On Feb. 7, this year’s numbers from the annual Monarch Butterfly overwintering count in Mexico was released, and the news was more dire than expected.
The total forest area occupied by overwintering monarchs that make the epic 3,000-mile journey from Canada to Mexico dropped by 59.3% from the previous season, making it the second lowest number of monarch numbers counted to date.
A top reason monarch numbers are at a near all-time low, say experts, is due to drought conditions last fall throughout Oklahoma and into central Mexico. Not only has the drought conditions and other changing weather patterns reduced the flowering nectar production of wildflowers, it has affected the Monarch’s main food and egg-laying source – milkweed.
Oklahoma is one of the states that lie in the migratory path of Eastern monarch butterflies as they travel to overwinter spots in Mexico from Canada.
Chip Taylor, founding director of the nonprofit education, conservation, and research program Monarch Watch, and Kristen Baum, director of Monarch Watch, said the depth of this year’s decline is “beyond our experience, and the implications for the future of the monarch migration are surely of concern.”
“Droughts reduce flowering and therefore nectar production, and monarchs need the sugars in nectar to fuel the migration and to develop the fat reserves that get them through the winter,” said Taylor.
Both Western and Eastern have been declining for the last 20 years, said Dr. Emily Geest, a postdoctoral fellow overseeing a research project at the Oklahoma City Zoo to create a headstart program to protect the state’s rare milkweed populations. She said Oklahoma’s monarch butterfly population continues to decline due to climate change, habitat loss and pesticide use.
Other studies back up the growing concern about how climate change is affecting milkweed and pollinators that rely on the plant.
According to a fact sheet released by the Convention on the Conservation of Migratory Species of Wild Animals, higher temperatures also hinder the growth and quality of milkweed, and current predictions suggest the plant’s habitat will continue to shift to more favorable environments north or south.
Monarch butterflies may not be able to adapt to these changing sites and environments, CMS reports.
A new study published in the journal Ecology Letters found that as carbon dioxide levels rise in the atmosphere, strains of milkweed plants that help fight off parasitic infection lose their medicinal qualities.
“Our study shows that a loss of medicinal protection caused by elevated CO2 makes the parasite more virulent,” said lead author Leslie Decker, an ecologist at Stanford University.
To recover, Oklahoma will need an abundance of milkweeds and nectar sources. The Oklahoma City Zoo’s milkweed head start program, launched in Spring 2023, aims to do just that. In partnership with Oklahoma State University, The Nature Conservancy, Oklahoma State Parks, Oklahoma Department of Wildlife Conservation, US Army Corps of Engineers and USDA Forestry Service, zoo officials comb the state to find rare milkweed species, like the critically imperiled purple milkweed. They collect the seeds to germinate at the zoo lab and plan sites for future seedling reintroduction.
“The seedlings will hopefully do really well. We then plan to bring them back to where we collected them in April and also plant them in other parts of the state,” said Geest. “Our hope is to bolster that population of milkweed and make it a little bit more resilient to upcoming rain shifts and climate change.”