Monarch butterfly population rebounding after record low

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 (1.65 acres) in the pine and fir forests west of Mexico City.

• Monarch butterfly numbers drop to new lows

But even if the number of butterflies triples, they would cover only about 2 hectares (5 acres). That would be just over one-tenth of the record high of 18.2 hectares (45 acres) 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 amount of acreage they cover.

The same generation never lives to make the round trip to summer habitats in the United States and Canada.

• Watch 'The Great Butterfly Hunt' on CBC's The Nature of Things

No small-scale logging in butterfly habitat

More good news came from the annual survey 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 (33,482-acre) core zone had no small-scale logging, the kind that happens when indigenouscommunal farmers cut trees for their own use.

The communal farms own most of the property in the reserve.

"This demonstrates the commitment of the land owners," Vidal said. The indigenouscommunities receive government support to conserve the forests, and they make some money from reforestation projects and tourists who come to see the butterflies.

However, Vidal noted there had been an outbreak of commercial logging in one mountain community, where about 5.2 hectares (13 acres) of trees were cut. Drought killed off nearly threehectares (7.41 acres) of trees, for a total loss of forest cover of about eight hectares (20 acres) in the reserve. That is down from 16.6 hectares (41 acres) 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."