The population of monarch butterflies wintering in central Mexico is up 144 percent over last year, experts said Wednesday.
The data presented by Andrew Rhodes, Mexico's national commissioner for protected natural areas, was welcomed but scientists quickly warned that it 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 of pine and fir forests in the mountains of Michoacan and Mexico states.
That's an increase from 6.12 acres a year ago.
They arrive in such numbers that their population is measured by how much surface area they cover.
This year's is the biggest measurement since the 2006-2007 period, Rhodes said.
A low of just 1.66 acres was recorded in 2013-2014.
Jorge Richards, director of WWF in Mexico which participates in the monitoring, cautioned that the butterflies, like other insects, see their annual populations rise and fall and the monarchs have had a declining trend.
Scientists said the approximately 15 acres coverage should be seen as a minimum for the viability of the migrating monarchs in the future.
Loss of habitat, especially the milkweed where the monarchs lay their eggs, pesticide and herbicide use, as well climate change will continue to pose threats to the species.