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The number of monarch butterflies has decreased by 80 percent over the past 20 years, with numbers so low now that scientists say the migrating species is not sustainable unless milkweed habitat increases dramatically, boosting their numbers.

But there is hope, with many people working on conservation strategies.

In Iowa, a group called the Iowa Monarch Conservation Consortium, made up of 40 organizations, including the Iowa Department of Agriculture and Land Stewardship, the Iowa Department of Natural Resources and Iowa State University, has set a goal of establishing 480,000 to 830,000 acres of new monarch habitat in Iowa in 20 years, or by 2038.

That means establishing 127 million to 188 million new stems of milkweed in Iowa and a total of 1.3 billion in the North Central states that comprise the butterflies' breeding ground.

Is that even possible?

Asked that question, Steve Bradbury, an entomology professor at Iowa State pauses a second and then says, "It will be challenging, that's for sure."

Success will require an "all hands on deck" approach, involving farms, schools, churches, parks, backyard gardens, roadsides  — any little nook and cranny that can be planted in milkweed, he said.

"But there is room," he said. "There is land not devoted to crops that could be habitat."

The acreage and milkweed stem goals are what scientists have concluded are minimally necessary to boost the adult population of monarch butterflies to about 225 million by 2020, a sustainable number, Bradbury said.

"Based on current, best available scientific information from the United States, Canada and Mexico, increasing the fall eastern monarch population to 225 million butterflies by 2020 should be sufficient to maintain the continental migration, even in the face of extreme climate events," according to the consortium's strategy report issued in March.

At present, the butterfly population is about half that.

During the monarchs' winter migration to Mexico, the butterflies occupied 2.48 hectares, representing about 100 million adults, Bradbury said. The all-time low was during the winter of 2013-14, when butterflies occupied only 0.67 hectares, he said.

The goal is 6.5 hectares (roughly 16 acres), Bradbury said.

Little tracts are good

In establishing milkweed habitat, "monarchs don't need big tracts," he said. "If fact, they will do better with lots of little habitats scattered across the landscape. They will lay more eggs with a lot of little habitat patches, say a half-acre to five acres. They don't lay all their eggs in one basket. They spread them across the landscape."

In other words, it would be better to have 100 one-acre patches scattered about than one, 100-acre tract.

This is good news for backyard gardeners who want to do something to help. And while there are numerous kinds of milkweeds, the ones that monarchs seem to favor are the swamp, common and butterfly weed, in that order, Bradbury said.

Female monarchs lay eggs exclusively on milkweed plants, so efforts focus on establishment of new milkweed stems. However, habitat plantings are expected to include a diverse array of nectar species to provide forage for adult monarchs throughout their life cycle and seasonal migrations.

The importance of Iowa and Illinois in the success of this effort cannot be overstressed.

Both states fall entirely within the monarch's northern breeding core. "This means that every patch of milkweed habitat added in Iowa counts," Chuck Gipp, former director of the Iowa DNR said earlier this year. "The recovery cannot succeed without Iowa," he said.

And, by extension, it cannot succeed without Illinois, either.

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