Jan. 21 - China is facing daunting challenges to address environment pollution and ecosystem degradation with its remarkable economic growth, and its future for a sustainable economic development relies on efficiency improvement, said a United Nations Environmental Programme official."The future for a sustainable economic development, I believe, relies on cooperation across the world in industrial restructuring, efficiency improvement, adoption of renewable energies, and adjustment of the current modes of production and consumption," said UNEP deputy executive director Shafqat Kakakhel in his letter to a recent economic forum held in Tianjin.China has become a large economy in terms of nominal gross domestic product, thus China's impact on global growth, resource allocation, trade and investment has direct consequences for the entire world, Kakakhel said in the letter.In efforts to protect environment and build an energy-saving society, the Chinese government will accelerate the establishment of a standard scientific evaluation system on energy consumption to meet energy and pollution targets, according to Xie Fuzhan, head of the National Bureau of Statistics."China is playing an increasingly important role in the international development arena, and taking on more and more responsibilities in global environment governance and sustainable development," said Kakakhel.