Disponible en français : Mise à jour – Le monarque : un emblème en péril
The monarch butterfly, one of Canada’s iconic species, is facing an imminent risk of extinction.
In 2016, the Committee on the Status of Endangered Species in Canada (COSEWIC) assessed the species as endangered. Meanwhile, a recent American study suggested there is a substantial probability that the monarch butterfly will become quasi-extinct – that is, there will be too few to repopulate – within the next 20 years.
The monarch butterfly is a migratory species. Over the course of multiple generations, monarch butterflies travel thousands of kilometres to and from their wintering grounds in the mountains of Mexico or southern California (Figure 1). The monarch faces threats throughout its range, requiring the combined efforts of three nations for its recovery.
Source: Map adapted from Environment Canada, Species at Risk Public Registry, Management Plan for the Monarch (Danaus plexippus) in Canada – 2014 [Proposed], Figure 3.
Population on the decline
Monarch butterflies that spend time in Canada are divided into two populations based on whether they live west or east of the Rocky Mountains. The western population hibernates in California, while the larger eastern population overwinters in the forests of Mexico. Small resident monarch butterfly populations also occur in southern Florida.
Measurements of monarch butterfly populations are taken during the hibernation period. In Mexico, the area of forest occupied by the eastern population of monarch colonies during their hibernation is used as an indicator of the number of butterflies arriving from Canada and the United States each year.
As Figure 2 illustrates, this area can vary significantly, but has generally decreased since the 1990s. According to some sources, the population has declined about 80% over the last decade. Volunteer-reported data from California suggest that the western population has also declined considerably – by 74% since the 1990s.
Note: The measurement is taken in December of each year.
Source: Figure prepared by the authors using data obtained from MonarchWatch.org, Monarch Population Status, 11 February 2017.
Loss of habitat a key contributor
COSEWIC identifies a number of issues that contribute to the declining monarch population. In particular, loss and degradation of habitat at overwintering sites – in large part the result of illegal logging in Mexico and real estate development in California – are key factors. Thinned forest habitat in Mexico exposes overwintering monarchs to adverse weather conditions, which has resulted in mass mortality.
Another factor is the widespread use of pesticides and herbicides across North America. The use of genetically modified crops (Roundup Ready) has increased spraying in areas known to support milkweed. Milkweed is critical breeding habitat for monarchs since their larvae feed exclusively on this plant.
However, some researchers believe that the monarch population decline is linked to diminished success in fall migration at a point after monarchs rely on milkweed. Factors such as a lack of nectar sources and habitat fragmentation may play a role in population declines.
Government initiatives: Examples from Canada, the United States and Mexico
In Canada, the management of habitat critical to monarchs falls mostly under provincial jurisdiction. Various provinces have programs to manage and conserve monarch populations. However, the federal government plays a role in monarch conservation through its responsibility for international affairs and its power to enter into international agreements.
The federal government also promotes coordination of conservation activities among the various levels of government; it conducts scientific research and provides funding and technical expertise in support of monarch conservation.
In the fall of 2017, COSEWIC will submit its latest assessment of the monarch’s status to the Minister of Environment and Climate Change. If, based on this assessment, the government decides to change the status of the species and list it as endangered, the government will be required to propose a recovery strategy within one year. One or more action plans based on a recovery strategy will then be required under the Act.
The monarch is not yet protected under the U.S. Endangered Species Act. However, as a result of a 2014 petition, the U.S Fish and Wildlife Service is currently conducting an assessment. A decision on listing is due in June 2019.
In February 2015, the Service announced a $3.2-million allotment toward efforts to conserve the monarch. The Monarch Joint Venture is a partnership of federal and state agencies, non-governmental organizations, and academic programs working in a coordinated manner to protect the monarch migration across the lower 48 American states.
In Mexico, hibernation sites have been protected as various forms of wildlife reserves since the 1980s. The Monarch Butterfly Biosphere Reserve, created in 2000 and recognized as a world heritage site in 2008, covers more than 560 square kilometres.
Enforcement actions by the Mexican government have reduced illegal deforestation on the reserve. Meanwhile, multiple public and private efforts to create better economic conditions in the region have decreased local incentives to harvest the forest illegally. In June 2016, President Peña Nieto stated his country’s goal of expanding the monarch butterfly’s wintering ground in Mexico from 4.1 to 6 hectares by 2018.
As for trilateral initiatives, a North American Monarch Conservation Plan was released by the Commission for Environmental Cooperation in 2008. In March 2014, the Prime Minister of Canada and the presidents of the United States and Mexico issued a joint statement announcing the creation of a working group to ensure the monarch’s conservation.
Authors: Penny Becklumb and Tim Williams, Library of Parliament