SAN FRANCISCO (AP) — The number of western monarch butterflies overwintering in California dropped by 30% last year, likely due to how wet it was, researchers said Tuesday.
Volunteers who visited sites in California and Arizona around Thanksgiving tallied more than 230,000 butterflies, compared to 330,000 in 2022, according to the Xerces Society, an environmental nonprofit that focuses on the conservation of invertebrates.
Scientists say the butterflies are at critically low levels in western states because of destruction to their milkweed habitat along their migratory route due to housing construction and the increased use of pesticides and herbicides.
On the eastern side of the Rocky Mountains, another monarch population travels from southern Canada and the northeastern United States to central Mexico.
Scientists estimate that the monarch population in the eastern U.S. has fallen by about 80% since the mid-1990s, but the drop-off in the western U.S. has been even steeper.
Persons:
Emma Pelton
Organizations:
FRANCISCO, Volunteers, Xerces Society
Locations:
California, Arizona, Pacific Northwest, Rocky, Canada, United States, Mexico, U.S