China will face yield losses in rice, wheat and corn -- the country's three main crops -- unless it takes steps to offset the effects of climate change, an expert warns.

"The impact of climate change, especially extreme weather and plant diseases and insects, will cause a bigger grain production fluctuation in China and bring more serious threats to the country's food supplies," said Tang Huajun, deputy dean of the Chinese Academy of Agricultural Sciences, China Daily newspaper reports

In an effort to safeguard China's grain security, the government last month said it would introduce legislation aimed at improving the country's grain production, protecting farmlands and to adopt policies favorable for the agricultural sector.

The government's Agriculture and Rural Affairs Committee is pressing for the legislation to include improvements to the national grain reserve system and measures to prevent foreign capital from undermining national grain security, state-run news agency Xinhua reports.

China, the world's second largest and fastest-growing economy, is the world's biggest grain producer.

Its grain output is expected to rise to more than 550 million tons after 2010's record production of 546.4 million tons, representing the eighth consecutive year for increased production, Ministry of Agriculture figures show.

China's need for grain continues to soar, with demand likely to reach 572.5 million tons by 2020. That's an increase of 47.5 million tons compared to 2010.

But if climate change continues, Tang warns, China's rice output could drop 4-14 percent in 2050. Wheat and corn output in 2050 could fall 2-20 percent and 1-23 percent, respectively. The three crops typically represent 80 percent of China's total grain production.

"China will be faced with a heavy task ensuring its food security, since negative effects of climate change has become more obvious and these are increasing," Qu Sixi, deputy director of the Ministry of Agriculture's department of international cooperation.

Just from flooding, 24.7 million acres of China's farmland was affected each year in the 2000s, compared with 12.3 million acres in the 1970s.

Meantime, China is increasingly searching outside its borders for reliable agricultural sources.

State-owned China National Cereals, Oils and Foodstuffs Corporation, the country's largest trader of grains and edible oils, plans to spend more than $10 billion on overseas mergers and acquisitions in the next five years.

"Because of the nation's limited agricultural resources, we have to look overseas," COFCO board member Jiang Hua said.