Diversity.

A recent study by the US Geological Survey concluded that there is a substantial probability that monarch butterflies east of the Rockies could decline to such low levels that they face extinction. Researchers estimate the probability that the monarch migration could collapse within the next 20 years is between 11% and 57%.

GMO crops and herbicides another driver of decline

The butterfly's dramatic decline has been driven in large part by the widespread planting of genetically engineered crops. The vast majority of US corn and soybeans are genetically engineered for resistance to Monsanto's Roundup herbicide, a potent killer of milkweed, the monarch caterpillar's only food.

The dramatic surge in the use of Roundup and other herbicides with the same active ingredient (glyphosate) on Roundup Ready crops has virtually wiped out milkweed plants in Midwest corn and soybean fields.

Another risk comes from GMO crops engineered to express naturally occuring insecticides from Bacillus Thiringuensis (Bt) bacteria. The crops can express the toxin at levels that kill or harm Monarch and other butterfly caterpillars. They are also susceptible to the now widely used neonicotinoid insecticides, which can contaminate the nectar from treated crops.

"In addition to threats from more frequent and harsher weather events, monarchs are still severely jeopardized by the ever-increasing pesticides used with genetically-engineered crops destroying their habitat", said George Kimbrell, senior attorney for Center for Food Safety. "We will continue to do everything we can to ensure monarchs have a future."

In the past 20 years it is estimated that these once-common, iconic orange and black butterflies may have lost more than 165 million acres of habitat - an area about the size of Texas - including nearly a third of their summer breeding grounds.

The way of the Passenger pigeon?

Found throughout the United States during summer months, most monarchs from east of the Rockies winter in the mountains of central Mexico, where they form tight clusters on trees. Scientists from World Wildlife Fund Mexico estimate the population size by counting the number of hectares of trees covered by monarchs.

Monarchs need a very large population size to be resilient to threats from severe weather events, pesticides, climate change, disease and predation. A single winter storm in 2002 killed an estimated 500 million monarchs, roughly five times the size of the current population.

Logging on the monarch's Mexican wintering grounds is also an ongoing concern. Scientists have also identified threats to the monarch during the fall migration including lack of nectaring habitat and insecticides.

Concerns over the extinction risk of the monarch led the Center for Biological Diversity, the Center for Food Safety, the Xerces Society and renowned monarch scientist Dr. Lincoln Brower to petition the US Fish and Wildlife Service in 2014 to protect the butterfly as threatened under the Endangered Species Act.

The Service is now conducting a review of its status and must decide on protection by 2019.

In Canada, the Committee on the Status of Endangered Wildlife has recommended that the Canadian government list the monarch as an endangered species. Monarch butterfly migration is now recognized as a 'threatened phenomenon' by the International Union for the Conservation of Nature.

 


 

Principal source: Center for Food Safety (CFS).

CFS's mission is to empower people, support farmers, and protect the earth from the harmful impacts of industrial agriculture. Please join our more than 800,000 consumer and farmer advocates across the US. Twitter: @CFSTrueFood, @CFS_Press

The Center for Biological Diversity is a national, nonprofit conservation organization with more than 1.1 million members and online activists dedicated to the protection of endangered species and wild places.  See website.

 

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