Characteristics of the Dynamic Changes of the Beidagang Wetland in Tianjin, China
北大港湿地动态变化特征研究

The Beidagang wetland is located in the southeast of Tianjin Municipality, possessing typical wetland characteristics and a variety of environmental and social service functions. It also has the richest biodiversity in Tianjin, even across the Bohai Bay area. The Beidagang wetland ecosystem has, nevertheless, been significantly degraded due to a range of human and natural factors, exhibiting progressively weakened wetland functions. Investigating the characteristics of dynamic changes of the Beidagang wetland is thus of great significance to ameliorate the quality of the wetland environment and to improve the overall ecosystem health in Tianjin. In this work, SPOT 5 satellite imageries (including both the panchromatic and multi-spectral bands) in September 2008 were acquired. In addition, a series of China-Brazil Earth Resources Satellite (CBERS) imageries were obtained for this study. Based on these imageries, information regarding water, vegetation, and land use of the Beidagang wetland over the period 2000-2008 was extracted with the aid of multi-spectral imagery classification algorithms and related image processing techniques. Samples of the land use for imagery classification and accuracy assessment were obtained from field investigations. Measures for protecting the wetland and promoting sustainable development were put forward based on analysis of its dynamic change characteristics. Results showed that 1) the water resources, vegetation, and land use of the Beidagang wetland experienced great changes from 2000 to 2008; 2) the scarcity of water supply was the major reason for water reduction. The wetland plant communities were progressively degrading due to the shortage of water resources compounded by salinization. There was a stable growth of the wetland vegetation observed from 2000 to 2002, followed by a continuing benign development of the growth over the next four years. However, the growth of the vegetation presented a marked degradation from 2006 to 2008, reaching the worst state in 2008 within the 9 year-period. The relationship between the change in the wetland system and changes in water resources was found to be closely related; 3) natural wetlands showed an artificialization trend involving increasing human impacts, suggesting that the artificial wetlands were incrementally occupied with the urban expansion. Continuing exploration of the wetland system has been inducing the degradation of the wetland environment. Establishing wetland water security mechanisms and achieving a virtuous cycle of integrating protection and utilization would be the effective ways to fundamentally protect and improve the environment of the Beidagang wetland.