Acid rain is caused by sulfur dioxide and nitrogen oxide emissions from the burning of fossil fuels. These gases react with water and oxygen in the atmosphere to form acids that fall to Earth as rain, snow, or fog. Acid rain damages trees, aquatic ecosystems, infrastructure, and can harm human health. It harms trees by dissolving minerals in soil and leaves, damages buildings by corroding stone and metals, and kills fish by lowering the pH of lakes and streams. While regulations and use of renewable energy can help address the problem, individual conservation efforts also make a difference in reducing the emissions that cause acid rain.