基于投影寻踪的城市生态系统健康评价

Health assessment of urban ecosystem based on a projection pursuit model

掌握城市生态系统的健康水平,对城市实施可持续发展具有重要意义。采用一种新型的多指标数据处理方法-投影寻踪模型,选取典型指标,利用基于实数编码遗传算法优化求取最佳投影方向,对广州市2000年、2005年的城市生态系统健康状况进行评价。评价结果表明:2000年,广州市对应的等级值为2.95,处于亚健康状态,符合其客观状况,该结果与采用模糊综合评价法所得结论一致;2005年,广州市对应的等级值为3.48,仍处于亚健康状态,但其等级值大于2000年的数值,等级值在增大,表明经过5a的建设,广州市的生态系统健康状况在不断好转。此外,与模糊综合评价法相比,该模型能精确地刻画出生态系统的具体健康水平,具有较高的评价精度和区分度。

Assessments and understanding of urban ecosystem health status are of great importance to the sustainable urban development. A health assessment of urban ecosystem was conducted in Guangzhou City in 2000 and 2005 by using a novel multi-indicator data processing method, projection pursuit model, in which the optimal projection direction was obtained based on real-rode genetic algorithm. Results predicted that the grade value of Guangzhou City in 2000 was in a sub-health status, which was in agreement with the real world data. In addition, output from the model is consistent with that obtained from the fuzzy assessment method. The grade value of Guangzhou City in 2005 was also determined as ＂sub-healthy＂ based on the actual monitoring data; whereas the model grade value for 2005 was larger than that for 2000. The increased value indicates a continuous improvement of ecosystem health in Guangzhou city during the past five years of efforts. Compared with the fuzzy assessment method, the model was able to accurately assess and project the health status of an ecosystem with higher precision.