But prehistoric life and ecology hummed along for millions of years in the Cretaceous before the asteroid showed up. Fossilized leaves show a record of insect predation not unlike what is seen on leaves today. On some leaves, the imprint of piercing and sucking insects is visible. Others show the ragged margins or holey centers of leaves chewed by hole feeding and margin feeding insects. Evidence of mining insects is also preserved, as are galls. The fossil record preserves even the totally skeletonized leaves that show only veins.
By looking at such damage, researchers can categorize the types of fossil insects that infested these forests 65 and 55 million years ago, and trace the extinction and evolution of species. Wilf and Labandeira of the Smithsonian looked at 13.5 thousand leaves across the K-T and identified 51 types of insect feeding damage. The researchers found that the K-T impact was associated with a significant and enduring loss of plant and insect species. Among insects, the most affected were the specialized feeders, those insects that fed on leaves of only one type of plant. Insects died both from the impact and because the trees that they fed on died. Specialized feeders were less able to adapt and eat off any tree available and so were more greatly effected. Only 21 percent of species made it across the K-T boundary, and only 11 species originate in the Paleocene indicating the recovery was not immediate. In fact, diverse vegetation does not return in the area studied until the warm early Eocene 12 million years after the impact.

Wilf sees lessons from the K-T that are critical for the 21st century as well. He notes that due to human activity, global change is occurring at breakneck speed today. Because of the geologically rapid pace of human-induced extinctions, habitat loss and climate changes, land plants currently face a situation more closely resembling the K-T than the P-E boundary. “The P-E transition was a relatively long, slow change that allowed the plants and insects to adapt to the shifting environment,” says Wilf. “At the K-T, species could not adapt in time because the change was so rapid. These rapid changes were much more like what we have today than the gradual ones that occurred at the P-E. Organisms cannot migrate in response to climate changes as they did during the Eocene because of because of freeways and parking lots, and the ongoing loss of habitat imposes severe and geologically sudden stress on ecosystems.”
Plants and insects that cannot migrate and have insufficent time to evolve have no other option but to go extinct.