PIEDRA HERRADA, Mexico—The number of monarch butterflies reaching their wintering grounds in central Mexico this year may be three to four times higher than the previous season, authorities said on Thursday.
Speaking during a visit to a monarch reserve with US Interior Secretary Sally Jewell, Mexican Environment Secretary Rafael Pacchiano said initial reports suggest the butterfly population is rebounding.
“We estimate that the butterfly population that arrives at the reserve is as much as three and could reach four times the surface area it occupied last season,” Pacchiano said.
He did not explain how the government made the calculation, but authorities conduct informal tracking of monarch butterflies as they enter Mexico from the US.
The population of orange-and-black butterflies making the 5,500-kilometer migration from the US and Canada declined in recent years before recovering slightly in 2014, when the insects covered about 1.13 hectares in the mountains west of Mexico City.
The monarchs cluster so closely in trees that their numbers are measured by the area they cover. They once blanketed as much as 18 hectares. Pacchiano said the butterfly colonies could cover 3 hectares or 4 hectares this year, and officials hope to reach 6 hectares in the reserves by 2020.
“The US is very committed to protecting the monarch butterfly, but we need the help of Mexico and Canada,” Jewell said before hiking an hour into the mountains to see the trees where the monarchs roost.
She added that the US is working to reintroduce milkweed, a plant key to the butterflies’ migration, on about 3 million hectares within five years, both by planting and by designating pesticide-free areas.
Milkweed is the plant the butterflies feed and lay their eggs on, but it has been attacked by herbicide use in the US.
“Our agricultural practices must be adapted…. We have to look at our use of pesticides,” Jewell said. “We have the goal of 225 million monarch butterflies returning right here, to Mexico, every year. We believe we can get there by working together.”
Mexico, too, still has problems.
Illegal logging more than tripled in the monarch butterflies’ wintering grounds last year, reversing several years of steady improvements. Pacchiano said the reserve’s buffer area lost more than 9 hectares due to illegal logging in one area this year, but the tree cutting was detected and a number of arrests were made.
Loggers cut down 19 hectares of trees in San Felipe de los Alzati in Michoacan state last year, the biggest loss since 2009.
Image credits: AP/Rebecca Blackwell