Monarch butterfly population in decline due to these three critical factors

While most butterfly species (and there are 300 species in Canada) overwinter as an egg, caterpillar, chrysalis or adult butterfly, the monarch’s epic migration is truly inspiring. These tiny insects travel 4,000 to 7,000 kilometres to escape the cold of winter.

There are two groups of monarchs in Canada: the population east of the Rocky Mountains, which migrate to Mexico, and the population west of the Rockies, which migrate to California.

But the monarch population is in decline.

“This year the monarch population is the lowest it has been since record keeping began in 1994,” says Jennifer Tremeer, the education and services coordinator at the Cambridge Butterfly Conservatory.

“The monarchs covered just 0.67 hectares of their overwintering grounds, compared to 1.19 hectares last year. It is estimated that monarchs gather in clusters of approximately 10 to 50 million monarchs per hectare in the overwintering grounds in Mexico. This translates to only about 33 million monarchs total this year in Mexico, compared to a peak of 1 billion in 1996. This drop confirms what scientists and monarch enthusiasts have long suspected: that there’s a long-term statistical trend of monarch decline.”

So what’s the cause of this decline?

“There are three main reasons for the decline,” says Tremeer. “The use of genetically modified, herbicide-resistant crops that destroy milkweed and nectaring habitat, the deforestation in Mexico, and the recent bouts of severe weather.”

The biggest threat throughout North America is habitat loss. Milkweed is the only plant that a monarch eats, and agricultural practices throughout North America are contributing to milkweed habitat loss. Modified crops allow farmers to spread pesticides on corn and soybeans, killing off other types of plants.

“Monarch habitat is also being lost to urban sprawl as more land is converted to houses, shopping malls, and roads,” says Tremeer.

And although the news sounds bad for the monarch, Tremeer remains optimistic.

“Unlike so many other environmental challenges, saving monarchs can be easy and fun and something everyone can get involved with,” she says. “It’s as simple as planting a butterfly garden that includes milkweed and nectar plants. Take your garden a step further and register it as an official weigh station with MonarchWatch and show that you are part of a growing network of people committed to preserving the monarch butterfly.”