Beijing has invested billions in the oil-rich country and may now have to step up to ensure stability prevails...As the world anxiously watches the southern Sudanese vote on whether to secede, one country has more to lose than most if civil war returns to Sudan. With an estimated 24,000 of its citizens living there and billions of dollars worth of investments in the country, China is the key foreign player...China National Petroleum Corporation (CNPC)...now has controlling stakes in the biggest energy consortiums operating in Sudan...[T]here is a possibility that Khartoum could close the pipeline should the south vote for independence. This decision would not only be devastating for the underdeveloped and oil revenue-dependent south, but would also disrupt China's oil supply. To counter this and to secure access to the south's resources after secession, China has started to build closer ties with the south... But many southerners have complained about the refineries that have been built on their land and the resulting environmental problems, like water contamination and sprawling lakes of toxic waste, and say that they have seen little of the wealth generated by oil production.