Conservation efforts to protect the eastern North American monarch butterfly for future generations will require a coordinated effort between Canada, the United States and Mexico, according to new research published by Dr. Ryan Norris, ecologist in the Department of Integrative Biology and Dr. Tyler Flockhart, a population biologist and former PhD student at the University of Guelph.
In collaboration with an international group of colleagues, Norris and Flockhart developed a conservation strategy outlined in a paper recently published in Current Biology.
"This is a tool for decision-makers who enact conservation policies for this iconic animal," Norris says. "This population of monarchs has declined by approximately 80% over the past 20 years and we need to act fast before we lose them completely."
The analysis shows that a coordinated $30-million annual investment over five years ($150 million total) is required. "Our work demonstrates how population data can be combined with financial resources to develop optimal solutions for conserving migratory species that cross international borders," Norris says. Similar methods have been used in conservation efforts around the world, but never with migratory species.
The migration of the eastern North American monarch butterfly is witnessed by millions of people across three countries each year. Monarchs over-winter as adults in the highlands of central Mexico and then, over successive generations, repopulate the U.S. and Canada each spring and summer.
The last generation in the late summer then migrates back to the same small area in Mexico and the cycle begins again. Since monarchs do not observe geographic or political boundaries, developing effective conservation strategies for this long-distance migrant creates special challenges that require all three nations to work collaboratively.
The analysis conducted by Norris and colleagues addresses how to best allocate resources toward habitat protection and restoration across the three countries. "Our work demonstrates that the real hotspot is for milkweed, the monarch host plant where they lay eggs, to be restored in the U.S. Midwest," Flockhart says.
In the U.S., 1.5 billion milkweed plants have been lost since 1999. "It's an agricultural weed, so it's removed from agricultural fields because it reduces yield for farmers," Flockhart explains.
Monarchs are spotted throughout southern Ontario from late spring until late September. They feed on flower nectar, transferring pollen between flowers, enabling the production of plants, seeds and fruits, and are a food source for other animals, birds and insects.
In 2023, Canada listed the eastern North American monarch butterfly as endangered under the Species at Risk Act and Mexico has listed them at risk. The U.S. currently has no legislated protection for the species.
While a single-nation strategy is also an option, Norris and Flockhart say such an approach would be less effective than the more economical and efficient tri-national strategy, as evidenced by their results.
