Monarch butterfly fans work to restore plantings

The common milkweed is no longer common, and neither is the beloved monarch butterfly, which depends upon milkweed for its existence.

Monarch larvae hatch and feed exclusively on milkweed, an Iowa native that has fallen victim to changing farming practices.

'The monarchs are a beautiful and beneficial part of nature that we cannot afford to lose,” said Patty Ankrum of Mount Vernon, a leader of the 115-member monarch activist group, Monarchs in Eastern Iowa.

'I noticed the monarch decline on a personal level, and we are trying to do something about it on a personal level,” said Ankrum, who like many other members of the group is planting milkweed in her garden and raising caterpillars in her house.

While such grass roots efforts cannot begin to replace all the milkweed lost to increasingly effective herbicides, 'we can't passively wait for the monarchs to disappear,” she said.

In addition to the observations of Ankrum and other nature lovers, the monarch's decline has been quantified by scientists who since 1993 have been measuring the area covered by monarchs clumped together in their Mexican wintering roosts.

During the past winter, monarch coverage fell to an all-time low of 1.65 acres, down from 44.5 acres during their peak in 1995.

Scientists studying the monarchs' decline attribute it to several factors including habitat destruction at their wintering site and unfavorable weather along the monarchs' migration route and at their breeding and wintering sites.

But the main factor, most agree, is the loss of milkweed and especially the common milkweed, whose pods filled with downy seeds were indeed common upon Midwest landscapes until the 21st century.

The decline of monarchs corresponds closely with the decline of milkweed, according to John Pleasants, an Iowa State University biologist who has been studying their relationship for 15 years.

Pleasants said he began studying monarchs to test a theory that pollen from corn genetically modified to kill the European corn borer - commonly called Bt-corn - was having an adverse effect on monarchs.

Though that theory was disproved, Pleasants said he observed a plummeting of milkweed populations as the use of the herbicide glyphosate proliferated with the widespread planting of Roundup-ready crops.

'Glyphosate is so much more potent for milkweed than the herbicides previously used,” he said.

Between 1999 and 2009, in crop field plots monitored by Pleasants and a colleague, once plentiful milkweed all but disappeared, he said.

'We estimated that milkweed in the Midwest declined 64 percent since 1999, which is fairly comparable to the decline of monarchs wintering in Mexico,” he said.

Pleasants estimates that the loss of milkweed in monarchs' breeding habitat constitutes about 80 percent of the cause of their decline.

Other scientists rate adverse weather and climate as an equally important cause of the distinctive orange-and-black butterfly's decline.

Buchanan County naturalist Sondra Cabell, who has been tagging and monitoring monarchs since 1987, said she's seen a lot of ups and downs, but their decline became most noticeable to her in the 2012 drought.

'The caterpillars did not survive the heat, and the milkweed did not survive the drought,” she said.

Cabell recorded her lowest tagging number and her lowest number of summer observations of caterpillars and butterflies in 2012, she said.

'It's not just one factor. Habitat is huge, but weather and climate influence monarch populations,” she said.

'We need the weather to stop being so extreme. A few good years of stable weather and we would see better numbers,” said Stephanie Shepherd, manager of the Department of Natural Resources' wildlife diversity program.

Butterfly expert Dennis Schlicht of Center Point, co-author of the 2007 book, 'The Butterflies of Iowa,” said he thinks there is an X Factor involved in the monarchs' decline.

'There is this overlying blanket thing going on, causing a general downturn in the diversity of butterfly species and their overall numbers,” said Schlicht, who has conducted butterfly field surveys for decades.

Prairie butterflies with no affinity for milkweed also are disappearing from preserves and pastures, he said.

'Is it something to do with climate change? Is it related to increased aerial crop sprayings for insects and fungus? We don't know,” he said.

Debbie Jackson, a conservation specialist with Monarch Watch, a leading monarch conservation group, said it would be a shame to lose the monarch migration, one of nature's most complex and intricate spectacles.

'It takes successive generations to accomplish. No single butterfly ever starts and finishes a migration,” she said.

The complete migration takes at least six months, about three times the life span of a typical breeding monarch, so the generation that travels south in the fall enters a phase called diapause, in which reproduction, with its accompanying stress, is suspended, allowing them to live longer, she said.

On their way back in late winter, they reproduce and die, leaving the remainder of the northward journey to their offspring.

Jackson, who grew up in Marion and now lives in Michigan, said monarchs, lazy flutterers in their summer range, typically travel 30 to 50 miles per day during migrations with a flap-flap-flap-glide cadence.

'No one shows them how to do it. Their ancestors are all dead. They are able to read magnetic fields from the north and south poles for guidance,” she said.

Monarch conservation efforts focus on re-establishing milkweed throughout their range.

For the past decade, Linn County has been including butterfly milkweed and swamp milkweed in the seed mix used for native plantings along county roads, said roadside vegetation manager Rob Roman.

'Really because of the monarch issue we are going to start planting common milkweed, which the monarchs prefer, next year,” Roman said.

ISU's Pleasants said expanding roadside milkweed plantings and including milkweed seed in the mix used to establish Conservation Reserve Program vegetation would go a long way toward helping monarchs recover.

The additional milkweed density, he said, would more than compensate for the shrinkage of CRP grasslands from a 36.8 million acre peak in 2007 to a cap of 24 million acres in 2018 under the current farm bill.

Schlicht, however, questioned the benefit of roadside milkweed plantings, asserting that vehicle collisions are a leading cause of monarch mortality.

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