More than six million monarch butterflies were killed in a single month in Mexico, showing an increasing need "to protect breeding, feeding, and migratory habitat," says a rep for the World Wildlife Fund. Experts who count the butterflies that migrate from the US and Canada to Mexico each winter say the insects covered about 10 acres in Mexico last winter. This December, they covered 7.2 acres—a loss of 27%, reports Reuters. Experts say about 6.2 million butterflies, or 7.4% of the population in Mexico at the time, were likely killed when winter storms hit in March 2016, just as the butterflies were preparing to fly north, per a release. The storms brought rain and high winds that toppled 133 acres of butterfly habitat.
It was the biggest forest loss in six years. However, experts say the loss of forests, also due to illegal logging, isn't the sole reason for the population decline. Milkweed, necessary food for monarchs, is becoming scarce in the US and Canada with less open land and increasing use of herbicides. "Even if Mexico's overwintering sites never lose another tree," the butterflies could soon disappear unless humans do more to prevent illegal logging and habitat loss, says a World Wildlife Fund rep. Referring to President Trump's promised wall on the US-Mexico border, however, an environmentalist says there are fears there will also be "an environmental wall" if environmental cooperation between the two countries ceases, "and that its first direct victim might be the monarch butterfly." (See why monarchs are a "biological treasure trove.")