The Monarch, a species now in peril

Category: Science Written by Beth Owens 145 2

The Monarch butterfly  is an iconic species of North America, remarkable for its annual migration of 4,000 kilometers.


A study from 2016 suggests the Monarch could actually become “quasi-extinct” in the not-too-distant future.

contributor to the study was Iowa State University researcher John Pleasants, who has put a number on the odds of Monarch numbers falling so low that their migratory patterns will totally collapse; he believes there is a 11 to 57 percent chance that will occur.


While there are various contributing factors to their decline, the salient reason is the decline of milkweed crops. The flowery herbaceous perennial known for its milky juice is a mainstay for the monarch butterfly. Milkweed serves a number of medicinal purposes, but crops of the plant have been declining leaving the butterfly with diminished breeding grounds.

What is going on with the monarch?

Its population has fallen by more than 90% in 20 years. There were about 1 billion and there are only 60 million, according to Maxim Larrivée, head of research and collections at the Montréal Insectarium. “For 20 years, it has been decreasing, but since 2012, the population has crossed a new threshold,” he said. It has lost resilience. Any impact can have very important influences. ”

Where does the monarch live?

This 5 grams butterfly has a hectic life. In March, adults from the previous year left Mexico, where they spent the winter in highly concentrated colonies. They breed in Texas. Then the next generation rises to the northern United States, where a second breeding takes place. The first adults arrive in southern Canada at the end of May or in early June, and breed. This third generation lives all his life with us and reproduces to generate the individuals who will go to winter in Mexico, after a migration of 4000 kilometers. They then gather on the high mountains of the States of Mexico and Michoacán.

Why is the monarch in danger?

According to COSEWIC member Jenny Heron, there are many threats. “There are cumulative effects of pesticides, loss of habitat, loss of their host plant, milkweed,” she explains in an interview with La Presse . There are many factors because of the great range of the monarch. ”

What was the determining factor in the decision?

“The situation in the wintering grounds in Mexico, says M me  Heron. There are fewer and fewer of them. It is indeed in Mexico that it is easier to follow the population of monarchs, and it is in free fall. There are threats to the butterfly there, but the fall of the population is also a reflection of its difficulties elsewhere on the continent. “The size of wintering sites has been reduced,” says Maxim Larrivée. There was deforestation. Sometimes, even if it’s small scale, it affects the microclimate. And with the extreme concentration of the population in “remarkably tiny wintering areas,” as COSEWIC has said, the sharp fall in numbers places the monarch in an even more precarious situation.

“Any species that loses more than 90% of its population runs the risk of extinction,” says Maxim Larrivée, head of research and collections at the Montréal Insectarium.

“In early March 2016, there was an ice storm in Mexico,” says Larrivée. There were 10% immediate losses, but obviously the survivors were weakened because the populations fell to very low levels. ”

What can be done to save the monarch?

The butterfly is already the emblem of the Canada-United States-Mexico Commission for Environmental Cooperation (CEC). This organization, based in Montreal, supports the protection measures, which will necessarily be international in the case of this migratory species. If the monarch is officially added to the endangered species list, Canada will need to adopt a recovery strategy. But we lack data to take action, according to Maxim Larrivée.

“The fall was so fast! Before a recovery program is in place, you have to go back to the field. Breeding areas should be identified. We must create the best network of breeding grounds in Canada, so that our country can do its part, “says Maxim Larrivée, head of research and collections at the Montréal Insectarium.

To this end, the Insectarium team launched, last summer, Mission Monarque, a participatory science program with the general public, which is invited to report the observations of monarch and the presence of milkweed plant On which the butterfly lays its eggs, and which feeds its caterpillars. But the first year of the program reflects the urgency of the species: “We had almost undetectable quantities until the end of July,” says Larrivée.

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2 thoughts on “The Monarch, a species now in peril

  1. Paul Cherubini

    Many exaggerations in the article. Like the claim of a 90% drop in the overwintering population in Mexico over the past 20 years is obviously not supported by this official WWF graph of the population measurements: Also, the goal of conservationists to rebuild the eastern monarch migratory population to its historic average of 6.07 hectares is not realistic nor necessary. Not realistic because it would require thehiring of tens of thousands of workers to successfully re-establshing around 2-3 billion new milkweed stems in wildscape habitat situations around the central and eastern USA and southern Canada. Not necessary because even if there was an 80% storm related mortality event at the overwintering sites in Mexico during an ultra low population year like 2013 (only 33 million butterflies that year) there would still leave 6.6 million surviving overwintered migrants to repopulate the USA in the early Spring. We know that a population of 100,000 – 200,000 surviving overwintered migrants in California are sufficient to repopulate the western USA and British Columbia so 6,600,000 surviving overwintered migrants in Mexico should be more than sufficient to repopulate the eastern and central USA and southern Canada.

    1. Charles Kinsley

      And in southern Ontario, we have plenty of Milkweed plants – likely 100x more than pre-settlement. One problem is that much of the milkweed is next to highways – so many breeding adults and new molts are killed by cars. Of course, there is less milkweed from Kansas south. And planting more milkweed is much sexier than trying to reduce highway traffic and speeds. Or reducing pesticides. Plant more Asclepias from Texas to Kansas and (reduce highway speeds? – fat chance, so really how much do we want to rescue them?)

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