Changes in land use and ecosystem services at Sahand Dam using remote sensing technique

Recently, land use change is one of the main potential causes in losing biodiversity and ecosystem services. Dams as main human-made structures play an important role in saving surface water. Due to the rapid increase in dam construction over the last 40 years in Iran, the contradiction between dam productivity and the loss of ecosystem services has become an issue of increasing concern. The aim of this study was to investigate the impact of Sahand Dam construction on land use, land use changes and ecosystem services. In this study three Landsat satellite images were used to track land use changes over a period of 28 years (1989, 2006 and 2017). First, these images were used for geometric, atmospheric and topographic correction. The maximum possibility of different land uses and cover were determined using a supervised classification method and their accuracy was checked again by field inspection. The user authenticity and Kappa coefficient calculated and resulted in value of 63 and 79 percent respectively. The value of ecosystem services and changes in land uses carried out using aerial photographs and satellite imagery between 1989 and 2017 throughout 49400 ha of areas around Sahand Dam in East Azarbaijan Province. The results showed that the total area for rangeland decreased significantly between years 1989 and 2017 while there has been a noticeable increase in cropping land. In general, the share of area under rangeland decreased by 56% over period 1989-2017. The total area for rainfed and irrigated cropping areas increased by 38 and 32 percent, respectively, indicating significant changes in this area. As regards to the services of ecosystem value, land use changes from rangeland to crop land led to a 35900000 dollars annually loss in ecosystem services value ($10.6 per hectare per year). To conclude, although dam construction and shifting from natural land toward crop land may be profitable but due to the depletion of the ecosystem capacities to deliver ecosystem services, long-term losses may exceed short-term gains. Land use and policy-making should aim at balancing society needs and preferences, while considering the long-term negative effects of dams and ecosystem service losses. Therefore, providing a land management roadmap for future economic development programs is now receiving a great priority. It will be beneficial if natural ecosystems are preserved and used adequately.