Each spring, the California sky becomes a sea of orange and black. Thousands of monarch butterflies take flight in one of the world’s most famous migrations. The butterflies have spent the winter clustered in trees along the coast of California. Now, they’re migrating north, flying up to 100 miles a day.
However, fewer monarchs than ever are making that journey this year. In December, scientists announced that the number of monarchs in California was the lowest on record. It’s part of a trend that’s seen the monarch population plummet over the past 20 years.
“The population was already not doing well, and then it took a nosedive,” says Emma Pelton. She is a scientist at the Xerces Society, a conservation group that tracks western monarchs. Pelton and other experts are worried that western monarchs may soon completely disappear.