The Encyclopedia of Earth is a wonderful reference from the Rachel Carson Center for Environment and Society. For example, it has an excellent section on Biodiversity and many other topics in life science. The Encyclopedia of Earth is affiliated with The Encyclopedia of Life, another excellent resource being developed.
Encyclopedia of Earth Exploration
Earth & Space Science, ESS2: Earth's Systems, ESS2.C: The Roles of Water in Earth’s Surface Processes, ESS2.D: Weather and Climate, ESS3: Earth and Human Activity, Life Science, LS4.D: Biodiversity and Humans