Worries grow following 'dramatic' drop in monarch butterfly population

It's a trend conservationists are all too familiar with: monarch butterfly numbers across North America have been slowly declining for 15 years.  

But this year's decrease is an even greater cause for concern, with the population of the orange and black butterflies down by more than 50 per cent between the winters of 2019 and 2020. 

"[It's] a dramatic drop," said Rachel Stewart, program manager for Monarch Nation, a program run by the Toronto and Region Conservation Authority (TRCA). 

"Much as efforts to preserve and conserve monarch butterflies are increasing and to provide habitat … it's clear that there's still a long way to go." 

It wasn't always this bleak; between 2018 and 2019 there was an unusual spike, which turned out to be a one-year blip. 

That's why Monarch Nation organized Flight of the Monarch Day Saturday in communities across Canada — events that raise awareness and support the continent-wide effort to stabilize the species' uncertain future. 

Toronto's flagship event took place in Tommy Thompson Park, a narrow peninsula that sits on the waterfront, tucked between Cherry and Woodbine beaches. 

The event marked one of the last opportunities this season to catch a glimpse of a monarch in the city. Viceroy butterflies, which are similar to monarchs but slightly smaller, could also be seen at the park. 

In the coming weeks monarchs across eastern Canada will begin their 5,000-kilometre trek south to Mexico for the winter. 

A new generation of monarchs will then make their way back north next spring.

"They've never been to Canada before so it's kind of neat to know they just instinctively know how to get here," said Stewart.

'We're losing ground every year' 

What's behind the butterflies' declining numbers, Stewart said, is a general loss of habitat mainly caused by farming and urban development. Climate change is also responsible for the dwindling population.

The lack of habitat also means less milkweed, which is the only plant a monarch will lay its eggs on and that caterpillars will eat, she said.

While there are efforts in Canada to help with the planting and preserving of habitats, some of the major habitat loss is happening in the upper Midwest U.S., said Chip Taylor, the director of Monarch Watch, an organization that tracks the migration of monarchs. 

"Unless we're replacing at least [809,000 hectares] of habitat a year, we're losing ground every year," he said. 

That trend is something Toronto Mayor John Tory supports trying to curb. 

In a proclamation signed by Tory Saturday, the city deemed August 22 as "Flight of the Monarchs Day." 

"Pollinators in Toronto and around the globe are under increasing pressure due to habitat loss, climate change, invasive species and pesticides," the proclamation reads. 

"We can all play a role in protecting them."

How can you help? 

If you're interested in helping, there's a couple of different ways to go about it. 

Stewart said planting milkweed is extremely effective — something that wasn't allowed in Ontario until 2014, when the plant was taken off the province's list of noxious weeds.

"There has been an awareness relatively recently that milkweed is the only plant that monarch butterflies will lay their eggs on," she said.

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

Otherwise, if you see a monarch butterfly or milkweed you can submit photos online, which helps scientists track them.

Check out more images of monarchs in Mexico.