Assessment of Areas Susceptible to Desertification with Emphasis on Erosion Models Using Multi-Criteria Decision Analysis A Case Study (Sistan Suture Zone and Afghan Blocks)

ABSTRACT

Introduction: Desertification is one of the major challenges of today's world, threatening environmental sustainability. This phenomenon arises from land degradation in arid and semi-arid regions and can have serious consequences for the environment, economy, and society. Due to its geographic location in the dry and semi-arid belt of the world, Iran is at risk of desertification. To combat this phenomenon, it is essential to identify and assess the influential factors, determine vulnerable areas, and use models to evaluate this issue. The use of remote sensing technologies and Geographic Information Systems (GIS) can be beneficial in assessing and monitoring desertification. These technologies enable comprehensive and accurate examination of land cover changes and assist in the management and protection of at-risk areas. This study aims to identify areas susceptible to desertification in the eastern belt of Iran (Sistan Suture Zone and Afghan Blocks) using multi-criteria decision analysis models based on the Ordered Preferential Approach (OPA).

Materials and methods: The geological zone of Sistan and the Afghan Blocks, covering an area of over 106,000 square kilometers, is located in the eastern belt of Iran and includes parts of Sistan and Baluchestan and South Khorasan provinces. According to the De Martonne climate classification, this area falls within the arid and hyper-arid climate zones. Such conditions, along with vegetation degradation and the drying up of water resources, have made this region susceptible to desertification. In this study, to obtain a map of areas prone to desertification, wind and water erosion potential maps were first generated using the RWEQ and RUSLE models, respectively, in the study area. The results of these models, along with other indicators such as vegetation cover, soil salinity, land use, temperature, soil classification, bulk density, and climate classification, were weighted using a multi-criteria decision analysis model based on the Ordered Preferential Approach (OPA). Finally, a map of areas susceptible to desertification in the eastern belt of Iran was produced.

Results: The results of this study showed that the average wind erosion potential in the eastern belt of Iran is 64 kg per square meter. Notably, 16% of this area, primarily located in the eastern and southeastern parts, including the cities of Zabol, Saravan, and Khash, has a wind erosion potential exceeding 512 kg per square meter. In contrast, the average water erosion was found to be 24.36 tons per hectare, with the highest rates of water erosion exceeding 40 tons per hectare covering 34.5% of the study area, primarily in the northern region, including the city of Nehbandan in South Khorasan province and central parts of the area. Finally, the results of the multi-criteria decision analysis model based on the Ordered Preferential Approach indicated that the most significant factors identified by experts in recognizing areas susceptible to desertification in this region are wind erosion, vegetation cover, and soil salinity. The eastern and southeastern parts of the area are severely affected by desertification.

Conclusion: Erosion in the eastern belt of Iran has multiple negative consequences, including reduced soil fertility and threats to livelihoods, food security, and public health. The degradation of vegetation, loss of water resources, and conversion of these areas into barren lands, particularly in the eastern half of Iran, which has faced extensive drought in recent years, have had the most significant impact on desertification. To deal with this problem, there is a need for management such as resource management, sustainable agricultural development and biodiversity conservation. These initiatives should be designed and implemented considering the specific conditions of each region and with the participation of local communities and experts. The results of this study indicate that the use of models based on the Ordered Preferential Approach can be effective in identifying vulnerable areas for the formulation of effective management plans. Additionally, incorporating indicators such as grazing management, population, and groundwater levels in future studies will facilitate a better assessment of desertification status.