The Importance of Shifting Disturbance Regimes in Monarch Butterfly Decline and Recovery

The Eastern migratory monarch butterfly has declined in recent decades, partly because widespread adoption of herbicide-resistant corn and soybean has nearly eliminated common milkweed from crop fields in the US Midwest. We argue that in addition to milkweed loss, monarch declines were likely exacerbated by shifting disturbance regimes within their summer breeding range. Monarchs prefer to lay eggs on younger, vegetative milkweed stems. They...