Billboards are a tool of advertising, conveying a brief message at high speed. To artist Stephen Glassman, they’re a canvas, and a potential tool for confronting pollution challenges as cities grow.

What better place to experiment than here in Los Angeles? This region supports an estimated two million cars every day, many of which pass by dozens of billboards. Summit Media, an LA-based company that owns billboards, offered Glassman and former advertising executive Dan Burrier a billboard in a highly trafficked part of LA to try out their  project. To understand how it’ll look, picture a simple billboard, but instead of an advertisement, imagine tall stalks of bamboo and other native plants that gobble up carbon dioxide and create a tiny,