The Plight of the Monarch Butterfly
The Food Journal
April 16, 2015
The plight of nature’s pollinators links directly to our ability to produce food and fiber in an efficient and abundant way. A special pollinator is the iconic monarch butterfly – the king of butterflies.
These wonderful creatures go through four generations per year. Monarchs spend early spring in Texas and Oklahoma, returning to the upper Midwest toward the end of May and June. By September monarch butterflies are on their way to Mexico or California for the winter.
Monarchs east of the continental divide travel to Mexico – a journey of 3,000 miles. Most of those west of the divide travel to California. These are known as the Eastern and Western migratory populations of monarchs, but there is some movement between these two populations. Tagging studies have documented movement between Arizona and the Mexican wintering sites. Scientists still study their amazing migration seeking answers to why the fourth generation each year knows where to go to survive the winter.
Each individual monarch starts as an egg laid on milkweed. After about four days the eggs hatch and the small caterpillars are full grown in about 9-11 days. The caterpillars usually move off of their milkweed host plant to find a place to pupate, or change into a chrysalis that will undergo metamorphosis into the butterfly. That takes about 10 days. Each of the first three generations live about 2-6 weeks as adults, while individuals in the migratory generation live up to eight months.
Monarch butterflies are iconic and are noticed by everyone, urban, suburban, rural residents alike and all ages. Monarchs are frequently used in classrooms to illustrate insect life cycles, metamorphosis, migration, habitat characteristics and conservation.
Many caterpillars have very specific food sources. For monarchs it is milkweed. There are over 100 species of milkweed in North America. The sap of the milkweed is mildly poisonous. By eating and absorbing the mild poison the monarchs make themselves bitter tasting, and predators have learned to not eat them. A core problem is the disappearance of milkweed across our country leaving this species with limited options for each successive generation.
Although the debate continues, the use of pesticides and herbicides and the use of modern farming methods and biotechnology contribute to the decline of milkweeds. The decline of milkweed, in turn, contributes to the decline in the butterflies.
In 2000, several scientists, including Dr. Karen Oberhauser, University of Minnesota, Fisheries, Wildlife and Conservation Biology Department, did a study on milkweed presence in soybean and cornfields. Country-wide they found a significant amount of milkweed in agricultural fields, and they found that monarchs were using that milkweed. At that time, less than half of soybean fields and just a small fraction of cornfields were herbicide tolerant. Today, the adoption rate of herbicide tolerance is about 90 percent for corn and soybeans. What that means is that all of the milkweed that was in corn and soybean fields is gone. While some milkweed still grows in agricultural areas, the remaining milkweed mainly grows along roadsides and in some areas that have been planted for erosion control and wildlife.
“The study provided us with a baseline of how much milkweed was in the agricultural fields. When we did those calculations based on our 2000 data we estimated that the vast majority of monarchs came out of corn and soybean fields, because corn and soybean cover so much of the landscape in the upper Midwest. But that milkweed is virtually gone. Most people working on monarch conservation don’t think that it’s likely that milkweed within agricultural fields will come back, and thus we need to find alternative places on the landscape for monarch-friendly habitats,” says Oberhauser.
Producers of herbicide tolerant corn and soybean seeds are in the process of engaging different possible partners to see what they can do to get some milkweed back into the landscape – for example, planting milkweed on roadsides and CRP (Conservation Reserve Program) fields. Finding ways to enable advanced farming practices while increasing the habitat for species that are suffering habitat loss – like the monarchs – will be essential in the years to come.
“Monarch butterflies require milkweed for growth and development and nectar sources for adult sustenance. Monarch butterflies are good indicators of habitat that also benefits other wildlife species such as pollinators, birds, and other wildlife species. In restoring habitat for monarch butterflies we are providing a broader benefit for many wildlife species that are not as well known, but provide important benefits,” says Dr. Sue Blodgett, Chair of the Department of Entomology at Iowa State University and a member of The Iowa Monarch Conservation Consortium, an organization focused on a multi-faceted program with a goal of ensuring monarch butterflies remain a part of Iowa’s landscape.
Most experts report that monarch populations were as high as one billion in the mid-1990’s. Estimates for 2014 place the population at a record low of 34 million butterflies. Scientists fear that at that level, considering the challenges they face, the risk of extinction may be high. A single harsh winter can kill half the population. The population may not be able to withstand a brutal winter, drought or other challenges that higher numbers would enable them to overcome.
The lack of milkweed is not the only problem they face. Changes in pesticide use, illegal logging in the mountains of Central Mexico where they shelter for the winter, and changes in land use such as development in coastal California and Midwestern communities are threats to monarch habitat.
The Center of Biological Diversity, The Center for Food Safety, the Xerces Society and Professor Lincoln Brower petitioned the U.S. Fish and Wildlife Service to list the butterfly as a threatened species under the Endangered Species Act. Different groups hold various opinions on whether the best path forward is to list the butterfly. Everyone seems to agree that ways must be found to increase habitat. Those opposing the listing fear that some of the regulations that flow from the action may do more harm than good.
What Should We Do?
Regardless of the outcome we can all educate ourselves and help establish habitat for pollinators planting shrubs and flowers they favor and making sure we include local varieties of milkweed for the monarchs. The use of government lands – like highway medians for habitat – may help and decreased mowing costs could save taxpayers money.
One innovative project Dr. Oberhauser is involved in plants habitat for monarchs and other pollinators around solar farms. This is a great way for developers to easily and cost-effectively incorporate region-specific, deep-rooted grasses and wildflowers in the land management practices for solar farms.
The Monarch Butterfly Conservation Fund focuses on three priority conservation needs to restore the monarch butterfly to a more robust and healthy population: habitat restoration to plant native milkweed for caterpillars and nectar plants for adults in both large, contiguous areas as well as in smaller patches, especially in edge habitat along the butterfly's migration route, outreach and education in urban and rural communities, with a focus on youth engagement, and native seed production and distribution to increase production and availability of seeds and plants essential to habitat restoration, says the National Fish and Wildlife Foundation.
But what about consumers? Should they be turning their lawns into pollinator gardens? Oberhauser says yes. Monarch Watch offers a WayStation program that provides guidelines and seeds for home gardeners, schools, businesses, parks and other sites.
“In the end, it makes so much sense, because pollinator gardens provide water control in areas where run off is a problem. Garden plants and prairie plants that people would put in a butterfly garden have deep roots, so they are stabilizing the soil, preventing erosion, and soaking up water. There are many benefits to pulling out a little bit of grass and putting in a garden,” Oberhauser adds.
Dr. Blodgett agrees. She says that the Iowa Monarch Conservation Consortium is researching how many and what types of milkweed plants need to be planted on the landscape. They will also determine which milkweed species are best for monarchs in different parts of the state and how best to establish milkweeds with other flowering plants that provide needed nectar sources for the adult butterflies. Milkweed planting in gardens, highway right of ways, state parks and other public land will be important. Based on the current science, increasing the amount of milkweed in rural areas will be essential to the conservation of the monarch, she says.
“In Iowa and the Midwest, with a high proportion of land in agricultural production, having a farmer-led initiative that engages a broader public is so important to having an impact on monarch butterfly populations. But it is important to note that we feel there is land available on the rural landscape, outside of corn or soybean production fields that would be ideal for monarch habitat too. There are areas around barns, field edges, gardens, edges of waterways, and lands that have been set aside – not well suited for agricultural production but that would support monarch habitat. The monarch butterfly is a strong flier, moving readily between patches in a landscape that supports the approach we are taking, creating many milkweed patches for the butterfly to visit,” says Blodgett. “I think it will take a multi-pronged approach to improving monarch habit.”