Climate Change Threatens Monarchs
New research suggests that climate change could severely disrupt the mass migration of monarch butterflies. Scientists warn that the habitat for the milkweed plant, which is crucial for monarchs, is shifting southward in Mexico. This habitat fragmentation threatens to fracture established migratory routes and could push some populations to the brink.
The eastern monarch population, which travels from the northern U.S. and Canada to central Mexico, has plummeted by about 85% since the mid-1990s. A separate western population, migrating to the California coast, is also at risk. The monarch is the only butterfly known to make a two-way migration, with some individuals flying as far as 3,000 miles. Beyond climate change, the widespread use of herbicides is a primary driver of milkweed loss. Crops genetically modified to resist glyphosate, the active ingredient in Roundup, have allowed for broad application of the herbicide, killing milkweed that once thrived in and around agricultural fields. This plant is the only food source for monarch caterpillars. Rising temperatures can also directly harm the butterflies. Warmer conditions can cause milkweed to produce higher levels of a toxic chemical called cardenolide, potentially poisoning the caterpillars that feed on it. Additionally, warmer and drier conditions can reduce the abundance of nectar-producing plants that adult monarchs rely on for fuel during their long migration. The monarch is now listed as endangered under Canada's Species at Risk Act. In the United States, the Fish and Wildlife Service has proposed listing the monarch as a threatened species under the Endangered Species Act. The International Union for the Conservation of Nature (IUCN) classifies the migratory monarch as vulnerable. Conservation efforts are underway to restore monarch habitats. Organizations like the National Wildlife Federation are engaging communities and mayors to plant native milkweed and other nectar-rich wildflowers in gardens, schoolyards, and public spaces. The Natural Resources Conservation Service also works with farmers and ranchers to create and manage habitats on private lands.
