Scientists say Canadians can make subtle changes to help save the monarch butterfly, after the species’ population declined by 90 per cent in the last 20 years.

A combination of deforestation and storms in Mexico, where the butterflies overwinter, as well as herbicide use in Canada and the U.S., which serves as the species' breeding grounds, has wreaked havoc on the monarch's population.  

University of Ottawa biology professor Jeremy Kerr says Canada must act immediately to prevent the remaining monarch population from disappearing, and Canadians can help. 

"It's a lot easier to save things before they go away, than it is to recover them after they've disappeared," Kerr told CTV Ottawa on Tuesday.

Kerr is a co-investigator on the citizen science project Mission Monarch, which looks at whether the availability of the milkweed plant is affecting the monarch butterfly.

Monarch butterflies need milkweed to lay their eggs, and their caterpillars only eat milkweed plants. But the plant is being wiped out throughout North America, where it's often considered a weed.

Mission Monarch asks participants to visit fields where milkweed  is found over the summer to take note of the number of caterpillars and monarch eggs on the plants. The findings are then submitted on the Mission Monarch website.

Canadians are also being encouraged to leave milkweed in their gardens, and to plant more of it if possible.

"(Monarch butterflies) make our world a little bit more beautiful, and losing that species as part of our day-to-day experience of our own native landscapes seems to me to be a tragedy that we do not need to have," Kerr said.

The information collected on the Mission Monarch website will help scientists and policymakers better protect those areas.

"We just need to make that small, additional effort to do so."

With a report from CTV Ottawa's Joanne Schnurr