Environmental experts are calling on authorities to control land reclamation, chemicals in waters and fishing on Chinese seas, as they warned that human activity has "severely degraded" the country's marine ecosystem.

About 147,000 square kilometers of Chinese seas were contaminated, as of 2009, and major inlets and estuaries, including the Liaodong Bay, Bohai Bay, Laizhou Bay, Jiaozhou Bay and the mouth of the Pearl River, were seriously polluted, according to a report released on Thursday by a research group of the China Council for International Cooperation on Environment and Development (CCICED).

The research group, composed of experts from China, Germany, the United States and the Netherlands, pointed out in the report that coastal wetlands were lost and biodiversity decreased as a result of pollution, land reclamation, and the invasion of alien species.

Meanwhile, China's aquatic ecosystem was deteriorating despite government endeavor to improve water quality and restore water protection projects, the report said.

Aside from climate change, excessive consumption of water resources and discharge of water pollutants, as well as the over-exploitation of water resources, have accelerated the degradation of the country' s aquatic ecosystem, it said.

Further, the report noted that some areas were challenged by heavy soil pollution and degradation of forest, grasslands and wetlands.

CCICED is a high level, non-profit international advisory body established upon the approval of the Chinese government in 1992.

The chief tasks of CCICED include exchanging and disseminating international successful experiences in the field of environment and development, studying key environmental and developmental issues in China, and putting forward policy recommendations to Chinese policy makers.