March 15th, 2013 by
Monarch butterfly

Monarch butterfly. Credit: William Warby

What’s black and white and orange all over? Probably many things, but I’m thinking specifically of the monarch butterfly. Why? Because earlier this week, Mexico’s National Commission of Natural Protected Areas announced that the wintering population of the monarch butterfly declined by 59 percent this winter. The monarch — which can’t be counted individually, but whose population is measured instead by the amount of canopy covered while they are huddled together in the winter for warmth — occupied more than seven acres last winter and less than three acres this year.

This year’s figure represents the lowest number of butterflies in Mexico in the last two decades, when record keeping began, and the third year of declines. Lincoln Brower, a leading entomologist at Virginia’s Sweet Briar College, tells the Associated Press (AP) that “the report of the dwindling monarch butterfly winter residence in Mexico is ominous. This is not just the lowest population recorded in the 20 years for which we have records. It is the continuation of a statistically significant decrease in the monarch population that began at least a decade ago.”

For years, the monarch’s winter home in Mexico has been threatened by deforestation. At a peak in 2005, logging consumed more than 1,100 acres of areas in Michoacán, Mexico, where the butterfly winters. A year later, American Forests began work to restore oyamel firs in Michoacán to benefit the monarch; we’ve helped plant a million trees for the monarchs since 2006. The AP reports, though, that aerial surveys in 2012 revealed little logging in the monarch’s home, which has left some researchers looking at another culprit for the monarch’s decline: U.S. herbicide use.

Milkweed

Milkweed. Credit: Jerry A. Payne, USDA Agricultural Research Service, Bugwood.org

During the migration from its summer homes in the northern U.S. and southern Canada to Mexico and back again, the monarch relies on milkweed growing throughout America’s agricultural fields for sustenance. However, herbicide-resistant crops have meant more herbicide use, which means very little milkweed peeking up between rows of corn and soybeans. Add in drought, and there are a lot of missing food sources for the monarch.

Chip Taylor, director the University of Kansas’ Monarch Watch, tells The New York Times that the butterfly migration is at a tipping point. If numbers continue to decline, the butterfly may not be able to readily recover from a natural disaster, such as an extremely harsh winter in Mexico.

The magnificent migration of the monarch butterfly is a wondrous, natural marvel, and its current precarious state is a prime example of how interconnected our natural systems are. Animals, insects, plants and trees flow from one ecosystem and habitat to another more rapidly than we sometimes realize. That’s why we’re focused not only on trees, but on the forests overall. If we protect them, we protect so much more.