تجزیه‌وتحلیل نقش فعالیت‌های زراعی در تخریب میراث ژئومورفوسایت‌ها مطالعه موردی: ریگ اکبرآباد، استان خراسان جنوبی

ABSTRACT
Among the major environmental challenges confronting the global community, desertification remains one of the most pressing. Aeolian landforms, recognized as significant geomorphosites, constitute valuable natural heritage resources that are widely used for scientific, educational, and tourism purposes. However, these landforms are highly vulnerable to human-induced degradation, which highlights the necessity of effective protection and management measures. The Rig-e Akbar Abad, located along the southern margin of the Mokhtaran Plain, represents one of the most prominent geomorphological manifestations of aeolian erosion in the region. In recent decades, intensified agricultural expansion accompanied by infrastructure development has increasingly threatened this aeolian geomorphosite. This study employed Landsat satellite imagery at ten-year intervals to assess changes in land use and vegetation cover. Following image preprocessing, land cover and land use were classified using a supervised classification approach, and the Normalized Difference Vegetation Index (NDVI) was calculated. Spatiotemporal variations within the geomorphosite were analyzed through the overlay of land-use maps from different time periods. The results indicate a substantial increase in agricultural land use accompanied by a noticeable decline in average NDVI values, suggesting intensified drought conditions. Spatial analysis further reveals that agricultural activities have gradually expanded from the dagh margins toward more distant areas, encroaching upon the sand dune system. Currently, approximately 7.87% of the Rig-e Akbar Abad area is under agricultural use, predominantly associated with irrigated farming. These findings highlight the increasing anthropogenic pressures on aeolian geomorphosites and underscore the urgent need for sustainable land management and conservation strategies in arid environments.
Extended Abstract
Introduction
Among contemporary global environmental challenges, desertification is widely regarded as one of the most significant threats. Within this context, geomorphosites, particularly those formed through aeolian processes, represent some of the most important expressions of natural heritage and geotourism in arid and semi-arid regions. In addition to their scientific and educational value, these geosites play a fundamental role in sustainable tourism development; however, they face serious threats arising from human exploitation. This research examines Rig-e Akbar Abad, one of the most significant manifestations of wind erosion in the southern part of South Khorasan Province, as a case study of a sensitive and fragile geomorphological heritage site, with the aim of analyzing the impact of expanding agricultural activities on the degradation and land-use changes of this geomorphosite.
 
Methodology
The research methodology is based on remote sensing techniques and spatial analysis conducted within a GIS environment. For this purpose, Landsat satellite imagery from two time points at a ten-year interval, namely 2010 and 2020, was utilized. Following the necessary preprocessing steps, including geometric and radiometric corrections, land use and land cover (LULC) maps and the Normalized Difference Vegetation Index (NDVI) were generated and compared for both periods. In addition to remote sensing data, statistical and field-based information was used, including reports from the Ministry of Agriculture, statistical yearbooks, and meteorological data such as temperature, precipitation, and wind. Data analysis was conducted using statistical tests, including the t-test, Pearson correlation, and chi-square test, implemented in ArcGIS, ERDAS IMAGINE, and Minitab software, in order to determine the relationships between changes in vegetation cover, drought conditions, and the expansion of agricultural land use in the vicinity of the rig.
Results and discussion
From a geomorphological perspective, the Rig-e Akbar Abad consists of four main sand dune units covering a total area of approximately 3,099.6 hectares. These dunes are predominantly young and active and include forms such as incomplete barchans, pyramidal dunes, and transverse dunes, which are partially stabilized by native vegetation including Calligonum, Alhagi, and Stipa agrostis. However, the conversion of these lands into farmland has disrupted their natural dynamics and poses a serious threat to their geomorphological stability. The expansion of agricultural development around the dagh, particularly in the southern parts of the plain, has disturbed the balance between natural aeolian and erosional processes, leading to the conversion of parts of the flat sand sheets into temporary farmlands.
Within the rig area, 87.7% of the total surface experienced a decrease in NDVI values, indicating a substantial decline in vegetation cover, while only 0.06% of the land remained pristine and unchanged. Concurrently, an increase of approximately 39.69% in irrigated lands and a decrease of 7.87% in active sandy areas were observed. This trend reflects the gradual conversion of sandy surfaces into agricultural land, partly driven by the overexploitation of groundwater resources. According to official statistics, the number of authorized and unauthorized wells in the region increased from 131 in 2002 to more than 250 in 2021, which has played a major role in the expansion of irrigated agriculture despite intensifying drought conditions.
Accuracy assessment of the land use classification, based on 150 field samples and an error matrix, yielded an overall accuracy of 86.89% and a Kappa coefficient of 0.799, indicating a high level of analytical reliability. These findings confirm that unbalanced agricultural development, which disregards environmental and climatic capacities, has resulted in a reduction in geomorphological diversity and the loss of some unique characteristics of the geosite.
The results indicate significant transformations in the spatial structure and ecological conditions of the Rig-e Akbar Abad geomorphosite during the study period. A significant decrease in NDVI values reflects a decline in vegetation cover and the intensification of drought conditions in the region. Spatial analysis of land use changes revealed that agricultural lands, particularly irrigated farming areas, increased at an annual rate of approximately 3.57%. In 2010, approximately 18.45% of the study area was allocated to agricultural use, whereas this proportion increased to more than 30.24% by 2020. The expansion of irrigated lands, particularly around the dagh margins and the southern parts of the rig, coincided with a 26.95% decrease in dagh areas and an 8.7% reduction in sand dune areas. The results of the chi-square test confirm that these changes are statistically significant at the α ≥ 0.05 level.
The overall findings of the study indicate that the uncontrolled expansion of agricultural activities and the unsustainable exploitation of groundwater resources are the primary factors contributing to the degradation of the Rig-e Akbar Abad geomorphosite. The expansion of irrigated farmlands, the reduction of rain-fed lands, and the significant decline in NDVI values, together with increasing drought, have transformed the environmental structure of the region. The Rig-e Akbar Abad, which could be promoted as one of the most significant geotourism attractions in eastern Iran within a sustainable development framework, now faces the risk of gradual degradation. The continuation of this trend will not only lead to the loss of valuable natural heritage but also result in the destabilization of the aeolian ecosystem and the intensification of soil erosion at the local scale.
 
Conclusion
It is necessary to formulate management policies aimed at the conservation and restoration of geomorphosites. These policies should include restrictions on land-use change in sandy areas, the regulation of water resource exploitation, the promotion of sustainable agriculture through low-consumption methods, and strategic planning for the geotouristic utilization of the Rig-e Akbar Abad. Furthermore, educating local communities and raising awareness of the scientific and economic values of geomorphological heritage can play a significant role in preventing further degradation.
 
Funding
There is no funding support.
 
Authors’ Contribution
Authors contributed equally to the conceptualization and writing of the article. All of the authors approved thecontent of the manuscript and agreed on all aspects of the work declaration of competing interest none.
 
Conflict of Interest
Authors declared no conflict of interest.
 
Acknowledgments
We are grateful to all the scientific consultants of this paper.