According to new research led by University of Wyoming scientists, insects are causing unprecedented levels of damage to plants today.
The study is the first of its kind, comparing insect herbivore damage to modern-era plants with that of fossilised leaves dating back to the Late Cretaceous period, nearly 67 million years ago. The research was published in the journal Proceedings of the National Academy of Sciences.
“Our work bridges the gap between those who study plant-insect interactions in deep time using fossils and those who study such interactions in a modern context using fresh leaf material,” says lead researcher Lauren Azevedo-Schmidt, a UW Ph.D. graduate who is now a postdoctoral research associate at the University of Maine. “There is a striking difference in insect damage between the modern era and the fossilised record.”
Azevedo-Schmidt collaborated on the study with UW Department of Botany and Department of Geology and Geophysics Professor Ellen Currano and University of California-Davis Assistant Professor Emily Meineke. The researchers compared fossilised leaves with insect feeding damage from the Late Cretaceous to the Pleistocene epochs, roughly 2 million years ago, to leaves collected by Azevedo-Schmidt from three modern forests. The detailed study examined various types of insect damage, discovering significant increases in all recent damage compared to the fossil record.
“Our findings show that, despite widespread insect declines, plants in the modern era are experiencing unprecedented levels of insect damage,” the scientists wrote, suggesting that the disparity can be explained by human activity.
More research is needed to pinpoint the precise causes of increased insect damage to plants, but scientists believe that a warming climate, urbanisation, and the introduction of invasive species have all played a role.
“We hypothesise that humans have influenced (insect) damage frequencies and diversities within modern forests,” the researchers wrote. “In line with this hypothesis, herbarium specimens from the early 2000s were 23% more likely to have insect damage than specimens from the early 1900s, a pattern that has been linked to climate warming.”
However, they argue that climate change does not fully explain the increase in insect damage.
“This research suggests that the strength of human influence on plant-insect interactions is controlled not only by climate change, but also by how humans interact with the terrestrial landscape,” the researchers concluded.