A stunning phenomenon is in danger of disappearing: The annual migration of millions of monarch butterflies from Canada and the US to Mexico every year has sunk to its lowest level on record and is in grave danger of dying out, researchers warn. This winter, the hibernating butterflies coat 1.65 acres of trees in a protected Mexican forest, down 44% from last year. The butterfly itself is not endangered, but the migration is under pressure from factors including climate change, deforestation, and changes to agriculture along the route, National Geographic finds.
"The main culprit" is now genetically modified "herbicide-resistant corn and soybean crops and herbicides in the USA," which lead "to the wholesale killing of the monarch's principal food plant, common milkweed," a leading entomologist tells the AP. To help the migration survive, researchers would like to see milkweed incorporated in plantings along areas like roadsides, and they urge gardeners to help by planting milkweed and making their gardens more butterfly-friendly. (Read more monarch butterflies stories.)