Distinction of Driver Contributions to Wetland Decline and Their Associated Basin Hydrology Around Iran

Study region: Six wetland sites around Iran (Gavkhoni and Hur al-Azim wetlands, Gorgan Bay, and Namak, Urmia, and Maharloo & Bakhtegan lakes) and their associated hydrological basins. Study focus: The aim was to distinguish the contributions of climatic and non-climatic changes (including land-use/land-cover, LULC) to areal decline in six Iranian wetlands. This was done using data-driven quantification methodology that combined comparative change correlation and Budyko-based analyses of evapotranspiration (ETb), and runoff (Rb) changes in the hydrological basin of each wetland, extended to consider explicitly climate-driven change in evaporation rate (Ew) from the wetland area and the shift from previous Ew to ETb caused by the wetland decline itself. New hydrological insights for the region: Comparative correlation analysis revealed an overall stronger correlation of wetland decline with LULC changes (mainly cropland, urban land) than with changes in temperature (T) or precipitation (P) across all wetland sites. The extended Budyko-based analysis revealed that the predominant cause of wetland decline across all sites was increased ETb, with related decrease in Rb from basin to wetland, whereas changes in Ew and in wetland decline shifting Ew to ETb had only a weak influence. In line with the correlation analysis results, non-climatic drivers were revealed as causing ETb increases and Rb decreases, leading to wetland decline to a greater degree than climate change (T, P).