But after a lifetime trying to make sense of the vast ecosystems that lie beneath the ocean’s surface, the 73-year-old is now becoming a prophet of their extinction.
“It’s the beginning of a planetary catastrophe,” he tells CNN. “I was too slow to become vocal about it.”
In 2016 and 2017, marine heat waves caused by climate change resulted in mass bleaching, which killed about half of the corals on the Great Barrier Reef, along with many others around the world.
“Somewhere between a quarter and a third of all marine species everywhere has some part of their life cycle in coral reefs,” he says. “So, you take out coral reefs and a third to a quarter of all species gets wiped out. Now that is ecological chaos, it is ecological collapse.”