Volunteers plant hundreds of milkweed plants in hopes of supporting the dwindling Western monarch population in California.

ARVADA, Colo. — The National Wildlife Federation (NWF) said monarch butterfly populations have declined upwards of 90% in recent decades. "There’s been an impact of climate change, habitat loss [and] ...

The number of monarch butterflies spending the winter in the western United States has dropped to its second-lowest mark in nearly three decades as pesticides, diminishing habitat and climate change ...

The monarch butterfly is facing an uncertain future: Populations have been slowly declining for years, shrinking by as much as 90% due to human development. Last winter’s count of overwintering ...

The Western population of the monarch butterfly has declined to a near-record low with fewer than 10,000 found living in California this winter, a foreboding sign for the future of the beloved ...