If the ocean is our planet’s “cradle of life”, then—in terms of their role in maintaining biodiversity—coral reefs are the ocean’s "tropical rainforests". Making positive contributions to marine ecological protection, Hainan is home to a group of people who have been quietly working to protect this so-called “underwater rainforest". In honor of the 17th World Oceans Day and 18th National Ocean Publicity Day, we would like to approach these people and hear from them some of their stories about reef conservation work.

Friday night at the South China Sea Tropical Ocean Research Institute in Sanya Bay, and the tide is going out. As the water recedes a wide variety of corals emerge from beneath the waves. They are the healthy start of a new reef that Director Chen Hong and his team have been working on for many years.

Director Chen Hong (right) and his assistant fixing live corals on a coral nursery rack.

Director Chen Hong (right) and his assistant prepping a drone to deliver populated coral nursery racks to their target sea area.

On May 30, scientific researchers used a remote control drone to deliver populated coral nursery racks to their target sea area. 

After Director Chen and his assistant fixed live coral seedlings on a coral nursery rack, they used a remote-control drone to slowly lift the rack and accurately deliver it to their target sea area.

As one of the south Chinese island province’s pioneers in coral cultivation, the almost 60-year-old Chen Hong has been engaged in rewilding of the ocean floor for over 30 years. He dreams of a day when the waters around Hainan Island are once again filled with a colorful "underwater rainforest". Never once considering the possibility of giving up, he has spent hundreds if not thousands of hours risking life and limb to plant new corals.

Carrying out regularly scheduled “forest protection” work, divers at Wuzhizhou and Fenjiezhou islands are part-time guardians of the reef. Fenjiezhou Island “park ranger” observing coral growth on May 24, 2017.

As one of the planet’s most biodiverse ecosystems, coral reefs are often referred to as the ocean’s "tropical rainforests". Worldwide, they play a vital role in maintaining biodiversity, stabilizing coastlines, and promoting the carbon cycle. In China, they also help support the nation's strategic goals of reaching carbon peak by 2030 and being carbon neutral by 2060, and defending maritime-related rights and interests. However, the affects of climate change, as well as pests, disease, and human activities mean that coral reefs worldwide are continuing to die. As home to the majority of China’s coral reefs, Hainan has—in recent years—been steadfastly working in the scientific protection and restoration of coral reefs and continuously improved the diversity, stability and sustainability of the local marine ecosystem.

Three underwater “park rangers” at Fenjiezhou Island cleaning up seabed garbage and transplanting coral fragments on May 25, 2017.

Healthy coral reefs not only provide food and shelter for marine life, their efficiency at carbon sequestration means that they play a vital role in global climate regulation. Taken on May 1, 2017, the picture shows a restored coral reef where fish gather, live, and reproduce.

Nowadays, Director Chen has cast off his identity as a lone wolf, fighting a battle with teeth and claws and a heart of stone. Instead he is part of a huge army of scientific research teams and environmental protection forces working together to protect Hainan’s “underwater rainforest”.

On June 3, in a lab at Hainan University, coral reef ecology expert Li Xiubao's research team is devoting themselves to finding innovative paths for reef restoration. Over the past few years, the team members’ regular visits to Hainan’s vast sea areas from the waters around the big island out to the Nansha and Xisha archipelagos have revealed rapid development in coral protection and restoration.

Because of their work, these special "park rangers" have many opportunities throughout the year to visit the colorful world beneath the waves.Carrying out regularly scheduled “forest protection” work, divers at Wuzhizhou and Fenjiezhou islands are part-time guardians of the reef.

Director Chen Hong (left) and his assistant taking seawater samples at finger coral (Montipora digitata) colonies. A new coral reef ecosystem has already started to grow here. 

Unfortunately, the affects of climate change, as well as pests, disease, and human activities mean that coral reefs worldwide are continuing to die.Taken on July 4, 2024, the picture shows Chen Hong transplanting coral seedlings onto a dead stony coral. These artificial plantings will help bring the coral “back to life. ” 

A given reef’s degree of biodiversity is a good representative of that reef’s overall health.Taken on July 4, 2024, the picture shows researchers checking reefs’ biodiversity level by collecting samples of companion species.

The use of technological forces such as unmanned aerial vehicles and underwater robots in coral reef protection and restoration is injecting new vitality into the work which researchers are doing.

Wang Aimin (Hainan University Professor, and Hainan International Blue Carbon Research Center Chief Scientist) and his team use underwater robots to monitor the health of corals; and plans are already underway to use satellite remote sensing to track the area and health of coral reefs over large areas.

Taken on June 3, 2025, the picture shows coral bleaching researchers at the Hainan University Coral Reef Restoration Lab.

Taken on June 3, 2025, the picture shows researchers at the Hainan University Coral Reef Restoration Lab sorting bleached and healthy coral samples as part of preliminary processing for microscope observation experiments.

After the tide has receded, a large patch of coral is revealed growing in Sanya Bay.Taken on July 4, 2024, the picture shows researchers walking carefully between the reefs as they observe coral growth.

Over the years, Hainan has put great importance on constructing itself as an “ecological province. ” As a result of the island province putting coral reef protection and restoration in a prominent position, a variety of measures have been promulgated to make Hainan's reefs a landmark project in its construction as national ecological civilization pilot zone. Growing awareness by the common man of marine environmental protection means that more and more people are willing to contribute their efforts to the rewilding of the ocean floor. The combination of their mental and physical labor is a guarantee for the building of a solid ecological foundation for the sustainable future of China’s "blue homeland”.