BEIJING, Oct. 26 (Xinhua) -- An eight-year national marine survey wrapped up on Friday, giving authorities a clearer picture of China's coastal water resources.
Launched by the State Oceanic Administration in 2004, the government-funded survey indicated that China had a total of 19,057 km of continental coastline and 10,312 islands as of 2009, 569 of which are inhabited.
Nearly 90 percent of China's coastal cities are suffering from water shortages of differing levels, according to the survey. Of 52 surveyed coastal cities in 11 provinces, 28 have serious or extremely serious shortages of water, the survey said.
The survey, made possible by more than 30,000 maritime science and technology workers, revealed that pollution has appeared in more nearshore areas, despite a "generally sound" coastal environment.
The survey indicated that the total area of China's coastal wetland registered a decrease of 430,000 hectares during the 32 years following 1975, with the total coastal wetland area standing at 6.93 million hectares in 2007.
According to the survey, coastal wetlands shrank by some 57 percent compared with the total wetland area in the 1950s, while the coverage of mangrove and coral reefs decreased by 73 percent and 80 percent, respectively.
Coastal waters experienced an annual average of 83 red tides over the last two decades, mostly in the East China Sea, according to the survey.
Green tides have also been spotted in the Yellow Sea in recent years. Green tides that occurred in the summer of 2008 caused direct economic losses of 1.29 billion yuan (around 205 million U.S. dollars).
Red or green tides, which are believed to be caused by seawater pollution or overfishing, occur when algae accumulate rapidly in waters and discolor surface water.
The survey predicted an annual increase of at least 8 percent for the total production value of the marine economy. Its production value is expected to reach nine trillion yuan (1.43 trillion U.S. dollars) in 2020, or more than 10 percent of the country's GDP.
Entitled "Comprehensive Survey and Assessment of Coastal Waters," the project represents the largest marine survey conducted since the founding of the People's Republic of China in 1949.
According to the administration, the survey results will be used to map out a high-resolution remote sensing atlas for the country's islands and coasts, as well as provide data support for archiving the country's territorial sea base points and disputed islands.