Gary Braasch, a pioneering photographer who traveled the world to document the increasingly rapid and far-reaching effects of global warming, died on Monday while taking pictures of the Great Barrier Reef in Australia, according to Reuters.

The reef, like many reefs throughout the world right now, is experiencing a coral bleaching event, which may be the longest-lasting such episode ever documented in modern times.

Reuters reported that Braasch, who was 70, was snorkeling with a companion at the Australian Museum’s Lizard Island Research Station. “He was documenting the effect of climate change on the reef,” the agency said.