Plastic bags are essentially indestructible, yet they're used and thrown away with reckless abandon. Most end up in the ocean, where they pollute the water and harm marine life; the rest are burned in garbage piles, where they release harmful dioxins into the atmosphere. Melati and Isabel Wijsen are on a mission to stop plastic bags from suffocating their beautiful island home of Bali. Their efforts -- including petitions, beach cleanups, even a hunger strike -- paid off when they convinced their governor to commit to a plastic bag-free Bali by 2018. "Don't ever let anyone tell you that you're too young or you won't understand," Isabel says to other aspiring activists. "We're not telling you it's going to be easy. We're telling you it's going to be worth it."