Concerned Scientists Seek ESA Protection for Monarch Butterflies

monarch butterfly

Monarch butterfly populations have declined nearly 97% in recent decades. (Photo credit: Getty Images)

Monarch butterfly populations have plummeted in recent decades. As a result, concerned scientists, including those at the Center for Biological Diversity, the Center for Food Safety, the Xerces Society, and monarch scientist Dr. Lincoln Brower, have petitioned the U.S. Fish & Wildlife Service to protect the butterfly species under the Endangered Species Act.

“The Endangered Species Act is the most powerful tool available to save North America’s monarchs,” Tierra Curry, a senior scientist at the Center for Biological Diversity said in a press release about the petition. “So I’m really happy that these amazing butterflies are a step closer to the protection they so desperately need.”

In recent decades, monarch butterfly populations have dropped nearly 97 percent. Studies show that while the monarch butterfly population numbered nearly 1 billion in the mid-1990s, in early 2014, their population was calculated at only 35 million.

The reason for such a drastic drop in butterfly numbers? Scientists point to a similar decline in the number of milkweed plants within the monarch’s habitat. Monarch butterflies depend on milkweed as both a food source and as a place to lay their eggs during their summer breeding months. A study published in 2014 suggests that the decline in milkweed is linked to the increased use of genetically-engineered crops, in particular Monsanto’s Roundup-Ready® herbicide-resistant corn and soybean plants. While the crops can survive repeated dosages of the Roundup® herbicide, the milkweed plants cannot. This is particularly devastating to monarch butterflies, as studies indicate that the butterflies lay nearly four times more eggs per plant on milkweed growing in cropland than in other areas. The increased demand for biofuels has also impacted monarch butterfly populations as their natural habitat is converted to genetically-engineered corn fields to produce ethanol. In total, researchers estimate that the monarch butterfly habitat has been reduced by nearly 70 million hectares (over 170 million acres) in recent years.

Many gardeners and butterfly enthusiasts are trying to help the floundering monarch butterflies by planting milkweed in their yards. Unfortunately, in some cases this is only exacerbating the situation. Many gardeners are planting an exotic tropical milkweed species (Asclepias curassavica) rather than the native species (Asclepias incarnata). Unlike the native milkweed species, the exotic species grows year-round. This means that the monarch butterflies that feed on it do not have to migrate south for the winter. While this may not seem like a bad thing, it turns out that the milkweed also harbors a parasite (Ophryocytis elektroscirrha). If eaten by a caterpillar, the parasite causes wing deformities and a shortened lifespan in the adult butterfly. The parasite is typically not a problem, as infected butterflies normally die during the migration south, preventing its spread to other butterflies. In addition, native milkweed dies off during the winter, which also keeps the parasite in check. However, the parasites can thrive on the non-native milkweed species because it grows year-round. Research published in the Proceedings of the Royal Society B earlier this year indicate that monarch butterflies that overwinter in the United States are 5-9 times more likely to host the parasite than those monarchs that overwinter in Mexico.

monarch butterflies

Monarch butterflies typically spend the winter in the Oyamel fir forests of central Mexico. (Photo credit: Jodi Jacobson/Getty Images)

To help control the spread of infection in non-migrating monarch butterflies, researchers suggest cutting back tropical milkweed twice during the winter. And, wherever possible, they also recommend removing the tropical milkweed and replacing it with a species native to the region, as more and more stores are beginning to stock native seeds.

Loss of habitat in the United States is not the only threat faced by monarch butterflies. Logging also threatens their overwintering habitat in the Oyamel fir forests of central Mexico. A changing climate and extreme weather events, such as droughts and storms also impact butterfly populations. For example, in 2002, a severe winter storm in Mexico killed 500 million monarch butterflies. Monarch butterfly populations have yet to rebound from that extreme event.

According to the petitioners, listing the monarch butterfly as endangered could help put the species on the path to recovery. An endangered listing means that it would be illegal to intentionally kill monarchs or change their habitat without a permit. It would also lead to the designation and protection of “critical habitat” to help recover abundant monarch populations.

“We are extremely pleased that the federal agency in charge of protecting our nation’s wildlife has recognized the dire situation of the monarch,” Sarina Jepsen, endangered species director for the Xerces Society, said in the press release. “Protection as a threatened species will enable extensive monarch habitat recovery on both public and private lands.”

More to Explore
FAQs on the Monarch Butterfly Endangered Species Act Petition
Monarch Butterflies Could Gain Endangered Species Protection
Monarch Butterfly Species Information
Migrating Monarch Butterflies in “Grave Danger,” Hit New Low
Monarch butterflies could get endangered species status
Gardeners’ Good Intentions Are Killing Monarch Butterflies
Monarch Waystation Program 

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