Nonpoint source pollution, environmental quality, and ecosystem health in China: introduction to the special section. 
The rapid economic and industrial growth of China, exemplified by a 10-fold increase in its gross domestic product in the past 15 years, has lifted millions of its citizens out of poverty but has simultaneously led to severe environmental problems.  The World Health Organization estimates that approximately 2.4 million deaths in China per year could be attributed to degraded environmental quality.  Much of China's soil, air, and water are polluted by xenobiotic contaminants, such as heavy metals and organic compounds.  In addition, soil quality is degraded by erosion, desertification, and nutrient runoff.  Air quality is further compromised by particulates, especially in heavily populated areas.  Research shows that 80% of urban rivers in China are significantly polluted, and poor water quality is a key contributor to poverty in rural China.  Economic and industrial growth has also greatly expanded the demand for water sources of appropriate quality; however, pollution has markedly diminished usable water resource quantity.  Desertification and diminishing water resources threaten future food security.  In recent years, China's government has increased efforts to reverse these trends and to improve ecosystem health.  The Web of Science database showed that the percentage of articles on China devoting to environmental sciences increased dramatically in recent years.  In addition, the top 25 institutes publishing the papers in environmental sciences were all in China.  This special issue includes seven articles focusing on nonpoint source pollution, environmental quality, and ecosystem health in China.  The major issues, and results of these studies, are discussed in this introduction.