One of the most important tropical habitats for young fish is mangrove swamps.
In the last 40 years, 80% of China's mangroves have been destroyed.
But at the Dongzhaigang Mangrove Reserve in Hainan,
a remarkable conservation initiative is bringing young Chinese volunteers together
to plant mangrove saplings in the glutinous mud.
For many of these city-born students,
such unglamorous work demonstrates their commitment to their country's environment.
Like other heavily populated countries,
China today is faced with a challenge.
How best to protect nature in an increasingly crowded space?