U.S. scientists to study monarch butterfly numbers for protected status

Monarch butterflies in Thousand Oaks in 2012.
(Gary Friedman / Los Angeles Times)
Share via

For scientist Tierra Curry, the monarch butterfly is part of the American experience.

Native to North America, once present in every U.S. state except Alaska, the insects with the distinctive and colorful wings are known for their spectacular migration each year from Mexico to Canada and back.

But scientists like Curry have seen their numbers plummet: Monarch populations have dropped by 90% in the last two decades alone.

Now Curry, a senior scientist with the Center for Biological Diversity, sees some hope.

On Monday, the U.S. Fish and Wildlife Service announced that it would conduct a one-year status review of the butterfly species to determine whether it warranted Endangered Species Act protection.


“This will be a rallying point and hopefully a turning point for the population,” Curry said. “This announcement shows how big the problem is.”

The process will include a public comment period, during which the federal agency will gather new data on the health and numbers of monarchs in the United States. Eventually, officials will determine whether the insects will be proposed for protection, put on a waiting list or deemed not worthy.

“The Endangered Species Act is the most powerful tool available to save monarchs, so I’m really happy these amazing butterflies are a step closer to the protection they so desperately need,” Curry said.

Monarch populations have dropped from a recorded high of approximately 1 billion butterflies in the mid-1990s to 35 million last winter, the lowest number ever recorded, statistics show.

Scientists attribute much of the decline to herbicides used with genetically engineered crops in the Midwest, where most monarchs are born, activists say. Pesticide spraying has wiped out milkweed plants in corn and soybean fields.

Since the mid 1990s, scientists estimate that the once-common iconic orange and black butterflies may have lost more than 165 million acres of habitat — an area about the size of Texas — including nearly a third of their summer breeding grounds.


Scientists predict that the monarch’s entire winter range in Mexico and large parts of its summer range in the states could become unsuitable because of changing temperatures and increased risk of drought, heat waves and severe storms, the Center for Biological Diversity said in a news release.

Found throughout the United States during summer months, in winter most monarchs from east of the Rockies converge in the mountains of central Mexico, where they form tight clusters on just a few acres of trees. Most monarchs west of the Rockies migrate to trees along the California coast for the winter.

“We hope the announcement today is the beginning of a move to save these creatures,” Curry said. “These are the butterflies we used to chase through our backyards as kids. Nobody wants to see them gone.”

Twitter: @jglionna