Mangroves in coastal Thailand are the main protection against deadly flooding from tsunamis, so it might seem wise to protect them at all costs. However, ripping out a few mangroves and replacing them with shrimp farms, an important local industry, doesn’t necessarily have to reduce the plants’ power to blunt tsunamis. And in that observation lies a fresh, quantitative approach to how policy makers can protect the environment and allow growth and development that improves local residents’ lives.