Ecologist Zhao Lianshi has spent the last few years photographing the threats facing China’s declining mangrove forests
Flocks of herons rest in mangrove forests at Beihai, Guangxi.
Shells attached to a mangrove tree rooted on a beach. When the tide recedes, sealife is left behind.
Polluted water in a mangrove forest in Beihai, Guangxi. Research by Xiamen University has found that mangrove forests can absorb nutrients such as nitrates and phosphates, as well as heavy metals such as mercury, cadmium, lead, copper and zinc. In the future mangrove forests and other coastal plants could be used as a natural way to clean up industrial and domestic waste water.
There are limits to what the mangrove forests can handle. Pollutants that the mangrove forests cannot absorb flow into shallow coastal waters and lead to increased plankton numbers, jellyfish and algal blooms, often killing off large numbers of shrimp and fish.
The dumping of waste water also poisons fish. In this picture dead fish lie on the beach near a waste outlet. Sewage outlets are close to the beach and increased tourist numbers are putting more pressure on the environment. Young fish stick to shallow inshore waters, and are the main victims of urban sewage outlets.
A sewage outlet
Rubbish is also a threat – this picture shows a dried up mangrove forest strewn with rubbish. Earlier this year, 500-year-old white mangrove trees died in large numbers in Zhenjiang, Guangdong. Liu Yi, secretary-general of the China Mangrove Conservation Network, blamed the deaths on rubbish.
Construction and aquaculture have destroyed much coastal vegetation. Aquaculture is giving way to more profitable property and tourism development, and sea reclamation is turning carbon sinks into new carbon sources. The picture shows where vegetation has been dug out to allow construction.
The lack of vegetation results in severe coastal erosion. Studies on the Yellow Sea and the Gulf of Bohai have found that in the most severe cases 230 metres of land can be lost in a single year.
In some places local vegetation has been dug out to be replaced with more aesthetically pleasing trees. This is costly and results in desolate beaches. These trees were planted on the beach, but were quickly killed off by the salt.
Without mangrove forests and vegetation to absorb it, urban sewage covers the beach, damaging the ecosystem and giving off a foul smell. Populations of snails, shellfish, crabs, anemones and molluscs plummet, and bird feeding grounds and habitat are lost. Only algae flourishes.
China’s mangrove forests have shrunk from an area of 42,000 hectares 40 years ago, to only 14,600 hectares today, due mainly to excessive land reclamation for development and clearing for aquaculture.
Mangrove forests are rich in dead leaves and other forms of humus and a habitat for many inshore animals. They are also known as the nursery of the seas – 75% of tropical fish species spawn here. Growing in inter-tidal zones, they absorb the power of typhoons and the tides, preventing coastal erosion and protect coastal ecologies.
After a number of years of decline, mangrove forests today only remain in the provinces of Guangxi, Guangdong, Hainan, Fujian, the south of Zhejiang and Taiwan. Those in Guangxi are largest, accounting for 31% of all China’s mangrove forests.
Ecologist Zhao Lianshi has been studying mangrove forests – the “guardians of the coast” – for the last few years, using his camera to document the crisis mangrove forests face.