Research finds unprecedented amounts of insects damaging plants

Today, insects are causing unprecedented damage to plants even as insect numbers are declining, according to a new study led by University of Wyoming scientists.

The first study of its kind compares damage from insect damage to modern plants to that of fossilized leaves from the Late Cretaceous nearly 67 million years ago. The results appear in the journal Proceedings of the National Academy of Sciences.

“Our work bridges the gap between those who use fossils to study plant-insect interactions over long periods of time and those who study such interactions in a modern context using fresh leaf material,” says lead researcher, UW Ph. D Graduate Lauren Azevedo-Schmidt, now a postdoctoral fellow at the University of Maine. “The difference in insect damage between modern times and the fossil record is striking.”

Azevedo-Schmidt conducted the research alongside Professor Ellen Currano from the UW Department of Botany and Department of Geology and Geophysics and Assistant Professor Emily Meineke from the University of California-Davis.

The study examined fossilized leaves with insect damage from the Late Cretaceous to the Pleistocene, just over 2 million years ago, and compared them to leaves collected by Azevedo-Schmidt from three modern forests. The detailed investigation examined different types of damage caused by insects and found significant increases in all recent damage compared to the fossil record.

“Our results show that plants are experiencing unprecedented levels of insect damage in modern times, despite widespread insect declines,” wrote the scientists, who suggest the disparity may be explained by human activities.

More research is needed to determine the exact causes of increased insect damage to plants, but scientists say a warming climate, urbanization and the introduction of invasive species likely had a major impact.

“We hypothesize that humans have influenced the frequency and variety of (insect) damage in modern forests, with the greatest human impacts occurring after the industrial revolution,” the researchers wrote. “Consistent with this hypothesis, herbarium specimens from the early 2000s were 23 percent more likely to have insect damage than specimens collected in the early 1900s, a pattern that has been linked to global warming.”

But climate change doesn’t fully explain the increase in insect damage, they say.

“This research suggests that the magnitude of human influence on plant-insect interactions is not driven solely by climate change, but rather by the way humans interact with the land landscape,” the researchers concluded.