The report, published Tuesday in the Journal of Animal Ecology, finds that some beetles in British Columbia, Canada, are shrinking as their habitats heat up.
“In nature, there is so much going on that can affect body size so we weren’t sure we were going to see anything,” said lead author Michelle Tseng, an assistant professor of botany and zoology at the University of British Columbia. “This research provides evidence that climate change is affecting even the smallest organisms out there.”
Scientists expect organisms to respond to climate change by changing the timing of their life stages, moving to new regions or shrinking.
The findings present some of the first evidence outside of a lab – where the environment and living conditions can be controlled – that global warming is already affecting the size of at least some organisms.
Tseng asked some of her students to determine whether this phenomenon is occurring by examining historical weather data and beetle specimens at UBC’s Beaty Biodiversity Museum.
Assisted by curators at the museum, the students reviewed eight species of beetles from two regions in British Columbia – the Lower Mainland and Okanagan. The team photographed more than 6,500 beetles and inputted data on each of the insects, such as where it was found and when it was collected, into a database.
“We got data from 100 years of caught specimens,” said co-author Sina Soleimani, one of Tseng’s students, who is now pursuing a doctorate in pharmacy at UBC. “It’s cool that people have been collecting these insects since 1910 and noting all of their collection information. That’s probably what makes our paper stand out.”
The students measured the beetles to determine whether they had changed in size over the past 40 or 100 years and used a climate database to collect data about environmental changes in the two regions where the beetles lived. They found that autumn temperatures have increased by about 4 degrees Fahrenheit in Okanagan and nearly 3 degrees Fahrenheit in the Lower Mainland over the past 45 years.
At first, the data did not appear to signify a clear trend as some beetles were shrinking while others were not. On closer examination, however, the students found that the larger beetles shrank, while the smaller ones remained about the same size.
The four largest beetles species shrank 20 percent over the past 45 years.
“When these organisms were collected, I don’t think anyone ever thought that they were collecting them so we could monitor how they are changing,” Tseng said. “Museum collections contain more biodiversity now than will ever be collected again.
“It’s incredible that the diversity of collections in museums can help us understand and predict how organisms might change in the future.”
Though the project began as a class assignment, the students spent a lot of extra time assembling all the data into a research paper. Nine students kept working on the project well after the class ended and they graduated from UBC.
“This is my first paper that I’m publishing and it’s 1 1/2 years after the class ended,” said co-author Katrina Kaur, a former UBC student who is now completing a master’s degree at the University of Toronto.
“It was a valuable experience as an undergraduate student. It was tough but I’m glad I stayed involved and saw it through.”