A man stands in shallow water near Yongxing Island, which was once home to coral reefs. [Photo provided to China Daily]

Huang Hui felt pleased that the illegal collection of corals in the South China Sea has declined as a result of stricter regulations.

But just a few years ago, she has witnessed what appeared to be fishing boats illegally stripping corals by scraping the ocean floor with trawl nets in the waters off an island in the Xisha chain.

Huang, a scientist with the South China Sea Institute of Oceanology at the Chinese Academy of Sciences, said she first saw the poachers in 2012.

They were harvesting corals that had been growing for five to eight years.

Poachers are a major problem because they not only harvest corals illegally, but do so in an aggressive and environmentally damaging manner, destroying the entire ecosystem of the seabed around coral reefs.

"So now we are trying to rejuvenate the underwater environment in the South China Sea by planting coral," Huang said.

"Growing coral is like growing a tree－it takes time, but has a tremendous effect on conservation."

Disappearing reefs

China's State Oceanic Administration says that since the 1970s climate change and human activity have resulted in the disappearance of 80 percent of coral reefs along China's coastline.

The reefs, considered the marine equivalent of tropical rainforests, have flourished for more than 500 million years, and although they cover just 2 percent of the ocean floor, they are home to 25 percent of all marine species.

Huang's research team has long studied the ecology of coral reefs, but since 2006 the increasing degeneration has led them to seek solutions.