The population of Monarch butterflies declined sharply this year. In Iowa, they have seldom been seen, even among people who preserve their milkweed plants for the orange and black insects to feed and reproduce. According to official counts, the population declined by as much as eighty percent in Mexico this winter.
During a recent interview, Orley Taylor— founder and director of Monarch Watch, a conservation and outreach program— talked about the factors that have led to the sharp drop in the monarch population. Among them, Taylor said, is the increased planting of genetically modified corn in the U.S. Midwest, which has led to greater use of herbicides, which in turn kills the milkweed that is a prime food source for the butterflies.
“What we’re seeing here in the United States,” he said, “is a very precipitous decline of monarchs that’s coincident with the adoption of Roundup-ready corn and soybeans.”
There isn’t a clear answer to why Monarch butterflies are in decline. There are concerns that the lower population makes survival of the species, and its ability to rebound to previous numbers tenuous. If you’d like to read more, here are some useful articles:
Why Monarch Butterflies’ Numbers are in Freefall by Vidya Kowri.
The Monarch Butterfly Decline, and What You Can Do About It by Matt Miller.
Tracking the Causes of Sharp Decline of the Monarch Butterfly by Richard Conniff.