Using milkweed to predict the future of the monarch

The monarch, perhaps the most familiar North American butterfly, relies exclusively on milkweed plants (Asclepias spp.) for food in its larval stages. This study investigates the effects of climate change on the host plants and, consequently, the butterfly. Combining climate projections with 24,000 occurrences, including records from the GBIF network, the study’s author modelled future distributions of milkweed and monarchs in the eastern United States, showing that optimal habitat for milkweed will shift north. What remains uncertain is whether monarchs will follow. Many factors, including genetics, control their migratory patterns, so this vegetation shift may present longer migration distances that could negatively impact the species.