Ann Heisenfelt/Associated Press
In this July 22, 2012 file photo, a monarch butterfly eats nectar from a milkweed plant.
Ann Heisenfelt/Associated Press
Researchers at the Field Museum say Chicagoans could play a big role in helping boost the declining population of monarch butterflies.
Two new studies led by conservation ecologists at the Field found that urban areas east of the Rocky Mountains have the potential to plant more than 500 million stems of milkweed. Milkweed is essential to monarchs — the familiar orange and black butterflies — as it's a food source and the only plant where they lay their eggs.
Milkweed continues to disappear due to herbicide use, and as grass and other plants have been favored over native plants. The decline of milkweed has led to the loss of more than 80% of the monarch population across the Midwest and Eastern United States during the last 20 years.
To find whether cities could play a part in boosting the monarch population, the studies measured how much milkweed is currently available in urban areas east of the Rockies and how much more could potentially be planted.
"Each of us individually who have any kind of ownership — it may be a yard, it may be a community garden, it may be a pot on your balcony — that action [growing milkweed] really makes a difference," said Abigail Derby Lewis, a senior conservation ecologist at the Field and one of the lead researchers.
The researchers found that more than 15 million milkweed stems already exist throughout Chicago, but the city has the potential to nearly double that number by making use of available spaces, including residential areas such as home gardens and lawns, apartments and condos.
They also found that if just 2% of green space in urban areas east of the Rockies grew milkweed, that could build up to a third of the habitat needed in North America to help sustain the monarch population.
But Derby Lewis said in order to get people to plant milkweed, some preconceptions about the plant need to be dispelled — namely that it might be a weed, as the name suggests.
Milkweed is a native flowering plant that comes in a range of colors and sizes. In addition to being good for monarchs, Derby Lewis said the plant's deep roots also benefit humans by capturing more water than grass and reducing maintenance costs.
The plant also attracts other pollinators that might not be as popular as butterflies, such as beetles and bees. But those insects are essential to a lot of foods that humans consume, said Mark Johnston, a conservation ecologist at the museum and one of the lead researchers.
"Those pollinators are also involved in the agricultural industry of providing us with fruit trees. So if you like apples, if you like almonds and avocados, then you also like pollinators and you should support them," he said.
In conjunction with the studies, the Field launched a community science project that trains people on how to support monarchs at home, and asks participants to help gather data by monitoring the monarchs weekly.
The studies were initiated four years ago when the U.S. Fish and Wildlife Service asked the Field to study whether more could be done in urban areas to reverse plunging monarch numbers before the butterflies might be considered an endangered species. While the studies found that planting milkweed could make a difference, it remains to be seen whether struggling monarchs will be added to the endangered species list.
Marley Arechiga is a news intern for WBEZ. Follow her@marleyarechiga.