Can an Interstate Bug Highway Save the Monarch Butterflies?

Image by Tiago J. G. Fernandes via Wikimedia Commons

Every year, monarch butterflies take on an astounding multi-generational migration, traveling thousands of miles from Canada and the Northern United States to the South and Mexico. Like humans on a mission to colonize Mars, these brave little insects are undertaking a one-way journey; when they reach their destination they will lay eggs and die, leaving their offspring to complete the round trip without them.

Nobody’s quite figured out how the butterflies know to follow the same familiar route year after year. But their annual return is a brilliant, breathtaking phenomenon—photographer Joe Sartore described the scene on CBS News earlier this year:

There, standing silently in the mist, were ancient fir trees so laden with Monarch butterflies their bows literally bent under the weight. Can you even imagine how many butterflies it takes to make a tree branch sag?

When the sun finally came up, millions of brilliant orange spots burst from the trees, rising and falling and swirling around me like a great living blizzard.

Wintering monarchs. Image by Agunther via Wikimedia Commons

Over the last two decades, though, the milkweed plants the monarchs use as food and spawning grounds have been increasingly devastated by pesticides from farming operations, depleting resources for the butterflies. The U.S. Fish and Wildlife Service estimates that since 1990, nearly a billion monarchs have disappeared as a result of this milkweed loss and other habitat degradation. Now, by way of a recently unveiled national strategy, the government is fighting back against the die-off by creating a “butterfly corridor” of monarch-welcoming land that will stretch from Minnesota to Mexico, mostly along U.S. Interstate Highway 35.

The plan, which also addresses the welfare of bees and other vital pollinators, will designate a path of around 1,500 miles in which the butterflies’ migratory needs are ensured. As Scott Hoffman Black, executive director at the Xerces Society for Invertebrate Conservation told Public Radio International: “Patches of high-quality habitat that's rich in flowers and free of pesticides forming a corridor from Mexico to Canada will help monarchs to find nectaring and breeding areas as they travel.”

Monarch caterpillar. Image by Sid Mosdell via Flickr

Using their unique access to passages such as I-35, the federal government will attempt to restore and protect around seven million acres of habitat along the route, as well as educate adjacent farmers and landowners about the issues threatening monarch populations. Sending bees and butterflies down an interstate’s gauntlet of cars and exhaust fumes might not sound like a plan for successful environmental rehabilitation. But the government’s report points out that the areas around the highway are actually “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.”

Aside from the larger goal of establishing the pollinator corridor, the project will put aside $3.2 million specifically for the needs of monarchs. The hope is that the butterflies’ populations will grow from the current number of about 50 million bugs to 225 million happy, flapping insects by 2020.