Since 2014, conservationists have been trying to secure protections for the monarch butterfly under the Endangered Species Act. The butterfly—whose signature black-and-white speckled orange wings are impossible to miss—has seen its numbers drop by 80 percent in North America over the last 20 years.
New research, however, paints a promising future for the species in a surprising place: our cities.
A pair of studies from the Field Museum in Chicago published Friday look at the role urban centers can play in saving the monarch butterfly, as well as other pollinators, from extinction. What these insects need is milkweed, the only plant the butterflies can lay their eggs on. Unfortunately, habitat loss has made it difficult for these bugs to find enough milkweed to breed. But more than 100 species of milkweed exist, so the team of researchers got to work figuring out how much already exists in U.S. cities, and how much room cities have for even more milkweed.
Until this study, these questions have largely gone unanswered. The assumption was that cities wouldn’t offer very much in the way of new monarch habitat. But that couldn’t be further from the truth.
As it turns out, cities east of the Rocky Mountains—the habitat for the eastern monarch butterfly and the focus of this research—could support up to 30 percent of the 1.8 billion stems of milkweed the population needs to reach sustainable levels. The researchers came to this conclusion after looking at high-resolution images of land cover, as well as conducting field research, in four cities the butterflies fly through: Chicago, Kansas City, Austin, and Minneapolis-St. Paul. The team, however, only used its data from Chicago (because it was the most comprehensive) to extrapolate the estimate for all urban areas, a key limitation of this study.
Regardless, all this data allowed the scientists to estimate how much “plantable space” exists in these cities, including areas where pollinator habitats already exist and where they could theoretically exist. The team collected data from 2016 and 2017 to estimate the density of milkweed already present in each city. The authors looked at natural areas—like state parks and wilderness areas—where they expected to find higher concentrations of milkweed, as well as more randomly-chosen areas. The researchers were surprised to find millions of milkweed stems throughout these cities (more than 15 million in the case of Chicago).
In all these cities, about half of all the plantable space was in agricultural areas, but residential single-family areas came in second. That means individuals have a chance to show up for the monarch butterfly—if they’re willing to leave behind their pristine green lawns for a little bit of native milkweed. (Lawns suck, anyway.)
“We’re really hoping to shift public perception of what people think of as beautiful or appropriate,” said author Abigail Derby Lewis, a senior conservation ecologist at the Field Museum, to Earther. “So much of the yards, they’re just grassy lawns, and they could be so much more.”
That was another key piece of the research: finding out how people felt about monarch butterflies. The team asked 734 individuals both open-ended, fill-in-the-blank questions and yes-or-no questions to learn how many were already planting milkweed and what it’d take them to grow if they weren’t already. Only 226 indicated they were growing plants, and 81 percent of those were growing milkweed. This data was not, however, representative of the general population but, rather, representative of the interested public.
“We think that if we can get our first wave of people who are starting to plant milkweed, that it can really turn into a snowball effect where other folks are willing to do the same because they start to learn about what their neighbors are doing, and it catches on,” said author Mark Johnston, a conservation ecologist with the Field Museum, to Earther.
Planting milkweed wouldn’t only help save the monarch butterflies. It’ll help save the honeybees, too! These are pollinators we need for our food systems to flourish and ones that are currently on the decline.
Cities aren’t the only answer, of course, but they’re a key piece of the puzzle. And they can play a damn big part.
“This shows that you can actually put really functional habitat on the ground,” Derby Lewis told Earther. “It’s not just nature out in Yellowstone. It’s not just nature somewhere out there. What we do in our cities, in our backyards, front yards, churches, parkways, vacant lots, cultural institutions, golf courses—all of these things!—really have this enormous collective impact.”