Extended Abstract
Introduction: Today, due to human activities, climate change, and other factors, wetlands within the country are rapidly diminishing. Wetlands are critical ecosystems that support a vast array of biodiversity and provide valuable goods and services. They offer numerous economic and environmental advantages, such as carbon sequestration, groundwater replenishment, flood mitigation, and resources for food and fodder. Globally, wetlands are subjected to intense degradation pressures, primarily due to human-induced changes. These include expanding agriculture, urban development, inter-basin water transfers, and destroying natural habitats. Additionally, alterations in wetland catchment areas, resulting from land use changes that affect various surface processes, typically modify the condition of wetlands. Consequently, this study aims to examine the transformation of the Salehiyeh wetland from 1987 to 2023 using Landsat satellite imagery and to explore the factors contributing to the area's degradation and desertification through documentary and field surveys.
Materials and methods: Landsat 5 and 8 satellite images were utilized to study the changes in water bodies and saltlands in the Qazvin-Alborz region from 1988 to 2023. Following radiometric and atmospheric corrections, maps depicting the region's water bodies and vegetation cover were generated using ArcGIS Pro 2.8 and ArcGIS 10.8, respectively. These maps were derived using the Modified Normalized Difference Water Index (MNDWI) and the Normalized Difference Vegetation Index (NDVI) for the years of study. Documentary research and survey methods also identified the primary factors influencing these changes.
Results and Discussion: The results indicated that the water abstraction area in the study area was approximately 8922.36,2844.02 and 1135.28 hectares in 1988, 1998, and 2009, respectively. This area decreased to 921.01, 409.38, and 167.54 hectares in 2019, 2022, and 2023, respectively. Correspondingly, the changes in the area's vegetation were consistent with the changes in its water. Before the construction of the drainage system, in 1988, 1998, and 2009, vegetation covered approximately 7196.56, 4293.62, and 2576.50 hectares, respectively. In the years following the construction of the drainage system, namely 2019, 2022, and 2023, the vegetation spanned 3337.12, 514.64, and 473.61 hectares, respectively. Investigations revealed that disruptions in the wetland's hydrological cycle due to the construction of dams on the main rivers, the development of drainage systems, communication lines, infrastructure, and the pressure of livestock grazing are the most significant factors affecting the current condition of the wetland. The results related to explaining the key drivers of desertification and land degradation in the Salehiyeh wetland and the saltland of the central Qazvin plain have shown the serious impact of human activities on the current state of the wetland. In the meantime, the loss of wetland rights due to the construction of Kinehwors Dam on the Abharroud River, the construction of a diversion dam on the Kordan River to Hashtgerd Plain recharge, and the construction of a diversion dam on the Ziyaran River played an important role in disrupting the hydrological cycle of the wetland. The implementation of construction projects in the wetland, including the construction of a drainage system, the construction of the Abyek-Charamshahr freeway, the establishment of Azadi Airport, and the development of agricultural lands, has contributed to the cause of a serious threat to the safety of the wetland's wildlife, its destruction, and its ecological and geographical isolation. Also, constructing the access road and overpasses to transfer water on the side and the drainage canal has provided more access to the herdsmen and hunters. It has increased the population of excess grazing animals in that area, especially camels.
Conclusion: Generally, the desertification and land degradation observed in the Salehiyeh wetland and the salt lands of the central Qazvin plain can be attributed to a neglect of sustainable land management principles. Additionally, climatic anomalies have exacerbated the destructive effects over the past two decades. Any measures aimed at correcting and enhancing the ecological condition of the wetland should prioritize controlling the primary sources of dust production. These measures should involve mitigating the impact of human activities as much as possible, regulating livestock grazing, restoring vegetation, and emphasizing organizational unity and the involvement of local communities.