population, which lives west of the Rocky Mountains, stood in the millions in the 1980s. In 2017, an annual count found 200,000 butterflies. In 2018, the tally fell to about 30,000 a figure that held steady last year, said Elizabeth Crone, a biology professor at Tufts University in Medford, Mass.
Date: Mar 20, 2020
Category: Science
Source: Google
Monarch butterflies disappearing from western North America
Elizabeth Crone, Tufts University professor and a co-author on the study, says that "The hard part of being a conservation biologist is documenting species declines. The exciting part is figuring out how to help declining species recover. In the 20th century, we brought bald eagles back from the bri