STORY: What was once a sea of colorful reefs off northern Bali has now turned ghostly white.

For the past 16 years, Indonesian conservationist Nyoman Sugiarto has been working to preserve coral reefs near his village Bondalem.

But his work was undone by recent mass coral bleachings,

which he blames on warmer sea temperatures triggered by climate change.

:: Nyoman Sugiarto, Conservationist

"The coral was almost 90% bleached at that time. No matter which type of coral, whether it was branching or it was massive, they were all white. So we were shocked and of course, it also negatively affected the coral we planted. It's not just the natural ones, but it's the ones we planted that make us miserable. It hurts, a lot of coral that we planted died."

Coral bleaching occurs when coral expels the colorful algae living in its tissues.

Without the algae the coral becomes pale and vulnerable to disease or death.

In April, the U.S. National Oceanic and Atmospheric Administration said more than 50% of coral reefs in the oceans are experiencing bleaching-level heat stress.

It's the fourth global bleaching event in the last three decades.

Indonesia accounts for 18 percent of the world's total coral reefs. That's according to the country's tourism ministry.

Coral bleaching in Bali in 2023 was mainly caused by rising sea temperatures caused by the El Nino phenomenon.

Even though Indonesia's corals are more resilient and tend to recover faster,

marine expert Marthen Welly says it won't be enough to withstand climate change.

:: Marthen Welly, Marine conservation advisor, Coral Triangle Center

"The process of coral bleaching or global warming is bound to occur more often than usual in Indonesia, the previous periods have beenin 1998, 2010 and 2016, but now the interval between bleaching events is getting shorter. It's predicted coral bleaching will occur quite often in the future in Indonesia or the Indo-Pacific, between the next one or two years with the current temperature."

But Sugiarto is determined to continue his campaign to conserve corals

and is advocating the mission to younger Indonesians.

"We hope more people become aware and join the action with us. Also, we hope that we can recover all the coral that used to exist in Bondalem as according to our elders, coral reefs here were very beautiful."