'Alarmingly low' monarch butterfly population calls for international conservation strategy: Guelph professor

To save the "alarmingly low" population of monarch butterflies in North America, a University of Guelph professor and ecologist says Canada, the U.S., and Mexico need to co-operate on a wide-scale conservation plan. 

Ryan Norris and his colleagues have studied monarch butterflies in North America and developed a conservation strategy outlined in a paper recently published in the journal Current Biology.

"In the last 15 years, [monarch butterfly populations have] been at alarmingly low numbers," Norris told CBC K-W's The Morning Edition guest host Josette Lafleur. 

"We really need a conservation plan that we can enact now that's coordinated, and gives us the best return on our investment." 

Monarch butterflies are known for undertaking the longest migration of any known insect species. The butterflies spend the winter in the mountains of central Mexico. Afterwards, they migrate through the U.S. and into Canada, breeding multiple generations along the way. 

The cycle restarts when the offspring that reach southern Canada head back to Mexico around the end of summer.

Role in the ecosystem

Monarch butterflies, like most butterflies, are pollinators, Norris says. Pollinators play an important part in the food chain by allowing pollen-producing plants to reproduce effectively. 

They are also an important food source for a wide variety of animals, which is why Norris says if the butterfly's population dwindles even further, then "we're in big trouble." 

In 2016, the Committee on the Status of Endangered Wildlife designated the monarch butterfly as endangered. Then in 2023, the Canadian government listed the monarch butterfly as an endangered species under the Species at Risk Act. 

These designations were given to the butterfly because of declining populations in North America in the last several years. 

But it's different in the U.S., where the monarch butterfly doesn't have the same designation.

Last December, the U.S. Fish and Wildlife Service proposed that the monarch butterfly be added to the list of threatened species under the Endangered Species Act. As of today, it remains a proposal. 

Wendy Caldwell is executive director at Monarch Joint Venture, a partnership of U.S. federal and state agencies, non-governmental organizations, businesses and academic programs working together to protect the monarch migration across the country.

Caldwell says protocol calls for a public comment period of around one year before a ruling can be finalized. Since the proposed rule was issued in December 2024, Caldwell is anticipating a finalized rule around December of this year. 

With the ruling still pending, she told CBC News they're doing everything in their power including working with "state and federal agencies, non-profits, businesses, communities, and individuals" in conservation efforts.

The proposed strategy

In their study, Norris and his fellow researchers tried to answer the question: "Given a set time frame of five years, and a set pot of money that we can use, what's the best course of action to conserve monarch butterflies?"

Norris' team developed a five-year plan after inputting everything they knew about monarch butterflies and any constraints they identified. The answer the researchers found was simple — restoring milkweed across Canada, the U.S., and Mexico at specific times of the butterfly's annual cycle.

"In the first four years of a plan, the best thing to do is invest money into restoring milkweed, the monarch's host plant, in the U.S. midwest," he said. 

"Then in the fifth year, allocate some of those resources to restoring milkweed in Ontario and the Canadian provinces, and then some resources into protecting habitat in Mexico for their overwintering sites."

Milkweed, as the name suggests, is a type of weed that people and farmers often try to remove from their farms.

However, milkweed is the only food source for the monarch butterfly caterpillars, which is why the conservation plan focuses on planting milkweed in areas where monarchs lay eggs during specific times of the year. 

This strategic investment is something that Donald Davis, a member of the Toronto Entomology Association and chair of the Monarch Butterfly Fund, wholeheartedly agrees with, especially here in Canada.

"[The proposal] is correct to focus on priority areas, which for Canada would include southern Quebec and Ontario," he said. 

Davis has been tagging monarch butterflies since 1967, and continuously since 1985. He says that by focusing on areas where monarchs actually pass through during their migration, it's like getting "the biggest bang for the buck."

Now, despite the proposal focusing on strategic planting of milkweed along the monarchs' migration path, Norris said that pulling off such a plan will still require significant finding — a minimum funding of $30 million a year, or $150 million for five years.

He says the steep price tag is because the plan spans three countries.

International co-operation and co-ordination 

Caldwell says that since the 1980s, the U.S., Canada, and Mexico have been working together to protect monarch populations throughout their migratory range.

She says the Monarch Joint Venture recognizes the reality that the survival of monarch butterflies "depends on healthy habitats across all three countries."

In the U.S., efforts to preserve and improve monarch butterfly populations are taking place across the country, and Caldwell says the Monarch Joint Venture is in the middle of many of these efforts — from conducting community science and research programs to tracking populations and habitat conditions.

"We also engage the broader public in every aspect of this work — from participating in community science to planting native milkweed and nectar plants across backyards, communities, working lands, and larger landscapes," she said.

But trying to coordinate a multi-country conservation plan between Canada, the U.S., and Mexico is more complicated than it looks. 

Norris says there are "some troubling things" happening in the U.S. that's going to prevent conservation efforts from being administered effectively. 

Throughout 2025, the U.S. government has cut billions of dollars in funding from scientific research as part of sweeping cost-cutting measures.

"It's going to set back conservation … a number of decades, unfortunately," Norris said.

Still, Norris believes there is an existing structure for collaboration, referring to the Commission on Environmental Co-operation, which has been around for a number of years. 

LISTEN | Guelph researchers offer $150M plan to save monarch butterflies:

The Morning Edition - K-W7:07Guelph researchers offer $150M plan to save monarch butterflies

Monarch butterflies have been listed as an endangered species in Canada due to the growing decline in their population over the years. Ryan Norris, an associate professor and ecologist at the University of Guelph, says there is a way to save them but it would require the help of the U.S. and Mexico to do so. 

According to the commission's website, its objectives include "facilitating cooperation and public participation to foster conservation, protection and enhancement of the North American environment for the benefit of present and future generations, in the context of increasing economic, trade and social links between the three countries."

"I mean it's not a great time (for collaboration) ... but maybe somewhat ironically, it is a good time at something we can co-operate on and do," Norris said.

What you can do

Davis has good news amidst the monarch's bleak situation. He says many residents of Ontario have shown interest in monarch butterflies, and that they are "already contributing to the population recovery."

Similarly, Norris says he's been seeing more properties planting milkweed and native flowers, which he calls "a really valuable tool to maintain urban biodiversity."

He's urging people to continue doing this because it not only benefits the monarchs, it also benefits other native pollinators. 

This effort seems to be growing across the country. In New Brunswick, several municipalities have put up milkweed plants or gardens. The goal of these gardens is to help "young caterpillars prepare for their more than 4,000-kilometre overwintering journey to Mexico."

Caldwell says a lot more effort is needed to secure a sustainable future for monarch butterflies.

"Expanding large-scale habitat restoration and long-term monitoring — especially on working and public lands — is critical," she said. "Stronger collaboration across sectors and borders is essential, as monarchs rely on healthy habitats throughout their migratory range."

Norris says he believes all countries involved have the ability to do it. 

"Do we have the will to do it? I'm not sure."