@clintflint - Corals won't go completely extinct because we can grow many of them in captivity, if nothing else. There are a lot of critically endangered animals at the moment who only exist in the wild because of captive breeding programs that have saved them. The kakapo in New Zealand is one example of this. They were down to fewer than 50 individuals at one point.
The giant panda is another example and I believe Przewalski’s horse is another one. It's not a perfect solution, but it's better than nothing.