As the first wave of an amazing multigenerational migration of monarchs arrives in Mexico this month for winter, scientists are finding every link in their complex life cycle is under threat.
Already facing natural high mortality during migration from causes that can range from predators, including birds, mice, insects and parasites, to the risk of getting drenched in rain when temperatures drop, the monarch now struggles against its greatest threat: the consequences of human behavior. Luckily, conservationists have discovered how we can help offset the threat.
The number of monarch butterflies has steadily dropped around 80 percent, or more by some estimates, in the past 15 years, barely recovering from the lowest plummet in 2009-2010.
Summer’s last generation of monarchs follow ancient routes southward, riding air currents and soaring like birds across thousands of miles. They seek small specific sites in California and in Mexico’s high altitudes where forests offer shelter under fir trees that provide the warmth they need. Last year, the lowest colony size ever was reported in Mexico.
Ernest Williams, a professor of biology at Hamilton College, told the New York Times that the forests the monarchs rely on in Mexico are being illegally logged and are changing as a result of climate change, which is having a negative impact on the butterfly’s population. He also found that today’s ecotourism inviting visitors to witness their massive gathering is disturbing the fragile plight of the butterflies.
In spring their congregations migrate north in search of milkweed plants, the only plant that monarchs lay eggs on and caterpillars eat, in the midwest and northeast. Using visual and chemical cues to find the plant, the sensory nerves on their feet and heads help them choose the best quality of milkweed. A female lays one egg at a time and can lay many in a single day. The survival of the larvae depends critically on the milkweed.
Milkweed grows along edges of forests and in open spaces. Unfortunately, the plant is being destroyed by the herbicide glyphosate, which is sprayed on fields where genetically modified Roundup-ready corn and soy crops are grown. As the milkweed disappears, the monarchs vanish with it.
Towns and counties have been encouraged to let the plants thrive along roadsides. Gardeners and landowners are encouraged to re-establish native species, plant milkweed in their yards and allow a space for them to grow with grasses and native flowers along woods edges and around crop fields where they enrich the soil and hold off erosion.
The good news for monarchs is that we love them and are willing to spend a lot to support conservation efforts, according to a new study published in the journal Conservation Letters. As part of the study, experts from the U.S. Geological Survey (USGS), Colorado State University and the University of Minnesota surveyed households to see what they would be willing to donate to animal protection organizations or spend on DIY gardening projects to help monarchs and found that we’re willing to give up to $6.64 billion to support conservation efforts.
The authors note that the National Gardening Association reported that gardeners spent $29.1 billion in 2012 alone.
“By reallocating some of those purchases to monarch-friendly plants, people would be able to contribute to the conservation of the species as well as maintain a flower garden,” lead author and USGS scientist Jay Diffendorfer said in a statement. “Helping restore the monarch’s natural habitat, and potentially the species’ abundance, is something that people can do at home by planting milkweed and other nectar plants.”
MonarchWatch, a conservation and outreach program, is urging people to get involved by planting and maintaining “waystations” to help monarchs along their migration by offsetting the losses of milkweed habitats. The organization offers seed kits and the opportunity to register sites with the International Monarch Waystation Registry.
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