Wetlands, those transitional lands between aquatic and terrestrial ecosystems, are vital for our planet, providing 40% of the world's ecosystem services. However, they cover only around 6% of the Earth's surface, and due to climate change and human intervention, they are at high risk of destruction or conversion. Iran, with its arid and semi-arid regions, is particularly susceptible to these changes, and its wetlands are facing significant challenges.
This study focuses on the aerosol dynamics and environmental drivers in Iran's lakes and wetlands over a 25-year period. It aims to analyze the trend of temporal changes in aerosol optical depth (AOD) and identify the factors influencing AOD variations. The findings reveal a general increasing tendency in AOD over Iranian lakes and wetlands, which is attributed to enhanced dust concentrations after lake desiccation due to climate change and human activities.
The study area includes 20 inland lakes and wetlands of international importance and 7 other significant water bodies. The results show that 8% of the water bodies experienced an increasing trend in AOD during the winter months, while 12% exhibited an increase in autumn. In spring and summer, despite an increasing trend in aerosol concentrations in more than half of the studied wetlands, the changes were not statistically significant.
Through the use of machine learning algorithms, the study identifies wind speed (WS) and enhanced vegetation index (EVI) as the main contributors to higher predicted aerosol concentrations in the Jazmourian Wetland. In the Parishan Wetland, normalized difference salinity index (NDSI) and normalized difference water index (NDWI) were found to be the most influential factors. The analysis also highlights that the influence of terrestrial factors on the predicted increasing trend of aerosols was approximately four times greater than that of climatic factors.
The implementation of three models (MLR, RF, and XGB) showed poor performance in predicting AOD over most water bodies, except for Jazmourian and Parishan, where they demonstrated acceptable performance. This suggests that the selected environmental variables may not fully explain the variations in AOD over these aquatic ecosystems. The study recommends future research to consider an expanded set of environmental drivers and conduct sensitivity analyses to enhance model accuracy and robustness.
The findings of this study emphasize the variety of factors affecting Iranian wetlands and the need for tailored actions to reduce air pollution and its adverse environmental effects. Continuous monitoring of air quality over aquatic ecosystems, especially wetlands experiencing an increasing trend of aerosols and water shrinkage, is crucial. International cooperation is also necessary to prevent further degradation of these valuable ecosystems.
