Sewage and other waste is posing a serious threat to coral reefs worldwide. A study published recently in Ocean & Coastal Management found "90 percent of coastal protected areas in the Coral Triangle are affected by high levels of sewage pollution - up to 10 times highter than in nearby unprotected waters".

Collapse related because coral reefs support over 25% of all marine life despite accounting for far less than 1% of the ocean floor. When they're gone, they're gone. There are some small projects around the world that have restored a tiny bit of what is increasingly destroyed each year. They are unlikely to outpace the destruction, much less catch up with it.