The most recent data on the Eastern Monarch butterfly population show that it has fallen to a very worrying level for the resilience of this species, which can be observed in Quebec in the summer season. The federal government has finally classified this butterfly as “endangered”, which should normally lead to the protection of green spaces essential to its survival.
The situation of this highly migratory species, vulnerable to the destruction of its habitat and the impacts of the climate crisis, had already been precarious for several years. But it has just suffered a steep fall of 59% in barely a year.
According to data compiled in particular by the World Wide Fund for Nature on the monarch’s wintering sites in Mexico, the population occupies an area this winter totaling barely 0.9 hectares, compared to 2.21 hectares last year. As it is impossible to count butterflies one by one, inventories are carried out by evaluating the space occupied by all the individuals.
For comparison, to hope to have a monarch butterfly population that is “resilient”, it would have to occupy an area of at least six hectares, specifies the director of the Montreal Insectarium, Maxim Larrivee. This would represent a population of 125 million to 130 million butterflies.
This year, with an area of 0.9 hectares, it is estimated that the population barely reaches 15% of the number that would be desirable to ensure its survival. Already, for around twenty years, we have noted that monarchs occupy on average three hectares in their wintering area, which was already insufficient. “Since the beginning of the 2000s, the monarch butterfly has not been able to regain a sufficient population size to hope to have a form of resilience that would allow the migratory phenomenon to continue in the long term. This is what is worrying,” summarizes Mr. Larrivee.
Environmental pressures
“The species faces different environmental pressures throughout its life cycle, including warming and extreme climate events, but also the loss of breeding habitats in summer. The number of milkweeds, which are essential plants for the caterpillar to feed on, has declined significantly due to monoculture and the use of herbicides. These practices have a huge impact on reproductive capacity,” explains the specialist.
In southern Quebec, for example, agricultural activities have eliminated several habitats crucial to the survival of the species. Urban sprawl and industrial development have also eradicated green spaces suitable for milkweed, a plant on which the butterfly lays its eggs.
Faced with the marked decline of the species, the Trudeau government decided last year to support the opinion of the Committee on the Status of Endangered Species in Canada, which had recommended in 2016 that the lepidopteran receive this designation, the most severe status provided for by the Species at Risk Act before that of “extinct” species in the country.
Now that the species is so designated, the federal government must normally implement a recovery plan which involves protecting its “critical habitat” on Canadian soil. Is this the government’s intention? “The monarch butterfly is an important pollinator, essential to the production of many crops in Canada. Pollinators are the basis of our food security, our health and our quality of life. We remain determined to ensure the protection and survival of this emblematic species,” responded Thursday the office of the federal Minister of the Environment, Steven Guilbeault.
“The Government of Canada is committed to protecting and recovering Canada’s species at risk through conservation measures based on sound science, partnerships and rigorous recovery planning,” adds Environment and Climate Change Canada in a written response.
Critical habitat
Several habitats could be designated in Quebec, including the “field of monarchs”, land owned by Transport Canada, but leased “long term” to Aéroports de Montréal and located very close to the Pierre-Elliott-Trudeau airport. The organization Technoparc Oiseaux has been campaigning for several years for the protection of the sector, which was the subject of cuts that mowed down many milkweed plants in the summer of 2022.
For the director of the Montreal Insectarium, there is an urgent need to protect “areas with high reproductive potential”, but also land that is fallow or that could be restored in order to encourage the presence of the endangered butterfly. “We should therefore increase fallow areas and protect green spaces with milkweed,” underlines Maxim Larrivee.
The butterfly’s complex life cycle, however, means that efforts to protect the species must extend beyond Canadian borders to the United States and Mexico. For example, in the southern United States, females lay their eggs on the leaves of milkweed, a variety of plants that is becoming increasingly rare due to the use of herbicides and the omnipresence of monocultures. This factor seriously harms the development of monarch caterpillars. The entire renewal of the species suffers.
Adult butterflies that overwinter in Mexico reproduce the following spring. The monarchs then migrate north to arrive in Quebec in June, where they also breed. Several generations of monarchs can follow one another before these butterflies reach our regions, then leave for Mexico at the end of summer.
Monarch populations have collapsed in recent years in North America. The Eastern population has suffered an 85% drop, but the situation of the so-called “Western” population is even worse: it has gone from 1.2 million butterflies in 1997 to less than 30,000 today. today.