From the research results , we can see that the initial reason , which leads to the degradation of xuanwu lake ecosystem , is pollution . pollution makes the water and sediments hypertrphiation , increases the opacity of water , and decreases the oxygen in water , so the wetland higher plant communities decrease or disappear . the wetland ecosystem loses the balance , while the biodiversity also decreases 研究结果表明，引起玄武湖湿地生态系统功能退化的初始原因是严重的环境污染问题，污染加剧了水体及沉积物中的营养盐含量，增加了水体的浑浊度，降低了水体中的氧含量，从而导致湿地高等植物群落减少乃至消失，尽而引起湿地生物多样性下降、生态系统失去平衡。
Meanwhile , the evaluation has changed from a single aspect su ch as vegetation and soil to a comprehensive evaluation including deterioration of environment and degradation of soil morphology and fertility . studies on a theoretical basis and basic principle for restoration and reconstructions . the study on benefits and functions of a restorated ecosystem 恢复与重建的生态系统功能与效益的研究，其效益评价由生物多样性、水土保持功能、土壤养分、小气候等单一方面转向利用灰色系统理论及系统工程方法进行综合评价。
