Extreme weather threatens butterfly migration

Heavy storms earlier this year hammered the forests that North America's monarch butterflies migrate to in central Mexico, a study showed on Tuesday, fueling fears the habitat could eventually become untenable.

Conservationists said storms and strong winds in March uprooted more than 20,000 trees in Mexico's Monarch Butterfly Biosphere Reserve, which lies west of the capital on the border of the states of Mexico and Michoacan.

Nearly 54 hectares of the core of the reserve were hit, the most significant impact since storms during the 2009-10 season ravaged more than 100 hectares, said Omar Vidal, director-general of the Mexican arm of the World Wildlife Fund.