Migrating Monarch Butterflies Might Actually Take to the Highway

Threatened pollinators get a trans-continental right of way

A monarch feasting on milkweed. (Bark)
smithsonian.com

The Monarch butterfly population has been in decline, but the North American insects are getting some unlikely help with their migration.

This month, a Pollinator Health Task Force, formed at President Obama's request and including government agencies from the Federal Highway Association to Fish and Wildlife as well as non-governmental partners, released a plan to protect pollinator habitat and curb pollution from pesticides. The "National Strategy to Promote the Health of Honey Bees and Other Pollinators" calls for research into why pollinator populations are declining, public education, increasing and improving habitat, and forming public-private partnerships to execute these goals. But the plan also mandates some interesting infrastructure plans.

“Many of the priority projects will focus on the I-35 corridor from Texas to Minnesota that provides spring and summer breeding habitats in the monarch’s key migration corridor,” the plan says. Monarch butterflies, which are crucial pollinators, migrate 1,500 miles, from central Mexico to Canada, every year and need stopover sites, with food and shelter, along their way. I-35, which runs from Laredo, Texas to Duluth, Minnesota, is the heart of their eastern migration path. By making the space on either side of the highway hospitable to monarchs, the government group is hoping to bolster the butterfly population up to 225 million by 2020.

Pollinators, which also include bees, bugs and birds, are struggling. Last year, beekeepers in the U.S. lost almost half of their honeybees, and over the past 20 years, the North American monarch population has been decimated, dropping from 1 billion to less than 60 million, mainly due to loss of habitat and pollution from herbicides and pesticides. The decline is particularly scary, because pollinators are not just important for biodiversity. Honey bees alone add $18 billion to the agricultural sector each year. If pollinators don’t survive, we don’t eat.

A highway, with its constant noise and air pollution, might seem like an unlikely habitat for a sensitive species. But, because the road is already there and contiguous, it makes sense for a right-of-way. According to the report, highways “are generally maintained in sunny areas with low vegetation height (ideal pollinator habitat), and often extend for considerable distances, thereby potentially acting as corridors for species movement and adaptation to climate change.” Plus, the government already owns the interstate land, and it is in a powerful position to work with adjacent landowners, farmers and non-profit groups to restore habitat.

The National Wildlife Foundation is spearheading the effort, along with the Fish and Wildlife Service. They’ve collectively kicked in $3.2 million dollars, and they’re working with partners, including state transportation departments. The first step to making the corridor more habitable is seeding. They’re going to put in plants that monarchs depend on, such as milkweek, along the roadways. Sprinkling seeds might seem trivial, but loss of food supply, which has happened in a lot of places due to large-scale farming, has had a huge impact on the butterflies. “The decline of monarchs is related to this loss of milkweed,” says U.S. Fish and Wildlife director Dan Ashe.

The monarch's migraton path—and I-35—runs through the heart of the corn belt, and a wide stretch of former tall grass prairie that's now predominantly farm land. That's a double whammy for the butterflies. In addition to losing habitat, they're impacted by pesticides and herbicides. The next step in the federal policy is a change in pesticide use and a more integrated pest management plan. As part of the strategy, the task force released a "Pollinator-Friendly Best Management Practices for Federal Lands" report. It covers a range of management techniques, from thinning roadside forests to using other species for pest control. They're hoping to set a standard for public land that can then be used on private land.

Migration corridors are crucial for the survival of animal groups that move, but they can be hard to find, because a single break in the pathway can have a big impact. The National Wildlife Foundation has worked to set aside similar corridors for wolves, caribou and other migrating animals. The butterfly pathway is easier in some ways, because flying animals aren't deterred by a fence line or a roadway.

There’s been some blowback from conservation groups and scientists, like University of Hawaii entomologist Daniel Rubinoff, that the monarch is getting more attention that it deserves, and that a fraction of the funds dedicated to butterflies could be put to better use targeting other species, like the Mariana wandering butterfly. On the other side, butterfly advocacy groups say habitat creation isn’t enough, and that the monarchs should be put on the endangered species list. The Xerces Society, an insect conservation non-profit that focuses on monarchs, says the new strategy doesn't do enough to protect pollinators from specific pesticides. They worry about systemic insecticides, like neonicotinoids, which can damage the central nervous systems of insects. “The national strategy includes valuable long-term plans that could, over time, strengthen the pesticide regulatory system,” said Aimee Code, pesticide program coordinator for the Xerces Society, in a press release. “But, it fails to offer pesticide mitigations to address issues currently facing pollinators.”

But so far, most of the response to the report has been positive. Minnesota Senator Amy Klobuchar, who has been a vocal supporter of the effort, is excited about those groups that have come on board. "I am pleased to see the Fish and Wildlife Service taking positive steps to reverse its [the monarch's] decline. But we all must do more," she says. "It will take all hands on deck to protect the butterfly from extinction."

About Heather Hansman
Heather Hansman

Heather Hansman is a Seattle-based freelancer who writes about science, the environment, tech and people, and how they all interact. Her work has appeared in Outside, Popular Science and Grist.

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