Analysis of land use/cover changes using the concepts of ecosystem services for the ecological security assessment of Lavasanat watershed (Tehran, Iran)

Abstract Recent years have seen growing interest in the use of the concepts of ecosystem services in ecological security assessments. This study analyzed the temporal-spatial changes of land use/cover in Lavasanat watershed, Tehran, Iran, between the years 2000 and 2040 under different land-use change scenarios, and assessed the consequent change in ecological security in terms of ecosystem services (water yield) under different climate scenarios. First, the LULC map of the watershed for the 20 year period between 2000 and 2020 was generated. Then, the area’s LULC changes from 2020 to 2040 were predicted based on the assumption of the continuation of current conditions, which was named Scenario S1. Next, three other scenarios named S2, S3, and S4, representing the pessimistic, realistic, and optimistic management of the situation were defined based on S1. Three climate scenarios named B1, N and M were also defined for use in the assessments. For ecological security assessments, temporal and spatial changes of water yield services for the years 2000, 2010 and 2020 were simulated based on the area’s climate data and LULC changes. The results were then used to estimate the water yield of the entire watershed and its residential areas by 2040 in the four defined land-use/cover scenarios (S1, S2, S3, and S4) and three climate scenarios (B1, N, and M). The results showed a 1.92 times increase in the water yield of the watershed’s residential areas from 2000 to 2020. Among the scenarios defined for Lavasanat watershed, the worst scenario (with the highest water yield) was S2N with a water yield of 37639293.581m 3 in the entire watershed and 35091082.311m 3 in the residential areas, and the best scenario (with the lowest water yield) was S4M with a water yield of 8329365.079m 3 in the entire watershed and 7353006.022m 3 in the residential areas. The results of all of the four land-use/cover scenarios under all three climate scenarios showed an increase in water yield, the expansion of residential areas, and the loss of ecologically valuable lands in the watershed by 2040.