Cicadas: Timing in the Age of Climate Change
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Chapter 1: The Enigmatic Cicadas
Cicadas, often referred to as America's favorite insects, are making their much-anticipated return. Brood X, a group of 17-year "magicicadas," is emerging across the Eastern United States. This event signifies the start of a cicada season that will see billions of these insects molting, calling out for mates, and ultimately leaving their remains scattered across yards and rooftops from New Jersey to Illinois.
This rare event occurs every two decades, serving as a poignant reminder of time's passage. “Periodical cicadas are the ‘bugs of history,’” notes Gene Kritsky, a biology professor at Mount St. Joseph University in Cincinnati. Kritsky, who blends entomology with history, has penned intriguing works like The Tears of Re: Beekeeping in Ancient Egypt.
The cicadas' predictable patterns are part of their allure. If a child was born during the last emergence of Brood X, they are now a teenager. Regardless of global events—be it a pandemic, conflict, or elections—these cicadas will reappear every 17 years, or every 13 for certain broods.
Chapter 2: The Impact of Climate Change
However, researchers are concerned that warming temperatures may disrupt these established timelines. Cicadas rely on internal biological clocks, spending the majority of their lives underground, where they absorb nutrients and count the years until they can emerge. In their 17th year, they begin to surface when the ground temperature reaches about 64 degrees Fahrenheit and has been softened by rain.
In recent decades, there has been a noticeable shift towards earlier emergence. Kritsky's analysis of historical records reveals that prior to 1950, cicadas typically began their emergence between May 20 and 28. Nowadays, they are appearing as early as the first few weeks of May. A preliminary study by Climate Central estimates that regions inhabited by Brood X are now 8 degrees Fahrenheit warmer than in 1970, and 1.1 degrees warmer than during their last emergence in 2004. This increase in temperature may lead to premature surfacing.
As temperatures rise, cicadas could also misinterpret their internal calendars. In 2017, Brood X cicadas were spotted emerging four years earlier than expected across the Eastern U.S. Other broods have also displayed similar patterns. “Broods II, III, V, X, XIII, XIV, and XIX have all spun out accelerated populations four years early,” Kritsky states, attributing this phenomenon to rising temperatures affecting over 20 states in the Eastern U.S.
The first video discusses how climate change could be affecting cicada emergence patterns, shedding light on the potential implications of warming temperatures.
Kritsky hypothesizes that cicadas may rely on the fluid in trees to gauge time. In unusually warm conditions, trees could begin to bud early, creating a "false spring" that misleads cicadas into thinking more time has elapsed than actually has.
Nevertheless, this theory remains speculative. John Cooley, a cicada researcher at the University of Connecticut, cautions that the increase in reported early cicada sightings could be a byproduct of heightened citizen engagement through apps like “Cicada Safari” rather than a genuine shift in emergence patterns.
The unique nature of cicadas, which only emerge every 13 to 17 years, complicates the collection of reliable data. “If you wanted a species to document climate change effects, periodical cicadas might not be your first choice,” asserts Louie Yang, an entomology professor at the University of California, Davis.
The second video explores the 2024 periodical cicada emergence, providing insights into their lifecycle and how climate factors into their timing.
Chapter 3: The Future of Cicadas and Climate Change
Despite the challenges of studying cicadas, they may offer valuable insights into our changing climate. The last emergence of Brood X in May 2004 occurred when atmospheric carbon dioxide levels were around 381 parts per million. Currently, those levels have risen to approximately 420 parts per million and continue to increase. When the offspring of this year's cicadas emerge in 2038, will they find a world transformed by wildfires, heatwaves, and rising sea levels? Or will they enter a landscape moving towards restoration?
“Seventeen years is a significant measure,” Yang observes. Humans often struggle to grasp large-scale or long-term changes, such as climate change. “We excel at understanding medium-sized objects and timeframes,” he explains. This makes cicadas, with their extended underground dormancy and sudden, vibrant emergence, a useful benchmark for assessing both the future and the past.
“In the span of two or three cicada generations, our lives—and the planet—are likely to change drastically,” Yang concludes. “It prompts us to reflect: Are we making the positive impact we hope for by the time the next cicada brood emerges?”