The Environmental Change And Degradation Of Modern Yellow River Delta Coastal Wetland

Coastal wetland is an important type of wetland, one of the highest productivity of ecosystem on the earth. Due to its remarkable primordial, vulnerability and scarcity, the Modern Yellow River Delta coastal wetlands (MYRDCW), as a place for birds to inhabit, reproduce and migrate, plays a very important role internationally. In recent years, it has attracted many domestic and international researchers to study it. The achievements have been fruitful. But there are few studies on its environmental evolvement and degradation. Supported by findings from field surveys and other means, the research in this paper studies the environmental change and degradation, and evaluates its degradation as well for MYRDCW.MYRDCW has evolved and developed on the lobe of deposit body. It has close relationship with water and sand in Yellow River (YR). From 1976 to 1996, during the period when YR flowed along Qingshuigou, the development of new lobe has undergone four phases: outspread on the plane shaped like a sector, expansion on lengthwise orientation, enlargement on widthwise orientation and alteration after abandoned. Because of the decrease of the amount of sand sources in YR since it changed its course at Qing 8 in 1996, the new spit of the river mouth started to have the characteristic of frequent alternated between erode and silt. Impacted by human activities, the development of coastal wetland has shown new characteristics. The disturbance from sources including mankind and the nature are external conditions for it to develop and evolve continuously.With the extension or erosion of new land, the vegetation develops and carries out straightforward or converse succession on the newborn wetlands. But overall it has the characteristic of apparent saline characteristics. Reed is the predominant community on the newborn coastal wetlands. As the coastal wetland is silted higher and the outfall extending, the biomass in the ecosystem mainly consisting of herbaceous plant community gradually decreases going upstream along the river.Experimental data indicates that silt is the predominant component in MYRDCW. The environmental chemical characteristics differentiate each other remarkably among different regions such as the current outfall area, abandoned outfall area and oil field area. Under the different habitats of reed, iodine weed, chionese tamarisk and beach land, all factors what have tested also show apparent differences. The analysis of the relationship among the chemical elements indicates the chosen 22 elements have the characteristic of very good co-existing combination in MYRDCW. The amount of organics and the salinity have a positive correlation. This reflects the area's saline environment. The amount of organics and granularity has a negative correlation, which indicates the composition of particles size affects the enrichment of organics.Based on interpretation of remote sensing (RS) images and its classification, methodology of landscape ecosystem was adopted to study the changes of landscapepattern from 1984 to 2004 in MYRDCW. In the past 20 years, sea area has always been the greatest class type, and it has been always expanding. The total area transformed from other wetland type to sea area has reached 2.72x10 ha, while the total area transformed to sea area from other types is only 0.45xl04ha. This is how serious the wetland loss is. Among all types, water area has changed the most, which reflects the massive changes resulted from development of tidal-flat aquiculture.The calculation of landscape pattern index indicates in the past 20 years the overall number of landscape patches has increased in MYRDCW. The landscape diversity has had some improvements but it is not remarkable. The level of fragmentation is not high. But the change trend of the regions is the number of patches increases; the index of mean area, mean nearest-neighbor distance and mean proximity decreases; landscape fragmentation gets more serious. Human activities contribute the most to the changes. The statistics of vegetation index indicate in MYRDCW, the area of vegetation coverage has decreased; wetland quality has worsened; coverage degree has decreased; and the overall vegetation coverage has become worse. This indicates that the degradation of the coastal wetland is obvious.Causes of degradation of MYRDCW include natural processes and human activities such as coastal erosion, sea level rise, storm surge, the break-flow of YR, development of oil field, tidal-flat reclaim, overfishing, construction of road and seawall, pollution, etc. The loss and degradation of MYRDCW is a complicated process. The influential factors are not working in an isolated fashion. The natural processes and human actions can not be separated completely. They work together to cause the constant changes of coastal wetland.The natural processes have created the base for MYRDCW. But human activities increase; development activities speed up; natural appearance changes remarkably; the quality of environment keeps declining; ecological structure is being destroyed; ecological function seriously declines; productivity decreases. Coastal wetland degradation started to happen and it's becoming worse and worse.This paper evaluates the degradation of MYRDCW by creating evaluation model with help of fuzzy mathematics methods. The evaluation results indicate that the degradation in the oil field area is the worst. It can be categorized as severe degradation. The degradation can be categorized as minor degradation in the newborn wetland nature reserve including the outfall area of YR and Yiqianer reserve. But due to the fact that they play an important role in MYRDCW, we can't really feel relieved with their level of degradation. As a whole, MYRDCW is in a state of minor degradation. But the degeneration is speeding up and is seriously threatening the health and safety of coastal wetland.Through field surveys, interpretation of RS images, analysis of data, it can be concluded that the degradation of MYRDCW will not stop in the near future and be a trend. It'll continue affecting the structure, function and value of the coastal wetland ecosystem.