‘Light recovery’ in monarch butterfly population predicted
Oct 06, 2014
Experts in Mexico say deforestation is down in the forest that is the winter home of monarch butterflies.
- Mexico’s World Wildlife Fund says commercial logging remains a threat in the area where monarch butterflies spend the winter.
MEXICO CITY—Deforestation is down in the Mexican forest that is the winter home of monarch butterflies, and scientists also hope to see a rebound in the annual migration after it fell to historic lows last year, an expert said Thursday.
Omar Vidal of the World Wildlife Fund said two to three times more monarchs may arrive this year, compared to last year.
“The data from the United States indicates a light recovery,” Vidal said. “They are calculating that we can expect at least double the number and perhaps triple.”
Last year, the monarch population dropped to the lowest level since record-keeping began in 1993, covering just two-thirds of a hectare in the pine and fir forests west of Mexico City.
But even if the number of butterflies triples, they would cover only about two hectares, down from a record high of 18.2 hectares in 1996-97.
Millions of the black-and-orange butterflies return to a reserve area each winter, clustering in trees in numbers so great that they are counted not as individuals, but by the area they cover.
The same generation never lives to make the round trip to summer habitats in the United States and Canada.
More good news came from the annual survey that experts perform using satellite photos and on-the-ground reconnaissance to check on tree cutting in the reserve.
Logging threatens the butterflies because it pokes holes in the canopy of fir trees that protect them from cold weather and freezing rains.
This year, Vidal said the reserve’s 13,550-hectare core zone had no small-scale logging, the kind that happens when Indian communal farmers cut trees for their own use.
The communal farms own most of the property in the reserve.
However, Vidal noted there had been an outbreak of commercial logging in one mountain community, where about 5.2 hectares of trees were cut. Drought killed off nearly three hectares of trees, for a total loss of forest cover of about eight in the reserve. That is down from 16.6 hectares of tree loss last year.
Vidal said concerns remain about the destruction of milkweed — the plant on which the butterflies lay their eggs — in the United States and Canada. The three countries formed working groups this year to confront problems facing the butterflies, but Vidal said that “in reality, we have not seen concrete actions in the United States and Canada.”
Meanwhile, a surprising study suggests the species itself also started out in North America some two million years ago.
Researcher Marcus Kronforst of the University of Chicago said monarchs were widely thought to have evolved in South or Central America. But DNA from 80 monarchs sampled from the Americas and as far away as Europe and Australia points to a North American origin, maybe in the southern United States or northern Mexico.
Kronforst also said scientists had thought the monarch arose from a non-migrating ancestor. But the new study concludes the ancestor did migrate.
The study was released Wednesday by the journal Nature.