Monarch butterflies are disappearing at an alarming rate, with a survey last week showing that the population has plummeted to the lowest level seen in the 20 years that data has been collected.
At their peak in 1996, the big, beautiful butterflies, with their regal orange-and-black stained-glass wings and a fondness for milkweed and other nectar-rich wildflowers, occupied nearly 45 acres of forest in their winter home in Mexico's mountains.
The Mexican government and the World Wildlife Fund said at a news conference last week that the span of forest inhabited by the overwintering monarchs shrank last month to only 1.7 acres — the equivalent of about 11/4 football fields. Not only was that a record low, but it was just 56 percent of last year's total, which was itself a record low.
The acreage covered by monarchs, which has been surveyed annually since 1993, is a rough proxy for the actual number of butterflies that survive the arduous migration to and from the mountains.
The declining monarch population will be the subject of a lecture next week in Lexington by Chip Taylor, a University of Kansas professor who specializes in insect ecology and is the founder and director of the advocacy organization Monarch Watch. "Monarch Conservation: Challenges and Opportunities," on Feb. 12, is part of the Friends of The Arboretum lecture series.
Each year, the monarchs migrate between summer grounds in the central and eastern United States and Canada to warmer sanctuaries in Mexico. Their flutter-and-glide rides can exceed 3,000 miles in each direction. The monarchs converge to hang out and overwinter in a remote area in Sierra Madre fir forests. There, they rest in high-altitude habitats that since 1986 have been protected by the Mexican government as the Monarch Butterfly Biosphere Reserve and since 2008 have been a UNESCO World Heritage site. On the western side of the Rocky Mountains, monarchs follow a shorter course, to groves along California's Pacific coast.
The monarchs' population decline is probably due to a combination of unfavorable weather patterns, Taylor said, and a major habitat loss during the past couple decades.
Monarchs cycle through a metamorphosis from egg to caterpillar, then chrysalis and finally butterfly, going through multiple generations during their travels. Eggs and caterpillars depend on milkweed as a specific host; butterflies can sip nectar from a variety of flowers.
At one time, fallow fields, wayside hedges and woodlots provided plentiful habitat, but human population increases call for more housing, which leads to commercial and industrial construction. Open land where these plants once thrived is being developed.
There is a movement to encourage gardeners to plant monarch-attracting locally sourced milkweed and native flowers, including goldenrod and liatris in home gardens, parks, schools and landscaped business grounds. Taylor's group calls these gardens "way stations" and keeps a registry of them, searchable by location, at Monarchwatch.org.
Timing is important. University of Kentucky entomology professor Ken Yeargan, who conducts monarch research, said monarchs have been spotted arriving in Kentucky in late April and usually are laying eggs from mid-July through September. That would be a good time to have milkweed in place.
"It has been apparent that the eastern North American population was in trouble for more than a year," he said of monarchs. "I have taught introductory entomology for almost 40 years at UK, and last semester was the first time that I ever asked my students to not collect monarch butterflies for their insect collection project."
Last year, the Lexington chapter of Wild Ones, an organization that encourages the use of native plants and ecologically sound principles, helped establish about 30 monarch way stations in Central Kentucky.
Despite the rarity of monarch sightings in the area last year, many caterpillars were spotted on milkweeds planted at a way station at Floracliff Nature Sanctuary in southern Fayette County.
The New York Times News Service contributed to this report. Susan Smith-Durisek is a master gardener and writer from Lexington. Email: firstname.lastname@example.org. Blog: Gardening.bloginky.com.