In the past two decades, the monarch butterfly population east of the Rocky Mountains has declined by 87 percent. That’s due in part to the fact that the only plant that monarchs lay their eggs on – milkweed – has become scarcer thanks to farmers removing it from their fields. Scientists say that stopping the monarch’s decline will require planting some 1.8 billion stems of milkweed. And, according to new research, much of that milkweed can be planted in U.S. cities.
That’s the finding of a team at the Field Museum in Chicago, who published their findings in the journal Frontiers in Ecology and Evolution on Thursday. They say that cities could make up for almost one-third of all of the necessary milkweed plants. That’s 600 million stems.
“We don’t know how far off their estimates might be,” cautions Wayne Thogmartin, a research ecologist for the U.S. Geological Survey not involved with the study. But, he adds, this is “the best study of milkweed density in urban settings and perhaps any setting.”
