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Abstract:  
 Introduction
The growing trend of desertification is one of the most serious environmental, economic and social problems in Iran. To recognize desertification processes and their causes and intensification is important and necessary that should be studied and evaluated. Therefore, it is necessary to select criteria and indicators in order to provide a model to show the intensity of desertification and determine the most important factors Impressive on desertification to prevent the Expansion of desertification factors. Due to the dry climate, low rainfall, unfavorable soil conditions, unprincipled land use change and increased wind erosion, Sarakhs has faced desertification crisis conditions and has created environmental problems as the center of wind erosion crisis. Due to the severe environmental and human problems and the strategic position of Sarakhs, the present study was conducted to assess the severity of the risk using the Iranian model IMDPA and to calculate and prepare a desertification risk map in the region. In this study, all the criteria of the mentioned model were evaluated. Desertification risk maps and the effective indicators of desertification in the region serve as a suitable and efficient tool for managing desertification crises. According to this, the prioritization of the crisis management program as well as the type of programs will be determined.
 
Methodology
To assess the severity of desertification, the Iranian IMDPA method and the geometric mean of the nine climatic criteria, geology, vegetation, agriculture, water, soil, water and wind erosion, social and economic issues, urban and industrial development were used. The scoring of criteria and indicators was performed in work units, which are the faces of subsistence. Risk assessment of desertification was achieved by combining the risk map of desertification risk, hazardous elements and the degree of environmental vulnerability using global risk equation.  After identifying the desertification risk classes and identifying the natural and human elements across the risk classes, using the expert opinions and field facts, the vulnerability classes of the elements, according to the type of class the severity of the risk was determined. To calculate the quantitative value of environmental vulnerability, the hazard map and the conditions of each element were considered economically and ecologically. Elements at higher risk will also be more vulnerable. This evaluation is based on the opinions of the experts of the relevant executive departments and according to the regional conditions, which can have different values ​​in different regions. Finally, the product of the risk classes of desertification (H) in the classes of hazardous elements (E) and the degree of vulnerability of the elements (V) in the GIS environment of the risk classes (R) were determined.
 
Results
In order to achieve the map of work units, lithographic maps, physiography, land use, satellite images were prepared and interwoven in the GIS environment. After combining the maps in the ArcGIS geographic information system environments, version 10/2, work units were obtained to review and correct, in addition to locating on Google Earth images of land use maps, geology, surface cover maps to further adapt to landforms. Used. Finally, in the study area, 3 units, 22 brigades and 67 geo-biophysical faces were separated. The numerical value of each of the faces, based on the geometric mean of the criteria and characteristics of desertification in the IMDPA model, was estimated to be 3, which indicates the intensity of severe desertification in the region. In terms of zoning, the region was classified into four lower classes with an abundance rate of 0.6, medium with an abundance rate of 18.8, severe with an abundance rate of 6.9 and very intense with an abundance percentage of 11.7. Among the effective factors, wind erosion criteria, vegetation cover, agriculture and socio-economic, all four criteria with an average weight of 3.5 had the greatest impact on the intensity of desertification in the region. The vulnerability and sensitivity of the phenomena showed that more than 35% of the area of ​​the elements with low sensitivity and more than 64% are in the middle class. Using global risk equation number of risks was calculated and classified into four categories, low to high, which have a frequency of 11.97%, 26.53%, 46.24% and 15.26%, respectively. More than 60 percent of the region in the west and east of the Sarakhs region is on the high and very high level in terms of risk and desertification. These areas are home to many agricultural lands.
 
Discussion & Conclusions
Based on the results, it was found that more than 80% of the study area in the whole area is in the classification of severe and very severe desertification, and among the studied criteria, the criterion of wind erosion, vegetation, agriculture and socio-economic value with weight value 3.5 has had the greatest impact on the regionchr(chr(chr('39')39chr('39'))39chr(chr('39')39chr('39')))s desertification process. In general, the use of IMDPA model as an Iranian model and compatible with Iranchr(chr(chr('39')39chr('39'))39chr(chr('39')39chr('39')))s climatic and environmental conditions, especially the study area, has been able to provide a good assessment of the intensity of desertification in the region. Also, the application of the global risk model, due to the use of intensity maps, hazardous elements and environmental vulnerabilities, has indicated the possibility of desertification development in the region. Evaluation of hazardous elements, especially human and economic elements, is a good practice to assess environmental vulnerabilities, which in this study was tried to be used properly. Desertification intensity map alone cannot be a useful tool for providing a desert crisis management program. The region may be in a highly desertified state, but due to the lack of endangered elements, the risk of desertification is not significant and is not a priority in the Desert Crisis Management Program. So in addition to the map of desertification intensity, the map of endangered and vulnerable elements is also important. This research is innovative as an applied research due to the assessment of the intensity and risk of desertification.
     
Type of Study: Research | Subject: Desert
Received: 2020/08/28 | Accepted: 2020/12/18