PNAS found that the number of insects destroying plants has reached unprecedented levels

According to a new study led by scientists at the University of Wyoming, insects today are causing unprecedented damage to plants, even though their numbers are declining
.

The study is the first to compare the destruction of insect herbivores in modern plants to
the destruction of fossilized leaves from the late Cretaceous nearly 67 million years ago.
The results of the study were published in
the prestigious journal Proceedings of the National Academy of Sciences.

"Our work bridges the gap between people who study long-term plant-insect interactions with fossils and people who study such interactions in modern settings with fresh leaf material," said lead researcher Lauren Azevedo-Schmidt, a doctoral student at the University of Washington who is now a postdoctoral research associate
at the University of Maine.
"The difference between the modern and fossil records in terms of insect injury is striking
.
"

Azevedo-Schmidt conducted the study
with Alan Colano, a professor in the Department of Botany, Geology and Geophysics at the University of Washington, and Emily Menecke, an assistant professor at the University of California, Davis.

The study examined fossilized leaves with insect predation injuries from the Late Cretaceous to the Pleistocene period (more than 2 million years ago) and compared
them to leaves collected by Azevedo Schmidt from three modern forests.
This detailed study looked at the different types of damage caused by insects and found that all recent damages were significantly increased
compared to the fossil record.

"Our findings suggest that modern plants are experiencing unprecedented levels of
insect destruction, despite a general decline in insect populations," the scientists wrote.
Scientists believe that this difference can be explained
by human activity.

More research is needed to determine the exact cause of the increased damage from insects to plants, but scientists say warming climate, urbanization and the introduction of invasive species may be major contributing factors
.

"We hypothesize that humans have influenced the frequency and diversity of destruction in modern forests, with the greatest human influence following the Industrial Revolution
," the researchers wrote.
"Consistent with this hypothesis, herbarium specimens in the early 21st century were 23 percent more likely to be damaged by insects than specimens collected in the early 20th century, a pattern associated with
climate warming.
"

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

"This study shows that the intensity of human influence on plant-insect interactions is controlled not just by climate change, but by the way humans interact with the landscape
," the researchers concluded.