One of the greatest migrations in the world features a fragile and beautiful creature, the monarch butterfly. The butterflies' epic journey of more than 2,500 miles takes four generations of butterflies to complete every year, and they return to the same sites, sometimes even the exact same trees, each winter. It is one of the most dazzling of mass migrations, and has brought tourists to sanctuaries in Mexico to gasp in wonder as the butterflies gather in the millions. But, scientists fear that this spectacle may be disappearing because fewer of the butterflies than ever are making it to their wintering destination. In fact, this year has seen the lowest count in more than a decade.

monarch butterfly cluster

The monarch butterfly population in Mexico was the lowest ever since 1993 (the year scientists started to monitor monarch butterfly colonies), according to research just released by the WWF-Telcel Alliance and the Monarch Butterfly Biosphere Reserve Office of the Mexican government. "The research shows a 43.7 percent decrease (nearly three acres) in the total amount of forest land occupied by monarchs in and near Mexico’s Monarch Butterfly Biosphere Reserve. The research was conducted over several weeks in December 2013 and the decrease is in relation to December 2012 research," writes the World Wildlife Fund. The problem is one that multiple nations must work together to fix, as the monarch migration spans the United States, Canada and Mexico.

The species is already considered near threatened. The main reasons for their decline have been the continued loss of habitat used for over-wintering through deforestation, a loss of their food source of milkweed to farmland and rampant weed killer, and severe weather conditions like cold snaps and droughts. With these factors hitting at the same time over many years, monarch butterflies are in a dramatic downward spiral.

monarch butterflies mating

In its report, WWF points out that Mexico has been effective in protecting the Monarch Reserve, where most monarchs spend the winter, so the main contributor to the decline of monarchs today is the loss of milkweed due to herbicides and the growth of herbicide-resistant corn and soy crops in the Midwest of the U.S. between 1999 and 2010. Without milkweed as a food source, monarch caterpillars have little chance of survival. 

monarch butterfly clump

Lincoln Brower, a leading entomologist at Sweet Briar College in Virginia, told the Huffington Post that "the migration is definitely proving to be an endangered biological phenomenon."

"I think the monarch is the canary in the coal mine telling us that things are beginning to go really wrong, when you can take a widespread migration of this sort and completely dismantle it as a result of human activity," he told The Washington Post in an interview about the species' decline.

Though it's possible for the monarch butterfly to recover from such a loss, all factors need to be in their favor for years — a return of milkweed plants in the U.S. landscape, protection of existing wintering sites and replanting lost habitat, and the least controllable of all, decent weather along their migration routes. While some people have high hopes, some scientists including Brower have their doubts that it is possible for the species to bounce back.

"It's unclear what would happen to the monarchs if they no longer migrated. The butterflies can apparently survive year-round in warmer climates, but populations in the northern United States and Canada would have to face bitter winters. There is also another small migration route that takes the butterflies to California, but that has also registered declines," according to the Huffington Post.

If you are interested in learning more about protecting the monarch butterfly and preserving one of the world's most spectacular migrations, check out Monarch Watch, an organization with tons of information about how to help.

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