Disappearance of Iconic Monarch Butterfly Linked to Milkweed Decline

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Tom Weissling, a professor in the University of Nebraska-Lincoln’s Department of Entomology, spends his summer combing through fields searching for milkweed and monarch larvae. (Mike Tobias for Harvest Public Media)

The population of monarch butterflies has declined so dramatically in recent years that the iconic insect is being considered for the U.S. Fish and Wildlife Service’s endangered species list. In Nebraska and across the other areas of the Midwest, a stop on the monarch migration route, efforts are underway to determine the scope of the decline.

Carrying notebook and camera, Tom Weissling wades through waist-high grass and plants at Nine Mile Prairie west of Lincoln, Neb. The associate professor in the University of Nebraska-Lincoln’s Department of Entomology periodically stops, looks closely at plants and takes notes and pictures. It’s how he spent a lot of his summer, combing the state for signs of something that’s getting harder to find: monarch butterflies.

“Mostly I’m trying to find Monarch larvae. Weissling said, walking through a field. “In my last trip I looked at several hundred plants and I only found about four larvae.”

(CLICK HERE to watch a video story on Weissling’s survey)

Weissling is also looking for milkweed. The connection is important because monarchs lay their eggs exclusively on milkweed, and it’s the only thing the larvae will eat. Weissling’s rough survey took him to about two-thirds of Nebraska’s counties, and is something of a starting point in determining the decline of monarchs in the state.

An Iowa State University report estimated an 81 percent decline in the monarch population in the Midwest between 1999 and 2010, with a 58 percent decline in milkweed presence during the same time.

“Less milkweed will equal fewer monarchs overall,” Weissling said. “I don’t think that’s something we want to experience.”

The reasons behind the decline in monarchs can be controversial. Some say milkweed loss is caused by increased use of agricultural herbicides. Others point to a loss of forestland in Mexico where monarchs winter, and temperature fluctuations.

North American monarchs are the only butterflies that make a massive migration to California and Mexico each winter—up to 3,000 miles. They are now being considered for the U.S. Endangered Species List.

National Geographic

North American monarchs are the only butterflies that make a massive migration to California and Mexico each winter—up to 3,000 miles. They are now being considered for the U.S. Endangered Species List.

What’s happened over the last 20 years is we’ve seen big changes in the landscape,” said Duane Hovorka, executive director of the Nebraska Wildlife Federation. “Loss of native prairies. Big changes in ag production technologies.”

Regardless of the cause, Hovorka said these are big changes that require a big response. Nebraska may develop a statewide conservation plan, Hovorka says, and strategies for increasing milkweed.

“We think we can do that by planting seeds and live plants on public lands, parks and wildlife management areas, on some of the conservation lands that are owned by places like the Audubon Society and the Crane Trust and the Nature Conservancy,” Hovorka said. “We’d also like to see some different management along county and state roads. Right now we do a lot of mowing in places and at times we don’t need to, and so that takes out the milkweed populations.”

Weissling said they could also work on convincing businesses and homeowners to embrace milkweed as an addition to their landscaping, and just think differently about where milkweed could be allowed to grow.

“My approach would be you don’t have to get rid of all of it,” Weissling said. “Maybe think of areas that are marginal for crops or areas that you don’t put in any crop production that maybe you could grow some milkweeds on.”

It could take a lot of milkweed to reverse the trend. Hovorka said the U.S. Fish and Wildlife Service is talking about a five-year goal of having a milkweed presence on 7 million acres nationally, primarily in the Great Plains. He said a million of those acres could be in Nebraska.

“We’re not talking about fields of milkweed,” Hovorka said. “There are some milkweed seed plots that are being planted that we need because we need a lot of seed in order to put that many plants out. But for the most part this is scattering milkweed across the landscape in school yards and in backyards. On ranches, on public lands.”

Nebraska Game and Parks has already started doing some of this work.

“We’ve got plans to do more but we’ve started planning milkweed production plots on more than two dozen of our wildlife management areas, and that will serve as a seed source to do more habitat work in the future,” said Scott Taylor, Nebraska Game and Parks Commission Wildlife Division administrator. “We’ve also started planning milkweeds across the state.”

That includes working with partner organizations in September to plant 3000 milkweed seedlings along stretches of the Cowboy Trail, a Game and Parks recreational trail that runs from Norfolk to Valentine. The project was funded by a $150,000 grant from the National Fish and Wildlife Foundation.

“Federally and regionally and within the state, there’s just a groundswell of interest right now in making sure monarchs are doing better than they appear to be doing the past few years,” Taylor added.

Bringing back monarch habitat, Hovorka says, is particularly important because it has a broader impact than the loss of butterflies.

“We have bees and other pollinators that are critically important to the ag economy and to growing some of the foods that we have,” Hovorka said. “So it’s not just about losing monarch habitat. We’re losing bees. We’re losing the other pollinators. The monarch is sort of the big, flashy, bright species that people love. It’s an easy thing to talk about. But what we really need to do around the landscape, while we’re restoring habitat for monarchs, we’re also restoring habitat for bees, for other pollinators, we’re diversifying the prairies that we have, and so that’s good for a lot of different kinds of wildlife.”

Back at Nine Mile Prairie this summer, Weissling flipped over a milkweed leaf to expose a yellow and black striped monarch caterpillar. He found 14 of these during his statewide summer survey, but said the statistics are more starting point than barometer at this stage. Just another part of an effort Weissling hopes will save what he calls the bald eagle of American insects.

Video Dispatch

Travel with Tom Weissling as he combs through fields searching for milkweed and monarch larvae.


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