Migrating Monarch Butterfly Numbers Are At A Record Low

[ Watch the Video: Where Have All The Monarchs Gone? ]

April Flowers for redOrbit.com – Your Universe Online

A new report, based on a December 2013 survey of Mexico’s Monarch Butterfly Biosphere Reserve, claims that migrating monarch butterflies are in “grave danger.” The butterfly colonies currently occupy the smallest area since records began in 1993.

The butterflies spend their winter hibernating in the forest of the reserve. In December 2013, the butterflies only occupied 1.65 acres. National Geographic reports that this represents a 44 percent drop from 2012 when they covered 2.76 acres of land. Additionally, the Associated Press (AP) reports that at the peak of recorded populations, the butterflies covered more than 44.5 acres in 1996.

Monarch butterflies are found in many parts of the world, including North and South America, Australia, New Zealand, and many South Pacific Islands. The most studied subspecies, however, is the migratory monarch, since it is the group at most risk.

“The monarch butterfly as a species is not endangered. What is endangered is its migratory phenomenon from Canada to Mexico and back,” noted Omar Vidal, director of WWF-Mexico, in an email to National Geographic reporter Christine Dell’Amore.

There are a few reasons  why migrating monarch numbers are falling: widespread loss of a plant called milkweed, which their young rely on for food; extreme climate fluctuations in North America, including freezing temperatures and heavy rain; and deforestation. The loss of these populations could spell disaster for many ecosystems because monarchs pollinate plants, including corn, that humans rely on for food.

Researchers have been seeing this decline for the past three years. “Data from previous time periods usually show a pattern of ups and downs,” Karen Oberhauser, a monarch expert at the University of Minnesota in Minneapolis, told Dell’Amore. Oberhauser worries the survey may be underestimating the population loss.

The monarch butterfly weighs in between 0.0095 to 0.026 ounces. The most noteworthy aspect of the insect, however, is the annual migration. Every autumn, millions of butterflies head south and west from Canada and the US, headed to Mexico. They stop at sites along the way to breed and feed. The butterflies who migrate one year are not the ones who arrived in Mexico the year before. The migration covers thousands of miles, and spans five generations of butterflies to complete.

Most adult butterflies live only one month. The fifth generation, however, are different. They live approximately seven to eight months, which is just enough time to make the trip from Canada or the US to central Mexico where they hibernate in the Mexican states of Michoacan and Mexico. These hibernation grounds were discovered in 1976 by Dr. Fred A. Urquhart and a team of volunteers.

Milkweed is a necessary ingredient in the monarch’s lifecycle and migration. It is the only plant they will lay their eggs on, and the newly hatched larvae eat the plant as their first meal.

The problem is that milkweed is not popular with farmers and ranchers because it is poisonous to livestock. The weed was once widespread throughout the United States, but today it only holds 58 percent of its historical range due to herbicide use, especially on corn and soybean fields.

According to AP reporter Mark Stevenson, Lincoln Brower, a leading entomologist at Sweet Briar College in Virginia, wrote that “the migration is definitely proving to be an endangered biological phenomenon.”

“The main culprit,” he wrote in an email to Stevenson, is now genetically modified “herbicide-resistant corn and soybean crops and herbicides in the USA,” which “leads to the wholesale killing of the monarch’s principal food plant, common milkweed.”

The butterflies are also threatened by climate extremes, such as the droughts, heat waves, and storms that have hit North America in recent years. Monarch numbers were very low in 2005 and 2006, which has been attributed to a severe drought in the US.

The final threat to the butterflies is logging, both in Mexico and the US. Loss of habitat on both ends of the migration is squeezing the population into smaller and smaller areas.

Oberhauser said there are ways to halt the decline by recruiting the help of all three North American countries, although she admits this will not be easy.

She notes that one strategy would be incorporating milkweed into large scale plantings wherever possible—including marginal lands like roadsides.

Gardeners in North America can also contribute to conservation efforts by planting milkweed and making their gardens more butterfly-friendly.

“Given the conservation challenges facing monarchs, it’s vitally important that we mobilize as many people as possible,” Oberhauser said. “Through our collective efforts, monarch populations can rebound, so that their migrations may be appreciated by many generations to come.”

The survey’s results were announced shortly after the 20th anniversary of the North American Free Trade Agreement (NAFTA), in which Canada, the US and Mexico signed environmental accords to protect migratory species such as the monarch. The butterfly was adopted as the symbol of the trilateral cooperation.

President Obama is scheduled to visit Mexico on February 19, with events in Toluca, a city just a few dozen miles from the butterfly reserve.

“I think President Obama should take some step to support the survival of the Monarch butterflies,” writer and environmentalist Homero Aridjis, who has been a lifelong proponent of the monarch, told Stevenson. “The governments of the United States and Canada have washed their hands of the problem, and left it all to Mexico.”

Mexico’s National Commission for Protected Areas collaborated in the survey with World Wildlife Fund (WWF) Telcel Alliance.