Butterflies Are Vanishing in the Western U.S. But Not for the Reasons Scientists Thought.

Olivia Cevasco

Mr. Ippolito

AP Biology - C Even

8 March 2021

Current Event 15

Elizabeth Pennisi. Mar. 4, 2021, et al. “Butterflies Are Vanishing in the Western U.S. But Not for the Reasons Scientists Thought.” Science, 4 Mar. 2021, www.sciencemag.org/news/2021/03/butterflies-are-vanishing-western-us-not-reasons-scientists-thought. 

Image Source: National Geographic Kids

“Earth is in the midst of an insect apocalypse, with thousands of species dwindling over the past several decades,” said Elizabeth Pennisi, a writer for Science. Until recently, scientists believed the decline in the insect population was chiefly due to the use of pesticides in farming; however, a recent study from Science suggests that insect populations, specifically the butterfly population, are also declining because of warmer fall weather due to global warming. Most notably, the monarch butterfly population has decreased 97.6%, from 1.2 million in 1997 to 29,000 in 2017, and Art Shapiro, an insect ecologist at UC Davis, noticed that butterfly populations are declining even in protected areas, such as the Sierra Nevada mountain range, prompting him to determine if this decrease is due to factors other than pesticides. Using databases, Shapiro et al tracked over 450 butterfly species from 70 locations in the US over a fifteen year period and was able to conclude that from 1997 to 2018, the overall butterfly population decreased 1.6% per year. Forister, an insect ecologist from the University of Nevada, who collaborated with Shapiro on the experiment, speculated that “The declines didn’t seem linked to human development or pesticide use—though such activities can still pose problems. Instead, the insects seemed to be disappearing in areas where fall temperatures had risen significantly more than summer temperatures over the past several decades, as in the U.S. Southwest. The warmer weather may disrupt the butterfly’s breeding cycle or negatively affect the plants they depend on.” He also noted that “some species may completely disappear from parts of their ranges in the coming decades.” 

This troubling conclusion is the result of decades of global warming from byproducts of our advancing world. Although the population of insects seems irrelevant to human life, a reduction in biodiversity of this scale can impact larger climates and even affect human health, since butterflies are pollinators. The loss of butterflies will surely affect the number of plants, which might exacerbate the effects of global warming without plants’ ability to remove CO2 from the atmosphere. And this population decrease isn’t just affecting butterflies; the number of bees and other insects are also on the decline because of rising temperatures. In order to maintain the planet’s biodiversity and health of its ecosystems, we must “take dramatic steps to curb global warming,” said Jessica Ware, an entomologist at the American Museum of Natural History. We need to start fixing the problems we’ve created so entire insect populations don't go extinct and cause massive problems. 

This article provided an overview of the study, had a strong message that we need to step up to solve this problem, and discussed the process and results of the study; however, it didn’t provide much statistical data to support the conclusion. For instance, it talked about rising temperatures, but didn’t put a number on the increase. It also said that the population was declining from both pesticides and temperatures but didn’t compare the percentage of decline due to pesticides and the percentage due to temperature. To a reader trying to believe the findings, a lack of data removes credibility. I had to find extra information about the decline in monarch population, as that wasn’t provided in the main article. Pennisi’s article did a good job incorporating quotes from the lead scientists and other experts on this issue, but the lack of supporting data could be improved to bolster her argument.