No single solution to increase endangered Monarch butterfly population, says expert

Planting more milkweed and rearing monarch butterflies could help dwindling populations, but there are bigger issues with the endangered species.

The reasons for the declining trend in the monarch butterfly population is spread across three different countries — Mexico, the United States and Canada, said Stephen Heard, a biology professor at the University of New Brunswick.

"There is almost never a single magic bullet, there are several different things you might have to do to make sure we always have these super-cool butterflies with us," he said.

He said the monarch butterflies roost together in about a dozen "very small" overwintering areas in central Mexico, which makes them vulnerable to both bad weather events and human disturbance.

Heard said some butterflies that move north feed on milkweed and die due to the use of pesticides in fields. "These are things that are almost entirely our fault."

He said a lack of milkweed — the only food source for monarch caterpillars — is also due to the change in land use. These plants get cleared out of fields, ditches and pond edges making it impossible for monarch larvae to find nutrition, said Heard.

"If we don't have milkweed, we don't have monarchs."

The annual survey published in February by the World Wildlife Fund (WWF) and its partners indicated that the eastern migratory monarch butterflies occupying the overwintering areas in Mexico experienced a significant decline.

"The new data indicates that the species occupied only 2.2 acres during the 2023-2024 winter season, 59% less than the previous year when scientists observed 5.5 acres.," stated the WWF survey.

Many municipalities in New Brunswick have milkweed plants or gardens trying to help the young caterpillars prepare for their more than 4,000-kilometre overwintering journey to Mexico.

The city of Dieppe recently opened its second milkweed garden near its Aquatic and Sports Centre parking lot. A press release noted that the caterpillars can eat up to 200 times their body weight in milkweed before turning into monarch butterflies.

"It was important for us to recognize the role that municipalities can do in protecting endangered species," said spokesperson Alexandre Truchon-Savard.

He said an environmental group called Les Ami.e.s de la nature du sud-est du N.-B., reached out to the city to plant their first milkweed garden on Surette Street last year.

The same group partnered this year and planted the sports centre parking lot garden in late July. Only this time, the city added an artistic sculpture and information plaques to the area.