Falling Reign: Drought, Industrial Ag Precipitate Disastrous Decline of Monarch Butterflies

These Monarch butterflies are wintering in Michoacán, Mexico, after long sojourns from Canada and the midwestern U.S. They are the only insect known to undertake such marathon migrations. - Photo by Pablo LeautaudThe monarch butterfly population is crashing. Over a 50-acre swatch of central Mexico each winter, monarch butterflies once formed a living blanket over the trees. They now occupy less than three of those acres. Last winter’s butterfly numbers in Mexico were down 59 percent from the year before.

The butterflies’ doom appears linked to weather and agricultural practices in the midwestern United States, where the monarchs congregate in the summer to reproduce. Drought and hot weather has led the butterflies to arrive early and to nest farther north. Chip Taylor, director of the conservation group Monarch Watch, told the New York Times that this has disrupted the breeding cycle, dried insect eggs, and lowered the nectar content of the milkweed on which they feed—or what little remains of it. The second problem is that where once monarchs found plentiful milkweed growing between rows of corn and soybean, farms now plant herbicide-tolerant crops and wipe out the monarch’s food supply. Taylor told the Times “‘That habitat is virtually gone. We’ve lost well over 120 million acres, and probably closer to 150 million acres.’”