Coral reefs are home to many unique animals and plants that could not survive anywhere else. Tens of thousands of plant and animal species live in coral reef areas. Coral is very important ic controlling how much carbon dioxide is in the oceans. Without coral, the amount of carbon dioxide in the water would rise dramatically, which would affect all living things on Earth. Coral reefs also protect coastlines from strong currents and waves by slowing the water down before it reaches the shore. That's why they are called barrier reefs.
adapted from: On the job- Sea life scientist-Have you got what it takes to be a marine biologist? by Lisa Thompson