Researchers at the University of Guelph have developed a new conservation strategy to help curb the falling population of monarch butterflies that travel across North America.
Ecologist Ryan Norris and Tyler Flockhart, a population biologist and former U of G PhD student, published their findings last month in the journal Current Biology.
“This is a tool for decision-makers who enact conservation policies for this iconic animal,” Norris said in a release.
“This population of monarchs has declined by approximately 80 per cent over the past 20 years, and we need to act fast before we lose them completely.”
In 2023, Canada listed the eastern North American monarch butterfly as endangered, with Mexico listing it as at risk.
The research, which pulled in as much information as possible on the biology and ecology of monarch butterflies, also looked into previous studies. They then combined that with economic and financial information to determine the best way to use conservation funds.
In the study, Norris and his colleagues modelled the best use of $150 million over five years, looking at how and when to spend the money. While such models are used for many applications by scientists, the process proved to have some unique challenges when it comes to monarchs, noted Norris.
“For a species like a monarch butterfly, it’s a complicated problem, because it can occur in different places over its annual cycle,” he said of the migratory insect.
“Because it’s over five years, different decisions can occur in different years. So, it becomes quite a difficult problem to kind of track – you need quite a complicated model.”
To solve this problem, they broke this area where the monarch travels into four different regions. The eastern North American monarch overwinters in Mexico, and then they refer to the three different regions of breeding ground as south, central, and north.
“The north encompasses Ontario and Quebec, so we’re in the northern part of the monarch breeding range. So, we have those four kinds of areas, and then we have the timeframe, and then we have the pot of money.”
All of the variables are then entered into the equation, he explained.
Intending to increase the population of monarchs, they came to focus on restoring milkweed in the U.S. Midwest, which is the central region of their model.
“We’ve lost over a billion monarch milkweed stems over the last few decades, and that’s mainly through agriculture. It’s viewed as a weed, and it’s removed in agricultural areas in the U.S. and Canada, and it’s a host plant to monarchs,” added Norris of the plant.
Norris told The Observer that restoring the milkweed base will not solve all of the issues, but according to their model, it would be the most effective use of funds. The plan would be to spend $30 million a year of the $150 million for the first four years on restoring milkweed in the U.S. Midwest.
“And then the fifth year, there were different options, one of them being to invest money to restore milkweed in the northern part of the breeding range, too, in Ontario, Quebec and some northern states, as well as invest in protecting habitat in Mexico, the overwintering site in Mexico,” noted Norris.
He added that the model can be modified, adjust the timeframe and even some of the proposed steps.
“We could not include all of the potential actions you could do to conserve monarchs, because there are lots of things. But the problem is that we don’t know the consequences of some of those things.”
“For example, one of the things you could do to conserve monarchs is plant native wildflowers in your backyard. But we can’t articulate, at least right now, the effect of that on the monarch population, for every backyard. What does that mean in terms of extra monarchs?”
With the butterflies travelling across three countries, it would be most effective if all three of them cooperated, which would be more economical and efficient than a single-nation strategy.
“There’s a tri-national organization called the Commission on Environmental Cooperation that deals with conservation issues that span the three countries,” said Norris. “And there’s probably no conservation issue that’s more prominent than the monarchs that span the three countries, at least in terms of wildlife.”
