Emerald Ash Borer Agrilus planipennis

Here's an invasive species success story—and not the good kind. Native to northeastern Asia, the emerald ash borer is a glittering green jewel beetle that's been catastrophic for ash forests in North America and Europe. Females lay eggs in bark crevices, and larvae tunnel underneath the bark, devastating entire trees from the inside out. A single borer can kill an ash tree within one to two years, which is why it's sparked massive coordinated efforts to contain its spread through monitoring and biological control.

In its native range, it remains harmless at low densities—a reminder that location matters when it comes to ecological balance.