Monarch butterflies are in trouble. Populations of these impressive insects, which weigh less than a gram each and migrate thousands of miles each year from the Eastern United States to central Mexico (and back) are dwindling.
Ecologist Sonia Altizer wants all of us to understand why and to help this depopulation to stop. “The last three consecutive years have [shown] the lowest numbers of monarchs ever recorded in Mexico,” she says in a talk at TEDxUGA, referring to the 2011-2012, 2012-2013 and 2013-2014 surveys of wintering monarchs. In 2012, monarchs covered 2.89 hectares of forest in Mexico wintering sites; in 2013, 1.19 hectares; in 2014, 0.67 hectares. This year, though the number of hectares rose, most likely due to favorable breeding conditions, it is still “the second smallest area occupied by these butterflies in Mexican sanctuaries since 1993,” reports the World Wildlife Fund.
“There’s a lot of different challenges facing monarchs,” Altizer says, “ranging from climate change and drought to deforestation and illegal logging in Mexico, disease … even road strikes and car strikes along roads during the fall migration,” but one that stands out to the ecologist most is the decrease of milkweed plants in the U.S. Milkweed is the monarch’s main food source, Altizer says, and the weed has been historically found in Midwestern crop fields, but with the increase in agricultural use of pesticide thanks to pesticide-resistant crops, milkweed populations are dying out, and with them, monarch caterpillars, Altizer says.
Though these resilient creatures have astonishing abilities, from being able to navigate across a continent to finding, as Altizer points out, “the same patches of [wintering] forest when they themselves have never been there before,” less than one out of every ten monarch eggs will survive to become an adult butterfly, Altizer’s research group reports.
But all hope is not lost for the monarch, Altizer says. “There are small things that each of us can do that, collectively, can make a big difference.” These range from participating in monarch citizen science projects to help identify and count monarchs to planting butterfly gardens that provide monarchs with food sources.
To learn more, watch Altizer’s talk below: