New York Times
: Every year millions, perhaps billions, of Monarchs fly from their summer homes in the US and Canada to winter in Mexico. Over the past several years, however, their numbers have been decreasing dramatically, due to loss of habitat and extreme weather events. According to the World Wildlife Fund and the Mexican government, this year’s Monarch population covers just 1.65 acres of pine and fir forests in Mexico, compared with nearly 45 acres 20 years ago. The main problem is the loss of the Monarchs’ major food source, milkweed, to the growing of corn and soybean crops by farmers in the US Great Plains. And record-breaking hot and cold spells over the past several years have also affected the butterflies' migration. Although the Monarchs are not in immediate danger of extinction, butterfly researchers hope that the potential loss of what has been called one of the world’s great natural spectacles may spur action to protect the wide variety of beneficial insects, including the Monarch, that are disappearing.