Effects of Non-Point Source Pollution On Soil Degradation: Challenges and Opportunities.

Both point-source and non-point source pollution could lead to soil degradation and negatively affect ecosystem services from natural ecosystems and managed ecosystems. In China, point-source pollution from industrial development such as heavy metal and organic chemical contaminations poses imminent dangers to the environment and human health and need to be strongly regulated by environmental laws. In the US, non-point source pollution such as acid rain, elevated atmospheric nitrogen deposition, and elevated atmospheric CO₂ concentration are major threats to the long-term sustainability of soil resource and society. In the not-too-far future, such non-point source pollution will also become major issues in China and other developing countries. In addition, soil erosion due to poor agricultural practice leads to both ecological and economic losses at local, regional, and global scales. Non-point source pollution is often caused by “quantitative changes” of natural biogeochemical cycling due to anthropogenic activities. For example, reactive nitrogen input into earth biosphere from inert N₂ gas has more than doubled due to fertilizer manufacture and fossil fuel burning, leading to elevated atmospheric N deposition, acid rain, urban air pollution, N saturation in forests and grasslands, and eutrophication in freshwater and costal aquatic ecosystems. Scientific understandings of natural elemental cycling and its alterations in human-dominated earth landscape are urgently needed. Restoration of land resources, either by reforestation, or being linked to future biofuel crop plantation, could create new opportunities to address many non-point source pollutions, in addition to fulfill the goal of soil conservation. In my talk, I will draw examples from both US and China, focusing particularly on carbon and nitrogen cycling, and plant – soil feedbacks, to address broad-scale issues of non-point source pollution and soil degradation.