Gardeners' Good Intentions Are Killing Monarch Butterflies 

For monarch butterflies, the path to endangered species status could be pave with good intentions.

Throughout the United States, monarch-lovers are replenishing the supply of milkweed — the plants monarchs lay their eggs in — by growing it in their gardens. However, they’re planting the wrong species of milkweed. And in doing so, well-intentioned gardeners are actually putting more stress on declining monarch populations by convincing them to give up the annual migration altogether.

 

Every year, millions of monarchs migrate from their summer breeding grounds in the eastern U.S. and Canada to wait out the winter in central Mexico. However, since the 1990s, monarch numbers have declined by nearly 90 percent. Humans, with all our farm fields, roads and buildings, are largely to blame for the monarch’s decline. Deforestation has decimated the monarch’s preferred habitats both north and south. And herbicide-resistant crops allow farmers to spray stronger weedkillers on their fields, which kills native milkweed in the process.

 

To counteract the loss of milkweed on farm fields, sympathetic gardeners in southern states are giving monarchs a meal by planting milkweed in their backyards. Unfortunately, the milkweed they’re planting is an exotic tropical species called  Asclepias curassavica that grows year-round, unlike the native species, Asclepias incarnata, that dies off seasonally. So, rather than fly south for the winter when the milkweed dies off, monarchs are forgoing the Mexico migration, living and breeding year-round in the south. And that’s trouble