CHICAGO – First, the bleak butterfly news: The population of monarchs passing the winter in Mexico appears to have fallen. Now, the good news for Illinois’ state insect: The Field Museum in Chicago is trying to figure out what makes a successful urban monarch garden, and it’s not too early to start preparing for this summer.
The area covered by monarchs in Mexico has decreased by more than a quarter compared with last season, according to Mexico’s National Commission of Protected Natural Areas and World Wildlife Fund. Because the butterflies mass together on fir trees at their southern roosting grounds, populations are measured in hectares, or acres. This winter’s count is only about 5 acres, down from nearly 7 last year.
“When you have those really low numbers, you run the risk of a real catastrophic decline, like we’ve seen with the monarchs in California,” said Erika Hasle, a conservation ecologist at the Field Museum, where a community science project is now heading into its third season. “We’re not at that point yet with the monarchs east of the Rockies, but it’s a real risk and it’s a real concern. And it’s an indication that there’s something they’re not getting.”
The monarchs we see in Chicago are part of the eastern population, which accounts for nearly all the monarchs in North America, and includes a supergeneration that flies thousands of miles to Mexico. The western population, which winters in California, was found to number fewer than 2,000 monarchs in a Thanksgiving count – a record low, down from nearly 30,000 the prior year and more than a million years ago.