HAIKOU -- In a field in Dongzhaigang National Nature Reserve, South China's Hainan province, Wang Shijun stepped on the mud to carefully observe the seedlings of red-flowered black mangroves.

"This red-flowered black mangrove tree is the third generation," said Wang, 67. "Look at the flowers -- they are so beautiful!"

A national first-class protected wild plant in China, the red-flowered black mangroves are known as "coast guards." Due to a lack of protection, their wild population in China decreased from 350 in 2006 to 14 in 2014.

In recent years, with the efforts of people like Wang Shijun, the number of mangroves has increased to about 2,300, an epitome of the growing local efforts to protect the ecological environment.

Wang is a retired employee of the Hainan Dongzhaigang National Nature Reserve Authority. In 1980, Wang went to work there. In the following year, he participated in an investigation of mangrove distribution in Hainan and got to know the red-flowered black mangroves in Dadun village, Lingshui Li autonomous county.

"At that time, there were four or five hundred red-flowered black mangrove trees, which were spectacular at first glance," Wang recalled.

In 2013, the number of trees dropped sharply and even reached the verge of extinction.

Wang was devastated.

So he volunteered and started conservation work on the trees with several young colleagues in August of that year.

"At that time, the seeds were virtually lost. Later, we found some 100 seeds in the cracks in the trunk of a tree," Wang said.

Because the seeds were too precious, Wang chose to cultivate them on his home balcony. In order to simulate the survival environment of the seeds, he also brought back soil and water from Sanya in southern Hainan.

"At that time, 16 seedlings were cultivated, but they mostly died because they did not adapt to the balcony environment," Wang said. "Only one seedling survived."

In 2014, Wang and his colleagues went to Sanya again to search for seeds of red-flowered black mangroves. This time, they put what they found in a nature reserve for cultivation.

"We managed to cultivate 240 seedlings and were very excited," Wang said.

However, something unexpected happened. A strong typhoon landed and almost wiped out these seedlings.

"The sludge brought by the seawater after the high tide buried all the seedlings. These seedlings were each less than one centimeter tall," Wang said. "Later, we used cotton balls to brush them one by one, and it took about half a month to save them."

"Red-flowered black mangrove seedlings are very delicate. Crabs and mice are their natural enemies," Wang said. "Crabs will claw out after high tide. If they are not driven away by night, they might eat up all the seedlings the next day."

It is necessary to water the trees four or five times a day. Otherwise, they will suffer from sunburn. After half a year, when they grow up, crabs will no longer pose a threat, Wang said.

About eight years ago, the Dongzhaigang National Nature Reserve Authority vacated a base of 1.33 hectares for the mangrove plantation.

"The trees transplanted here grow very well, and the biggest one is three or four meters high," Wang said.

Wang said he hopes that the red-flowered black mangroves will be out of danger soon.

"It is the most meaningful thing I have ever done to have saved these mangroves for the country," he said.