Monarch butterflies winter migration falls
Winter migration of monarch butterflies to Mexico dropped after one-year recovery. Experts believe the decrease was caused by late winter storms last year that knocked out more than 40 hectares of trees, more than four times the amount lost to illegal logging.
The number of butterflies wintering in Mexico dropped by 2017 compared to 2015 says a study released by the government and independent experts. They are counted not by the number of individuals but the area they cover.
“The reduction in the area of forest they occupied this year is most probably due to the high mortality caused by storms and cold weather last year,” said Omar Vidal, the head of the Mexico office of the World Wildlife Fund (WWF). “It is a clear reminder for the three countries that they must step up actions to protect breeding, feeding and migratory habitat.”
Millions of monarchs migrate from the US and Canada each year and cluster in the pine and fir forest of Mexico City. Officials estimate the storms in march killed about 6.2 million butterflies form the 84 million that wintered in Mexico, said Alejandro Del Mazo, Mexico’s commissioner for protected areas. It caused the biggest storm related loss since 2009-2010 when rainstorms and mudslides caused the loss of 106 hectares.
Monarchs depend on finding well preserved forests that help protect them from cold rains and steep drops in temperature. For this, the fight against illegal logging continues. Also, the loss of milkweed has affected the species. The use of herbicides in the US and Canada has decreased their food supply.
The combination of the storms, the lack of milkweed and forest’s loss proved to be devastating with butterflies only covering 2.9 hectares this year.
“We cannot control the climate, but we can do much better in eradicating illegal logging in the reserve and tackling habitat loss in the US and Canada,” said Vidal. “But even if Mexico’s overwintering sites never lose another tree, without food and habitat along the migration routes, the forests will soon bid farewell” to the monarchs.