Tianjin Coastal Wetland Ecosystem Degradation Index System And Evaluation

The coastal wetland is the special ecosystem which formed under the interaction between the sea and the land in the coastal zone scope,is one of the wetland ecosystem which most being abundant of bio-diversity,high of productive forces and valuable in the nature.It played an influential role in protecting the bio-diversity,storing water to defend the flood,purifying land source pollution entering the sea,complementing groundwater,regulating the weather aspects etc,simultaneously its natural resource was also the premise which causes the sea fishery,salt industry and salty chemical industry obtains the sustainable development。Under the interaction between sea and land,the coastal area of Tianjin grew wetland with abundant of resource and various types.However,under people's long-term and high-strength exploitation's influence,the area of natural wetland has a great deal of decrease,which is replaced by man-made wetland.The coastal wetland ecosystem receives the ellol'mous disturbance,is facing serious problem such as the natural wetland to wither,the ecological environment worsening.This paper took the most representative wetland as object of study which includes Qilihai ,Beidagang, Duliujian and Nandagang.It choosed five issue of topographic diagrams and the satellite remote sensing images from 1 975 to 2009,and revealed the temporal and spatial variation of Tianjin coastal wetland with applying RS and GIS technologies to the interpretation ,then analyzed the ecological environment present situation of Tianjin coastal wetland by gathering samples of wetland soil, water, plant and determination in the laboratory. On the basis of above, it constructed an ecosystem indicator system of Tianjin degeneratate coastal wetland according to the selection principle of evaluating indicator and the models of PSP(ressure-Station-Response).At the same time,a theoretic reference wetland was established by historial reference,methods of ecology and national environment standard. Using the mothod of AHP(Analytic Hierachy Process),the weights of indexs were calculated.Indexs were standardized by contrast value of actual indexs with theoretic reference wetland.The results of evaluation of degradation wetland ecosystem were calculation by the mothod of sythesis index.The main conclusions are as follows:(1) Before the 1980s, there was few man-made interference in Tianjin coastal wetland ,the wetland type is mostally natural wetland. After the 1980s, with the humanity developmental operation accelerating and intensifying, the wetland appearance characteristic obviously changed, namely the natural wetland area reduced, the artificial wetland area increased.The cultivation wetland, the salt field wetland, the rice paddy wetland area increased year by year, wetland environmental condition was worsening.(2) The Tianjin typical wetland soil has a high fertility, the nutritive elements content is in the normal level. the salt content is high, and there is no henvy metal pollution; The water environmental pollution is serious, and the COD content exceeds the allowed figure seriously,therefore,the water environment question is prominent. Halophytic vegetation is the major plant in Tianjin coastal wetland, and reed's coverage fraction is above 90%.(3) In the foundation of analysing massive evaluating indicator system of domestic and foreign wetland and according to the Tianjin coastal wetland's ecological environment characteristic, a set of ecosystem degeneration evaluating indicator system was constructed which was suitable for the Tianjin Binhai wetland. This indicator system unified the stationary index and the quota target fully, It both described the wetland,s ecology characteristic completely, and also carried on the determination or the graduation to its degree of degeneration, It may use in the majority of Binhai wetland ecosystem degeneration appraisal with making the adjustment slightly.(4) The evaluated results indicated that the degenerated index and the degree of degeneration of nseven Qilihai, Beidagang, Nandagang and Duliujian wetland were respectively as follows: 0.70 (mild degeneration), 0.68 (mild degeneration), 0.55 (moderate degeneration), 0.57 (moderate degeneration). The human factor was the predominant factor which caused the wetland degenerated, and the cultivation was the greatest influence to the wetland degenerated, next were water resources excess mining, water pollution and rainfall amount.(5) It proposed the countermeasures of resume and govern the typical coastal wetland. The measures consisted of the wetland restoring project, the perfect wetland management system and the legal framework and so on.