If you are unfamiliar with a topic, it is often best to start with an encyclopedia, or reference book to gain a basic understaning of your topic as well as terminology used in the field.
Some are online, others not. A few titles to browse. Remember, you can learn a lot from a book by just using one chapter!
[Note: The link connects to the full record in OneSearch]
Habitats and ecosystems : an encyclopedia of endangered America