Millions of the butterflies migrates up to 2,800 miles from Canada and the U.S. to Mexico each year and they cluster tightly in the pine and fir forests in the sanctuaries of the Mariposa Monarca Biosphere Reserve in Mexico. Monarch populations are measured by the number of hectares of trees occupied by clustering butterflies. This year that coverage has been estimated at 2.91 hectares, down from last year’s figure of four, which itself was a sharp improvement from the 1.13 hectares in 2014-2015.
However, coverage used to be as much as 20 hectares few decades ago.
Omar Vidal, the head of the Mexico office of the World Wildlife Fund said:
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. It is a clear reminder for the three countries that they must step up actions to protect breeding, feeding and migratory habitat. 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.
It is estimated that the winter storms in March 2016 killed at least 6.2 million butterflies, almost 7.4 percent of the estimated 84 million that migrated to Mexico.
Over the past few decades, monarch populations in North America have decreased by as much as 90 per cent. A recent study predicted that the Monarch butterflies could become extinct within the next 20 years due to multiple factors such as extreme weather, milkweed-killing herbicide use, illegal logging, mining and corruption.
