The population of eastern monarch butterflies has been dropping steadily for decades, with some estimates suggesting their numbers are just 20 percent of what they once were. According to a new study, climate change is the biggest driver.
Pesticides, climate change, and habitat destruction have put North American monarchs in a freefall. A proposed bill might help save them—but only if Congress acts quickly.
The iconic monarch butterfly travels thousands of miles south to overwinter in Mexico. But factors including the changing climate are challenging its existence — new figures show it's declined 15 percent from last year.
