A monarch alights on milkweed, a plant essential for the life cycle of the butterfly. (photo/Cindy Hadish)

While California is marking a record low number of overwintering monarch butterflies, counts in Mexico are more encouraging.

The latest survey in Mexico — where monarchs from Iowa overwinter — showed a doubling in population compared to last year.

Experts say further efforts are needed to bring monarchs back from their perilous decline, particularly by establishing more habitat with milkweed, the sole plant consumed by monarch caterpillars.

Related: Iowa central to proposed monarch highway

A monarch caterpillar munches on milkweed, its sole food source. (photo/Cindy Hadish)

Iowa officials called the recent survey in Mexico encouraging and cited Iowa’s critical role in providing summer breeding habitat for the butterflies.

See the difference between monarch and swallowtail caterpillars and read more  from the Iowa Department of Natural Resources about the recent numbers:

AMES, Iowa — This week, the World Wildlife Fund released its 2018-2019 overwintering monarch population report. Adult monarch butterflies covered approximately 15 acres of forest canopy in Mexico, a doubling of last year’s population, and a level not seen since 10 years ago.

The report provides hope, say leaders of the Iowa Monarch Conservation Consortium.

“Although the number of monarch butterflies overwintering in Mexico has rebounded considerably, turning this encouraging one-year population response into a consistent long-term trend depends on advancing conservation efforts that are critical to help monarchs survive and reproduce in Iowa and the Upper Midwest,” said Steve Bradbury, professor of natural resource ecology and management at Iowa State University.

Monarch butterflies face many challenges including the loss of milkweed and nectar plant habitat in its spring and summer breeding ranges. Female monarchs lay eggs exclusively on milkweed plants. National and state efforts focus on establishment of new milkweed habitat to reach conservation goals.

“This year’s high watermark is very encouraging, and Iowa has a critical role to play in providing summer breeding habitat for the monarch for years to come,” said Bruce Trautman, acting director of the Iowa Department of Natural Resources. “We have a really strong group with broad expertise working together to support the monarch recovery in Iowa and beyond.”

Habitat plantings include milkweed and a diverse array of blooming species to provide nectar for adult monarchs throughout their life cycle and seasonal migrations. The current Iowa Monarch Conservation Strategy seeks to establish approximately 480,000 to 830,000 acres of monarch habitat by 2038. Iowa’s strategy, combined with those of neighboring states, is designed to consistently maintain a yearly population of 225 million adult monarchs, or about 15 acres of occupied forest canopy.

“The monarch butterfly population numbers are encouraging and serve as a reminder of the importance and impact of our ongoing conservation efforts,” said Mike Naig, Iowa Secretary of Agriculture. “Iowa’s long-term strategy includes expanding habitat for monarchs on our agricultural land, urban areas, roadsides and other public land.”

The Iowa consortium is a group of 50 organizations, including agricultural and conservation associations, agribusiness and utility companies, universities and county, state and federal agencies. Roughly 40 percent of all monarch butterflies that overwinter in Mexico are estimated to come from Iowa and neighboring Midwestern states. Expanding monarch habitat in Iowa will play a major role in the recovery of the species.

“Progress always starts with good science, and our researchers continue to make strides to understand what it takes to improve and increase monarch habitat through a deeper understanding of biology and the environment,” said Daniel Robison, Endowed Dean of the College of Agriculture and Life Sciences at Iowa State University. “Our extension and outreach efforts, in coordination with regional, national and private partners, are doing much to provide the science-based information and education that ensures approaches to monarch conservation are as effective as they can possibly be.”

The Iowa strategy — developed by consortium members — guides the implementation and documentation of voluntary, statewide conservation efforts based on the best available science. Their approach fosters habitat improvements in rural landscapes that do not conflict with agricultural production, are sufficient in scale to support improved monarch breeding success and strive to complement other conservation programs.

To learn more about the Iowa Monarch Conservation Consortium, visit www.iowamonarchs.info