WASHINGTON, April 25, 2016 – The American Soybean Association is touting a new study that finds a lack of nectar sources, habitat fragmentation, and changing weather patterns are the primary contributors to a decline in monarch butterfly populations.
The study by Cornell researchers found “problems in the butterflies’ migration from the U.S. and southern Canada to Mexico in the fall, rather than with lack of milkweed – the only food source for caterpillars in the summer,” the ASA said. Other theories have blamed the species’ decline on the widespread planting of genetically engineered crops and an increase in herbicide use.
“As we move into this crop season of 2016, let us be mindful as producers we can play a major role in maintaining and establishing monarch and pollinator habitat,” said ASA Director Wayne Fredericks, who represents ASA on the Monarch Collaborative, a group headed by the Keystone Policy Group that works to establish best practices for farmers and landowners to help conserve and recover populations of the important pollinator.
To help the monarch survive, he advised ASA members to “be aware of existing milkweed in your non-crop areas,” and cautioned against spraying those areas. “These milkweed are critical for the survival of this species. While this new study suggests monarchs are facing several challenges, we can do our part to ensure a sustainable population.”
A petition seeking listing of the butterfly under the Endangered Species Act blames the widespread planting of genetically engineered crops and an increase in herbicide use for the species’ decline.
But Anurag Agrawal, Cornell professor of ecology and evolutionary biology, said “lack of milkweed, the only host plant for monarch butterfly caterpillars, is unlikely to be driving the monarch’s population decline, as the problem appears to occur after they take flight in the fall.” Agrawal was the lead author on the paper published this month in Oikos, an online journal.
The butterflies migrate to Mexico for the winter. In the spring, new generations move through the southern U.S., ultimately reaching the Midwest and Eastern U.S.
“We find a sharp annual population decline in the first breeding generation in the southern USA, driven by the progressively smaller numbers of spring migrants from the overwintering grounds in Mexico,” an abstract of the paper says.
The latest news on monarch numbers was encouraging, as the forest area covered by the overwintering insect increased more than three-fold, to nearly 10 acres this past winter.
In a video posted on Cornell’s website, Agrawal said numbers decline during the monarchs’ fall migration, when they are feeding on water and nectar, contained in flowers such as goldenrod. “By the time they get to Mexico, their numbers are plummeting,” he said. “But at the end of the summer, when they start that migration, their numbers are not down.”
“It would be a mistake to think that planting milkweed alone is going to solve this problem,” he said.
After making a positive finding on a listing petition on Dec. 31, 2014, the U.S. Fish and Wildlife Service was supposed to decide by the end of 2015 whether to propose the butterfly as threatened or endangered under the Endangered Species Act. The deadline passed without a decision, however, leading two of the petitioners, the Center for Biological Diversity (CBD) and Center for Food Safety, to sue the agency last month.
The petition asserts that widespread planting of genetically engineered crops in the Midwest has led to the monarch’s decline. “The dramatic surge in Roundup use and ‘Roundup Ready’ crops has virtually wiped out milkweed plants in Midwestern corn and soybean fields,” CBD said in a March 10 news release. “It is estimated that in the past 20 years these once-common 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 petitioners do not say that GE crops are the only factor involved in monarch population losses. They also cite “global climate change, drought and heat waves, other pesticides, disease and predation, urban sprawl and logging on their Mexican wintering grounds.”
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