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The Relativity of Weeds

A distressing column about dramatic reductions in the population of monarch butterflies ran on the front page of the Des Moines Register recently (August 29, 2014). Among other things, the story reported a steady decline over the last two decades in the number of monarchs observed in one of the principal sites in Michoacán to which monarchs from the United States migrate for the winter. In 1996, the overwintering butterflies covered 45 acres in this location, whereas last year they covered only 1.7 acres. This and other evidence of falling numbers prompted Lincoln Brower, a leading monarch researcher from Sweet Briar College in Virginia, to join with several conservation organizations in petitioning the U.S. Fish and Wildlife Service to extend to monarchs threatened species status under the Endangered Species Act. Brower believes that an important contributor to the monarch’s decline is a decline in the availability of the only food monarch larvae eat: milkweed. Iowa is home to 17 species of milkweeds, although five of them are on the state threatened/endangered species list. In the Grinnell area, four species are commonly found in natural and reconstructed prairies and wetlands (common, butterfly, whorled, and swamp). Butterfly, common, and swamp milkweed are the most favored by monarchs. Why the decline in milkweed? Brower attributes it to the widespread use of the herbicide Roundup throughout the midwestern corn belt, and he cautions that monarchs could be “a canary in the coal mine” warning us of even more serious environmental problems. Our name milkweed immediately categorizes the plant as an undesirable. By comparison, the Lakota and Dakota name for one of the milkweeds, waxca-xca, means “flower blossom,” and those groups traditionally used the milkweed flowers for food. The Omaha and Ponca tribes’ word for another of the milkweeds is makan saka, meaning “raw medicine,” for they traditionally ate the root to relieve bronchial and pulmonary problems. To monarch larvae, far from being a weed the milkweed plant is life itself.