What 13,000 Dead Grasshoppers Can Tell Us About Climate Change
Cesar Nufio is holding a box of dead grasshoppers. The insects, precisely pinned, with miniscule labels affixed beneath them, march down the box in neat, dark lines.
The grasshoppers are just a sampling of a 50-year-old set of 13,000 grasshoppers that Nufio, an entomologist at the University of Colorado, is using to learn about climate change. Until the scientist happened upon them about a decade ago, this collection was nearly forgotten – stored in 250 wooden boxes atop a shelf. Ever since finding the collection, Nufio has been piecing together the story of the lost grasshoppers, and is using them to understand how the change in the area's climate is affecting the insects.
"Each [box] just contained a random assortment, it seemed, of grasshoppers," said Nufio, an animated man with a shock of dark hair and intense eyes.
Then he discovered the notebooks. Gordon Alexander, the CU entomologist who made the collection, had left three detailed field books. They contained a wealth of data: grasshopper species at different sites going up in elevation, and the number of individuals of each species. They cataloged the life cycle of the grasshoppers over a set of three summers from 1958-1960.
"We know when they hatched, and when they went through the different stages and when they become adults," Nufio said.
The specimens themselves also contain information about body size and color, other traits that could be responding to climate change, said Nufio.
"I knew what I wanted to do in five years, ten years. I knew this was going to be a system that we could study climate change with," he said, recalling the moment when everything crystallized. "In a way, I feel that Alexander did the initial experiment that I needed to if I had a time machine."
Alexander's grasshoppers, combined with the notebooks cataloging weekly surveys at sites going up and down the mountains near Boulder, are like a snapshot of grasshopper life 50 years ago. For a researcher hoping to understand how warming is affecting species and ecosystems, that glimpse into the past is unusual and valuable, since it allows Nufio to compare that world to the present.
Lauren Buckley, a climate change ecologist at the University of Washington who has also worked with the grasshopper collection, called it "really special," in particular because of the detailed weekly field notes that accompany the grasshopper collection.
"The fact that he has a few years in the past as well as quite a few current years makes it more extensive than most of the data sets that we have to study responses to climate change," said Buckley.
Searching For Gordon Alexander
Before he could really understand Alexander's collection and data, Nufio needed to learn more about the man, who had died in a plane crash in 1973. He searched through the biology department's records and found next to nothing. He looked in the university archives and found Alexander's obituary. He searched for his children, to no avail.
"I had emailed anybody named Alexander who had touched a grasshopper," said Nufio.
Then one day, when chatting with a recently retired member of his department, Nufio mentioned Gordon Alexander. The faculty member, Peter Robinson, who remembered Alexander, told Nufio how to find his son Douglas, who lived in Chico, California.
When he reached Douglas Alexander, he was happy to help.
"Cesar called and said, 'by any chance are you Gordon Alexander's son,' and told me all of those collections had never been opened up."
Douglas Alexander, who had helped organize his father's collections when he died, had wanted the data, which he knew was valuable, to be saved and computerized.
"My wife and I were very excited, we drove back, and we told [Nufio] he should write a grant," he said.
The son also brought Nufio books from his father's collection, and other notes and papers.
As Nufio organized the old collection, he also decided to start his own survey, a modern version of Alexander's.
The Next 17,000
Grasshoppers jump, wings chattering, through fading wildflowers and tall grass on a site just below Sugarloaf Mountain, near Boulder. Cesar Nufio swooshes what looks like a giant canvas bag on a broom handle through a field.
After a few minutes, he opens up the bag – called a sweep net – showing the grasshoppers, brown and green, large and small, caught inside.
Normally, he would do this for an hour, counting every species and what stage of life they are in – grasshoppers go through six phases to become adults.
"I've been resurveying grasshoppers since 2006," said Nufio. Now, having documented over 180,000 grasshoppers in the field and pinned and labeled about 17,000 of them, he has a collection to match Alexander's.
So far, he's found a number of changes, some likely linked with long-term, local climate change. In the warmest years, grasshoppers have developed sooner – reaching adulthood as many as four to five weeks earlier than they did in Alexander's time. Species that like warmer weather have increased their numbers as well. He's also learned that parts of the mountains around Boulder – the middle altitude sites in particular – have warmed faster than the highest and lowest parts of the mountain, and that has meant grasshoppers in those locations have been more affected. He's also found that in alpine locations, while grasshoppers do well in warm years, the plants seem to be shorter and produce fewer flowers.
Climate isn't the only thing that has changed, though, said Nufio. At the field site where he caught the grasshoppers, he points out a green grass, thigh-high, that dominates the area. It's a non-native species, likely planted after a fire. Grasshoppers don't like it. Where it grows, there are fewer species than there were in Alexander's day.
Nufio had a hard time finding another old Alexander site. When he matched it up with old photographs, he learned that's because it has became Boulder's Fairview high school. Where prairie grasses once grew, school grounds and manicured fields now sit.
So far, Nufio hasn't yet found that grasshoppers are changing their size or color yet, one thing that scientists think may happen as the climate changes.
As climate continues to change, though, the bugs could be responding in new ways. What happens to grasshoppers could also indicate what is happening to bees, or butterflies, or other animals.
"In some ways, they're the voice of a lot of different organisms that are out there," said Nufio.
The CU scientist doesn't know how much longer he'll keep collecting grasshoppers; he'll soon run out of funding. He imagines his project being picked up again, maybe in another 50 years.
"They're going to go back and say,' oh my god, look at this collection,'" he said.