If the North American continent had an official insect, it might well be the iconic, majestic monarch butterfly. Millions upon millions of the orange-and-black insects move between Canada, the United States and Mexico in an epic and mind-boggling multigenerational migration. California has a special place as a winter home to enormous clusters along the southern and central coasts.
But monarchs are in danger. Their population has been sharply declining over the past 20 years, and environmental advocates think they know why: the widespread use of an herbicide called glyphosate, more commonly known by the brand name Roundup.
The Natural Resources Defense Council last week filed a petition with the Environmental Protection Agency asking for new restrictions on glyphosates.
The chemical was approved for use in 1993 and has become ubiquitous, including "Roundup-ready" farming — crops that are genetically engineered to withstand the herbicide — and home landscaping.
Sylvia Fallon, a biologist and director of the NRDC's Wildlife Conservation Project, says that the group is not seeking a ban, just limits on the use of glyphosates next to highways and public easements where weeds like to grow, and in areas around crops.
It's a reasonable request considering the herbicide's apparent effect on monarchs. It's not glyphosate itself that is the problem, Fallon says. The problem is that the herbicide is so effectively killing the plant that monarchs depend on for survival — milkweed.
This unlovely, hardy plant is the main food for monarch larvae and is where the butterflies lay their eggs. But since the widespread adoption of glyphosates in agriculture, the amount of milkweed has plummeted.
Scientists John Pleasants and Karen Oberhauser have found that between 1999 and 2010, milkweed in the Midwest declined by nearly 60%. Meanwhile, the population of monarchs declined by more than 80%.
Observations in Mexico are more alarming. Before 1993, an estimated 1 billion monarchs migrated across North America to Mexico each year. Last year, only about 35 million showed up.
If a world without monarch butterflies isn't reason enough, consider the bigger concerns about environmental degradation and the stress on the all-important pollinators.
Government agencies work slowly. But backyard gardeners certainly can help by going easy on the application of weed killer this spring or even planting milkweed to attract monarchs. And everyone can push local and state agencies to limit their use of weed killers on public land.
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