But scientists are having a hard time illustrating these problems as shifting baselines continue to redefine what is considered normal for reef health.
Australian scientists now report that coral cover on the Great Barrier Reef has fallen sharply in all three sections of the reef for the first time in 35 years of continuous monitoring.
Heat-tolerant genes may spread through coral populations fast enough to give the marine creatures a tool to survive another 100 years of warming in our oceans.
Thirty percent of the coral system was wiped out by warming waters in 2016; another 20 percent died off this year.
Such predictions could help fisheries prepare for the future.