Milkweed image via Liz West/Flickr. Creative Commons License 2.0.

I’m here to tell you about a weapon that could change the world. It’s small, inexpensive, and easy to conceal. Discharging it in public wouldn’t harm any living creature; it wouldn’t even land you in jail. What it would do, believe it or not, is save millions of lives.

Butterfly lives.

Brothers and sisters, I speak of the milkweed seed bomb: a golf-ball-size grenade of dirt, clay and seeds that might just help salvage one of the most magnificent—and, in recent years, most endangered—wildlife migrations on Earth. Each year, millions of monarchs embark on a trek that spans the length of an entire continent, from Mexico to Canada—a distance of 2,400 miles. On the way north, the monarch population cycles through four generations. Going south, a single “supergeneration” makes the long trip.

But for the last two decades, fewer and fewer monarchs have been making it to their wintering grounds in the fir forests of Mexico’s Sierra Madre Mountains. Sure, the number of butterflies—33 million—that currently migrate south sounds like a lot. But the fluttering horde was at least one billion strong as recently as 1997.

Monarch butterflies image via Felix’s Endless Journey. Creative Commons 2.0 license.

Many scientists have theorized that deforestation is at the root of the population’s decline: as loggers have continued to remove trees from the Sierra Madres, cooler air has swept into the forests and killed the insects, which are sensitive enough to cold temperatures that they huddle together in great masses to conserve warmth. Other scientists blame agricultural pesticides in the United States and Canada that the monarchs encounter on their journey. Still other evidence seems to point the finger at extreme weather events as the main reason that so many butterflies are a no-show in Mexico.

But a recent study, published last month in the Journal of Animal Ecology, suggests a far simpler solution to this mysterious problem: We need more milkweed. Lots more milkweed. “Monarchs depend on milkweed plants,” says Tyler Flockhart, the study’s lead author and a conservation biologist at the University of Guelph. “Milkweed plants are declining. And that’s the main cause of monarch population declines.”

Flockhart and his coauthors have developed a sophisticated model that allows them to estimate the effects of habitat loss across the monarch’s entire range—from the butterfly’s wintering grounds in Mexico to its breeding grounds in the United States and Canada. But you don’t need to worry, as they do, about “stochastic and density-dependent periodic projection matrix models” to appreciate the importance of their findings.

You just need to worry about milkweed. It’s “the only plant monarchs lay their eggs on,” says Flockhart. “And it’s the only plant they’ll feed on as larva before they develop into butterflies.” Put very simply: As the milkweed goes, so do the monarchs.

“Milkweed,” by the way, is not a single species of plant, but rather a sizeable group of plants—73 species of which are native to North America. It’s capable of growing across a wide variety of habitats and conditions, but as our landscapes fill up with ever more suburbs and cities, fewer patches of wild land exist for milkweed—resilient though it may be—to hang its white, wispy hat.

Not helping matters at all are crops that have been genetically modified to resist pesticides, or “RoundUp-ready.” Such crops allow farmers to apply even more of the herbicide glyphosate (sold commercially under the name “RoundUp”) to their fields, causing huge swaths of land—especially in the “Breadbasket” of the Midwest—to become lethal to milkweed plants. When migrating monarchs stop off in these fields during an egg-laying layover, there’s nothing there for them to lay their eggs on.

Caterpillar image via Douglas Mills/flickr. Creative Commons 2.0.

For its part, the Natural Resources Defense Council (which publishes OnEarth) filed a petition earlier this year asking the Environmental Protection Agency to complete a new review of glyphosates, something the agency hasn’t done since 1993. According to Rebecca Riley, an NRDC attorney specializing in wildlife issues, a new evaluation of the herbicide is necessary, since farmers—thanks to RoundUp-ready crops—apply much more glyphosate on their land than they did two decades ago. Among other things, Riley suggests that the EPA should restrict the use of glyphosate on roadsides, create and enforce buffer zones around farms to prevent runoff, and set aside land for milkweed cultivation.

Those are all great suggestions, every one of them. But why wait around on slow federal machinery when you’ve got a milkweed bomb burning a hole in your pocket?

“The whole basis of the monarch’s occurrence in North America is based on the migration, and the fact that there’s supposed to be milkweed all over the place,” says Andy Warren, a lepidopterist and collections manager at the McGuire Center for Lepidoptera & Biodiversity. “So, really, anything anybody can do to put more milkweed out there is good.”

Cue the bombs.

So-called guerrilla gardeners have been launching seed bombs into vacant or dilapidated urban lots for years. Building them is easy: make a tiny mud pie out of dirt, clay, and milkweed seed—making sure to use only seeds that are native to your area and that haven’t been treated with any kind of pesticide. Then just play a little game of patty-cake to shape the pies into projectiles, let them dry for a bit in the sun, and lob the mud globs onto any patch of land that makes sense. (Highway medians, ditches, and gravel patches beside railroad tracks are all good candidates. Private office parks, secure facilities, and your neighbors’ flower garden are not.)

In short, it’s time to get creative. That’s what Jenny Kendler, a Chicago-based artist (and monarch maven) has done. At the end of July, Kendler plans to hand out fully biodegradable balloons, pre-filled with fluffy milkweed seeds, to passersby in St. Louis. (Why St. Louis? Maybe it has something to do with the fact that a certain glysophate-inventing multinational is headquartered there.)

Upon receipt of a balloon, Kendler will be encouraging St. Louisians to pop it in a suitable location that’s near and dear to them, personally—releasing the milkweed seeds to the wind.

Milkweed image via yeimaya