Lecture links monarch and butterfly declines to habitat loss and herbicide-tolerant crops

Wheelbacher explained that monarch butterflies require milkweed as a host for caterpillars and that modern midwestern cropping systems (Roundup-ready corn and soy) have eliminated the weedy margins monarchs historically used for breeding. He summarized monitoring that shows long-term declines in overwintering monarch colony area in Mexico and said public interest has spurred increased milkweed planting by homeowners.

He also cited a Xerces Society assessment that more than a quarter of North American bumblebee species face some degree of extinction risk and reported broader butterfly declines in the low single-digit percent per year that accumulate over decades.