China's sharp rise in sulphur dioxide emissions, the main component of acid rain, is ruining the nation's croplands and threatening the food chain in rivers and lakes, experts said Sunday.

The emissions, largely caused by burning coal to sate China's booming appetite for electricity and by vehicle exhaust, are further exacerbating severe ecological degradation in the world's most populous nation, they said.

China announced this week that it emitted nearly 26 million tons of sulphur dioxide last year, a 27 percent increase since 2000, making the nation the world's biggest polluter of acid rain-causing substances. "The sulphur dioxide acidifies the soil, hurting the roots of the crops that farmers are growing and reducing total yields," Edwin Lau, assistant director of the Hong Kong branch of Friends of the Earth, told AFP.

"Acidity of rivers and lakes also affects the growth of marine organisms, killing the lower-level species needed by bigger organisms to survive and disrupting the food chain." Such negative impacts on the environment could lead to social instability in acid rain-hit areas as Chinese crop growers and fish farmers increasingly struggle to earn a living in face of a worsening environment, Lau said.

Each ton of sulphur dioxide causes 20,000 yuan (2,500 dollars) in economic losses, according to Li Xinmin, deputy director general of the State Environmental Protection Administration's pollution control department. This means China suffered nearly 65 billion dollars in economic losses last year from sulphur dioxide emissions, he told journalists on Thursday. Over half of the 696 cities and counties under a national monitoring program experienced acid rain last year due to sulphur dioxide pollution, the administration said in a report.

"The effects of acid rain on China is going to be much worse than in the United States and Europe when they had acid rain problems in the 1970s," Paul Harris, a China expert monitoring the nation's environment from Lingnan University in Hong Kong told AFP.

"China's soils are already in bad shape after being depleted following centuries of farming. Soil scientists will tell you that things are already on the edge in China."