The population of monarch butterflies wintering in central Mexico is up 144 percent over last year, scientists say.
But that does not mean the butterflies that migrate from Canada and the United States are out of danger.
This winter, researchers found the butterflies occupying 14.95 acres/6.05 hectares of pine and fir forests in the mountains of Michoacan and Mexico states – an increase from 6.12 acres a year ago.
This year’s is the biggest population since the 2006-2007 period, said Andrew Rhodes, Mexico’s national commissioner for protected natural areas. A historic low of just 1.66 acres/0.67 hectares was recorded in 2013-2014.
Jorge Rickards, director of World Wildlife Fund in Mexico which participates in the monitoring, said that there is no guarantee the positive trend will continue.
The first monarchs crossed into Mexico more than a week later than usual, on Oct. 20, because of rain and cold along the Texas-Mexico border, Rhodes said.
“Once in Mexican territory, the butterflies occupied an area that gives us a lot of hope for the future,” Rhodes said.
Scientists said the approximately 15 acres coverage should be seen as a minimum for the viability of the migrating monarchs in the future.
Ryan Norris, an ecology professor from the University of Guelph in Ontario cautioned that the improved coverage in their wintering grounds doesn’t indicate the end of the crisis over butterfly populations.
“It buys us time, but that’s the best it does,” said Norris.
Norris saw little connection between this year’s increase and the conservation efforts, including a crackdown against illegal logging inside the butterflies’ protected area. The uptick had more to do with the weather.
“It was a Goldilocks year this year,” he said. “Not too hot, not too cold, it was perfect.”
Chip Taylor, director of Monarch Watch and an ecology professor at the University of Kansas, agreed.
“It’s not going to be replicated next year, not even close,” Taylor said.
Last spring, cold temperatures north of Texas kept the butterflies there to lay their eggs, but overall warming trends will drive populations too far north.
Loss of habitat, especially the milkweed where the monarchs lay their eggs, pesticide and herbicide use, as well as climate change, will continue to pose threats to the species, scientists still conclude.