Visiting a family cottage near Port Elgin, Ont., in the 1990s, Theresa Forte remembers “so many monarch butterflies, it almost looked like a cloud of them.”
We’ve known those orange-and-black flurries are in crisis—across North America, numbers have fallen more than 80 per cent in 20 years—and recent research confirms the much-loved monarch is now facing ill winds and a changing landscape.
Last November, surveyors counted fewer than 200,000 butterflies in coastal California’s wintering grounds, the source for B.C.’s monarchs—a drop of more than a million since 1997.
The story is similar in Mexico’s Oyamel fir forests, where the rest of Canada’s monarchs winter. Butterflies roost so densely there that officials measure hectares, not individuals. This winter, the insects huddled in 2.48 hectares, a 15 per cent drop from the year before and down from 18.2 hectares in 1996–97.
Monarchs may be the ultramarathoners of the insect world, but development is making their 4,000 km route much harder to finish and survival much tougher when they arrive, says Tyler Flockhart, a migratory species researcher at the University of Maryland Center for Environmental Science.
Culprits include collisions with cars, pesticides, logging, and even guacamole. In February, Mexican authorities found an illegal 1.4-hectare avocado plantation carved into the monarch’s winter reserve—the latest sign that the boom in avocado consumption is encouraging growers to replace native forest with fruit trees. Still, don’t swear off avocado toast just yet, says Flockhart, at least until we know the extent of avocado’s impact.
The science is stronger on the herbicide-resistant crops that help farmers evict nectar-producing wildflowers and milkweeds from corn and soybean fields. “Milkweed is the only plant monarch caterpillars feed on,” he says. “We may have lost more than a billion milkweed plants in eastern North America alone.”
Finally, there’s wonky weather, including the hurricanes that hammered the migration route in 2017 and the balmy autumn that encouraged monarchs to linger in Canada. “When you see them at the end of October, you’re almost sure they won’t make it,” says André-Philippe Drapeau Picard, the project coordinator of Mission Monarch, which tracks milkweed and monarchs.
It’s a complex problem spread across three countries, but cottagers can help by planting native milkweeds and nectar-rich flowers, expanding natural areas around the cottage, and laying off pesticides. And if you see monarch adults and caterpillars, log them at mission-monarch.org to help the program to identify reproduction hot spots and eventually protect them.