The Risk Assessment Of The Impact Of Climate Change On Desertification In Yellow River Irrigation District Of Ningxia

For a long time,climate change and desertification prevention and control have been closely followed and discussed by the human society.The results of the Fourth National Desert Land Survey and Survey(2014)showed that China's 2.622 million square kilometers of land have been suffering by desertification.With the impact of the desertification of about 400 million people in China,the direct economic loss caused by desertification has reached 54.1 billion yuan.The prevention and evaluation of desertification is imminent.Understanding the formation and evolution mechanisms of desertification in recent decades,the relationship between climate change and desertification,and the prediction of possible development status of desertification within a certain time scale in the future will be of great significance for the mitigation measures for desertification.For this purpose,Yellow River Irrigation District of Ningxia(mainly including the Yinchuan Plain and Zhongwei Basin)was selected as typical research areas for desertification.Based on the 3S technology,it will observe the temporal and spatial changes of desertification in the research area in the past 40 years and assess the climate factors.The level of impact on desertification,based on desertification characterization data and climatic factors data for the past 30 years,predicts desertification risks that may result from climate change under different climate scenarios in the next 30 years.The following main conclusions are drawn:(1)Over the past 40 years,the desertification situation in the Ningxia Yellow River Irrigation Area has improved as a whole.In general,the desertification area has gradually decreased,and the non-desertification area has increased.From 1975 to 1985,the desertification land was reversed,and the rate of reverse rotation was-128.92km2/10 a.From 1985 to 1995,the area of desertified land increased,and the rate of change was 257.95km2/10 a.In 1995-2005,the desertification land reversed again,and the reversal intensity was significantly increased.The increase was-1006.3km2/10a;the area of desertified land increased from 2005 to 2015,and the rate of change was 79.11km2/10 a,but overall the area of desertification in 1975 and 1985 was still improving.The overall reversal of desertification during 1995-2005 has been the strongest in the past 40 years.Severely desertified land had the largest area reduction during 1985-1995,which was-71.37km2/10 a.However,it rebounded and developed 193.4km2 in 1995-2005,and continued to grow during 2005-2015.According to the differences in the degree of desertification within the study area,it was concluded that the overall desertification grades in the Ningxia Yellow River Irrigation Area are high,most of the moderate and severe desertification are located in the periphery of the study area,due to the irrigation by Yellow River,the desertification grade of internal areas is low.(2)Analyzing the characteristics of climate change in Ningxia Yellow River Irrigation District in the past 30 years,the annual accumulated temperature in the study area has maintained an overall upward trend,Yinchuan Plain has increased more than Zhongwei Basin,and the distribution of annual precipitation changes has a high similarity with regional vegetation coverage.The precipitation in Yinchuan plain with low degree of desertification is significantly higher than that in the Zhongwei basin.Compared with the annual accumulated temperature and annual precipitation changes,the overall average annual wind speed change is very small,which has little impact on the occurrence and development of desertification.According to the correlation analysis of annual accumulated temperature,annual precipitation,and average annual wind speed,these three climate elements and NDVI,on the 30-year scale,in addition to the annual accumulated temperature,the annual precipitation and the annual average wind speed and NDVI are less relevant.However,the correlation is higher at the 10-year scale.(3)In the next 30 years,under different climate change scenarios,the spatial distribution of desertification risk in Ningxia Yellow River Irrigation Area will be different: the area without risk of desertification will be at a higher level under RCP2.6 scenario,and RCP2.6 and RCP4.5 show a high degree of similarity,the land area with high-risk desertification reached the maximum value under the RCP4.5 scenario.In the RCP8.5 climate scenario,the desertification area of each risk level was intermediate between other climate scenarios.