49 books • 9 series
Book #46: Rivera
Book #1: Atmosphere In Danger
Book #2: Oil Spills
Book #3: Ozone Hole
Book #1: The Seashore
Book #2: Sharks
Book #3: Volcanoes
Book #4: The Solar System
Book #1: Avalanches
Book #3: Earthquakes
Book #5: Famine and Drought
Book #8: Tidal Waves and Flooding