Room for Monarch butterflies to grow

The survey from the World Wildlife Fund in Mexico show the numbers on the mend, but the population is still well below a high in the 1 billion range two decades ago. The monarch’s recent comeback is due to favourable weather and the planting of more milkweed, an important plant to keep numbers up on its migration route, the survey said. 

“Today’s news provides a hopeful indication that we are helping them head in the right direction and curbing the loss of this magnificent butterfly.,” said Sylvia Fallon, a senior scientist at the Natural Resources Defence Council. 

The study found they have suffered mightily over the years from the expansion of farmland, sprawling housing developments and the clear-cutting of natural landscapes along their migration path, experts say.

Monarchs lay eggs only on milkweed plants, which grow wild throughout the United States. But the milkweed, on which their larvae feed, can cause stomach problems for cattle that eat it, so ranchers and farmers destroy it, researchers said. The butterflies congregate in Mexico and then go through several generations as they fly north on their long migration to Canada. 

Their plight has become an international issue. In February 2014, the United States, Mexico and Canada agreed to set up a joint task force to protect the butterflies. While an estimated 1 billion monarchs migrated in 1996, only about 35 million made the trip in 2013, according to Marcus Kronforst, professor University of Chicago.