May 31, 2022 - World

Monarch butterflies see resurgence in Mexico

Many Monarch butterflies are gathered around a tree bark
Monarch butterflies at the Rosario Sanctuary in Michoacán on Feb. 11. Photo: Claudio Cruz/AFP via Getty Images

The embattled monarch butterfly appears to have had somewhat of a royal revival in Mexico.

Why it matters: The butterfly endemic to North America has been at risk for years. Climate change, deforestation, pesticide use and the loss of the milkweed they feed on has made the monarchs' survival much harder.

Driving the news: After years of decline, the area occupied by eastern monarchs in the Mexican forests they flock to grew 35% — from 5.19 acres in December 2020 to 7.02 acres in December 2021 — according to a study from the World Wildlife Fund and the Mexican Committee for Protected Natural Areas released last week.

  • The number of western monarchs nesting in California last year also rose, according to data from the Xerces Society for Invertebrate Conservation.

Yes, but: The monarch is not yet in the clear.

  • Monarch butterflies covered nearly 45 acres of forest in Mexico in the winter of 1995-96, according to the WWF.
  • The number of eastern monarchs has declined more than 70% over the last three decades, while the western population is down 95% since the 1980s, Xerces Society for Invertebrate Conservation warns.

How it works: The monarch is the only butterfly species that makes a two-way migration every year, like birds.

  • Eastern monarchs have particularly long migration periods, heading north to places in the U.S. and Canada for the summer and south to Mexico for the winter. Some have been found to trek over 3,000 miles to escape colder climates. Western monarchs, meanwhile, often travel shorter distances to overwinter in California.

The big picture: The resurgence of the monarch in Mexico last year may signal that the species is adapting to climate change, says Gloria Tavera, a regional director of the commission overseeing a zone that includes the main Mexican monarch sanctuary.

  • Last year, the butterflies left Mexico not in March, as usual, but in February, apparently trying to evade higher summer temperatures north.

What to watch: The U.S. Fish and Wildlife Service will consider whether to add the monarch to the list of endangered species in 2024.

  • The agency in 2020 acknowledged that the monarch meets listing criteria under the Endangered Species Act, but declined to add it, stating other species were in greater danger.

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