SAN FRANCISCO — The western monarch butterfly population wintering along California’s coast remains critically low for the second year in a row, a count by an environmental group released Thursday showed.

The count of the orange-and-black insects by the Xerces Society, a nonprofit environmental organization that focuses on the conservation of invertebrates, recorded about 29,000 butterflies in its annual survey. That’s not much different than last year’s tally, when an all-time low 27,000 monarchs were counted.
“We had hoped that the western monarch population would have rebounded at least modestly, but unfortunately it has not,” said Emma Pelton, a monarch conservation expert with the Xerces Society.
By comparison, about 4.5 million monarch butterflies wintered in forested groves along the California coast in the 1980s. Scientists say the butterflies are at critically low levels in the Western United States due to the destruction of their milkweed habitat along their migratory route as housing expands into their territory and use of pesticides and herbicides increases.
Researchers also have noted the effect of climate change. Along with farming, climate change is one of the main drivers of the monarch’s threatened extinction, disrupting an annual 3,000-mile (4828-kilometer) migration synched to springtime and the blossoming of wildflowers.
Western monarch butterflies head south to California each winter, returning to the same sites and even the same trees where they cluster to keep warm. The monarchs generally arrive in California at the beginning of November and spread across the country once warmer weather arrives in March.

The Decision on Whether the Butterfly Will Be Listed as Threatened Is Expected by December

On the eastern side of the Rocky Mountains, another monarch butterfly population travels from southern Canada and the northeastern United States across thousands of miles to spend the winter in central Mexico. Mexican officials said last year the butterfly population wintering there was rebounding but they have not yet released this year’s count.

A 2017 study by Washington State University researchers found the species likely will go extinct in the next few decades if nothing is done to save it.
The monarch is now under government consideration for listing under the U.S. Endangered Species Act. The decision on whether the butterfly will be listed as threatened is expected by December.
While helping the western butterflies could seem daunting, Pelton said the fact that the population didn’t shrink any further is encouraging.
Pelton said people can help by planting early-blooming flowers and milkweed to fuel migrating monarchs on their paths to other states.
The Xerces Society is working with the state of California to protect the butterflies’ wintering sites and develop new sites in state parks.
“There are still thousands of monarchs (wintering) along the coast, so we can take heart that it’s not too late to act,” Pelton said.