Analysis Of Risk Assessment And Evolution Of Zoige Plateau Marsh Wetland Degradation

Due to natural factors and human activities, more and more plateau wetlands have become degradated or even vanished, which has threatened the sustainable development of the environment and society. Therefore, the establishment of a reasonable risk assessment model to realize the wetland degradation assessment and its risk evolution analysis is of great significance to the rational development and utilization of the plateau wetlands, as well as to safe guarding regional ecological environment. In this paper, the author chose the Zoige Plateau Marsh Wetland as the research subject, and constructed a wetla nd degradation risk assessment model based on some natural factors and human threats in the internal side and the degradation of areas, constructions, as well as functions of the plateau wetlands in the internal side. By using the indexes of this model, the author made a degradation risk assessment of the Zoige Plateau Marsh Wetland, and analyzed the spatial distribution pattern of the risk and its evolution process with time and space changes. Research results are revealed as follows:(1) In this paper, nine indicators were selected, namely, drought index, human disturbance index, grazing intensity, area degradation rate, landscape fragmentation, landscape fractal dimension, water conservation function, biodiversity maintenance function, and wetland productivity, from the perspective of degradation stress degree and degradation degree, according to the Zoige Plateau Marsh Wetland condition, to calculate the degradation risk indexes from 2000 to 2014.(2) By comprehensively analyzing the degradation risk asse ssment results of the Zoige Plateau Marsh Wetland, main conclusions are made as follows: From time distribution, the degradation risk index increased by 26.69 %, ranging from 0.296 to 0.375, which turned the area a medium risk area from a low risk area dur ing the study period from 2000 to 2014. From spatial distribution, the juncture marsh wetland degradation risk index of Ma qu County, Zoige County, Aba County, Holocene County, was lower than that of other places, which were regarded as low risk areas. The relatively high and high risk areas were mainly distributed in Ma qu County and Zoige County, while the medium risk areas were mainly located around the surrounding marshes of the study area.(3) By contrastive analysis of the risk indexes of 2000, 2005, 2010 and 2014, risk index difference, risk level attitude and transition probability matrix were achieved. From risk index changes, the average index of the degradation risk in Zoige plateau marsh wetland was 0.0079 during 2000 and 2014, which meant that t he degradation risk of the marsh area was increased on a whole. But the risk of some areas was increased and the risk of some other areas was decreased on a local scale. From risk level difference, non-risk areas and medium risk areas were expanded among t he study area during 2000 and 2014, while high risk area remained almost the same, areas of other risk level reduced to some extent. The proportions of the areas changing from low risk areas to non-risk areas, lower risk areas and medium risk areas were 53.02 %、27.19 %、19.79 % respectively, while the proportions of the areas changing from lower risk areas to medium risk areas and relatively high risk areas were 78.42% and 21.58%.