Basically, air pollution makes an absolute mess of plant communication. And it’s only getting worse. The cascade effects are daunting. Plant defense mechanisms—like the ability to turn bitter when warned of an oncoming insect attack, for example—are often the main way those pests are kept at manageable levels. This sort of natural pest control doesn’t work as well if plants can’t pass messages. “Some species of pests that are normally controlled might reach outbreak level,” Holopainen said.
