This blog post was originally published by Columbia Science Review in April 2015.
By Alexandra L. DeCandia
Monarch butterflies are an iconic American species. Found in all 50 states, these orange-and-black backyard visitors delight children with their delicacy and grace. They pass through our gardens each year, participants in an annual, multi-generational migration among the farthest undertaken by an insect species. Traveling south from Canada and the United States, eastern monarchs traverse over 3,000 miles to reach warmer climes in the Sierra Madre Mountains of Mexico.
In the past two decades, North American monarch populations have plummeted. Once covering 20.97 hectares of overwintering habitat in 1996-1997, monarchs occupied a meager 0.67 ha in 2013-2014. This is a 97% decline in occupied land area. A staggering statistic, such losses are cause for concern. Some scientists and activists promote monarch butterfly protection under the United States Endangered Species Act. They argue that while species eradication is unlikely, we risk the loss of an incredible migratory event unparalleled on our continent.
Before concrete conservation action can be implemented, it is crucial to ascertain the cause of these declines. According to a series of emails I received from Environment New York, “Monsanto is driving the monarch butterfly to the brink of extinction.” The subject merely reads: “Monsanto killing butterflies.” I found myself wondering “How?” but, more importantly, “Why?” The phrasing of these emails connoted a sense of malicious intent behind the actions of this controversial agricultural company. I imagined a group of nefarious individuals--executives, scientists, large-scale farmers—laughing maniacally as they ripped wings off butterflies amid a shower of money and herbicides pouring from the sky. This is hardly the reality of the situation.
The real impetus behind Environment New York’s campaign against Monsanto rests in the reduction of common milkweed (a weed species commonly found in corn and soybean fields) as a direct result of herbicide use on genetically modified crops. Common milkweed is the preferred food source of monarch butterfly larvae. Migrating adults lay their eggs on plants interspersed throughout the Midwest every year. Farmers consider the plant a major pest species, however, as it reduces overall agricultural yields. They have always employed herbicides to decrease milkweed populations in their fields, but use of the most potent herbicide, glyphosate or RoundupTM (Monsanto), was previously limited due to its negative effects on crops. In the 1990s, Monsanto introduced genetically modified, glyphosate-tolerant corn and soybean plants to agricultural markets. By 2011, adoption of these crops reached 72% and 94%, respectively. Use of Roundup skyrocketed. Unsurprisingly, common milkweed populations crashed.
Without common milkweed plants to feed their larvae, monarch butterflies were unable to adequately propagate their populations. The ever-increasing adoption of Monsanto’s Roundup ReadyTM crops during the past two decades matched increasing instances of monarch declines almost perfectly. It is important to note that the loss of milkweed is not the only stressor currently affecting monarchs. Extreme weather events (notably temperature fluctuations and changes in precipitation) associated with climate change and the loss of overwintering habitat at the hands of illegal loggers are also implicated in monarch declines. The stressors work synergistically. Evaluation of each factor’s relative impact on declines of butterfly populations, however, revealed that milkweed loss remains the primary cause. It appears Monsanto is killing butterflies.
On March 31, 2015, Monsanto announced that it would contribute $3.6 million to the National Fish and Wildlife Foundation’s Monarch Butterfly Conservation Fund over the next three years. An additional $400,000 was included “to partner with and support the efforts of experts working to benefit monarch butterflies,” a companywide announcement read. An optimist may view this commitment as means to make amends – an attempt to right a wrong committed against butterflies. A cynic may see a carefully crafted public relations move that lacks long-term commitment to butterfly-friendly agricultural practice. Either way, Monsanto’s donation is a step in the right direction. Monarch butterflies can be saved, and individual citizens can absolutely aid these efforts. To raise awareness, reach out to government officials, herbicide companies, and farmers to let them know you care about the fate of butterflies. To actively aid conservation, plant local milkweed species on your property to provide nursery habitat for migrating monarch larvae. We are not powerless in the fight to save monarchs, and it is a battle worth fighting. They are an iconic American species: a source of inspiration for writers, artists, scientists, and children exploring their own natural world for the first time. Don’t let them down; don’t let monarchs fall.