Mexico’s Monarch Butterfly Wintering Grounds

monarch butterflies

Monarch butterflies cluster tightly together in pine and fir trees in their Mexican habitat. (Photo credit: Getty Images)

The number of monarch butterflies overwintering in Mexico dropped by 27 percent in 2017, according to experts. This decline is a reversal in last year’s numbers, which appeared to show a recovery in the monarch butterfly population.

Scientists think this year’s decline was likely caused by a late winter storm that occurred last year. The storm resulted in the loss of more than 40 hectares (100 acres) of forests where the butterflies typically spend their winter months.

“The monarch migration is a phenomenon like no other,” Omar Vidal, CEO of the World Wildlife Fund (WWF) in Mexico said in a press release. “But now, it’s imperiled by forces the monarchs themselves cannot control. The reduction in the area of forest they occupied this year– most probably due to the high mortality caused by storms and cold weather last year–is a clear reminder for the three countries that they must step up actions to protect breeding, feeding, and migratory habitat.”

Scientists estimate that the storms in March 2016 killed approximately 6.2 million butterflies. That number is nearly 8 percent of the total monarch population that overwintered in Mexico last year. Monarch butterflies are typically counted by the area they cover, rather than as individuals. When in their winter habitat, they cluster tightly together in pine and fir forests. This year, the butterflies only covered 2.91 hectares (7.19 acres). This is a significant decline from 2016, in which the butterflies covered an area of nearly 4 hectares (10 acres). However, the 2017 numbers were still significantly higher than the historically low population calculated in 2013, when the butterflies only covered a total of 0.67 hectares (1.66 acres).

“We cannot control the climate, but we can do much better in eradicating illegal logging in the reserve and tackling habitat loss in the U.S. and Canada,” Vidal said. “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 their final orange and black-winged tenant.”

More to Explore
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Monarch Butterfly Migration and Overwintering 
Monarch Watch

Country: Mexico
Location: Mexico is located in North America. It borders the Caribbean Sea and the Gulf of Mexico, between Belize and the United States and borders the North Pacific Ocean, between Guatemala and the United States.
Area: 1,964,375 sq km (land and water) (slightly less than three times the size of Texas)
Climate: The climate of Mexico varies from tropical to desert.
Terrain: The terrain of Mexico features high, rugged mountains; low coastal plains; high plateaus; and desert.
Natural Resources: Copper, gold, lead, natural gas, petroleum, silver, timber, zinc
Economics: $2.307 trillion (est. 2016)
Environmental Issues: Deforestation, deteriorating agricultural lands, desertification, scarcity of hazardous waste disposal facilities; natural freshwater resources scarce and polluted in north, inaccessible and poor quality in center and extreme southeast; raw sewage and industrial effluents polluting rivers in urban areas; serious air and water pollution in the national capital and urban centers along US-Mexico border; widespread erosion
Source: CIA – The World Factbook

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