From New Terrain, a newsletter of Ball Publishing: As many as 1.8 billion additional stems of milkweed plants in North America may return imperiled Monarch butterflies to a sustainable population size, according to a recently published U.S. Geological Survey (USGS) study. Habitat plants in the Monarch’s Midwestern flyway are most important.
“Milkweeds in corn and soybean fields produce more Monarch eggs than milkweeds located in non-agricultural areas,” Wayne Thogmartin, USGS Research Ecologist, said in a USGS press release.
“Competing demands for space in these agricultural locations limit the highly desirable habitat available to milkweeds and Monarchs.”
More than 860 million milkweeds were lost in the northern United States over the last decade. Scientists with the USGS and collaborators examined the density of Eastern migratory Monarch butterflies overwintering in Mexico from 1979-2002 and the amount of milkweed plants available to them in North America. The study found that 3.62 billion milkweeds are needed to reestablish the Monarch population, but only 1.34 billion remain in the U.S.