Assessing the changes of mangrove ecosystem services value in the Pars Special Economic Energy Zone

The Pars Special Economic Energy Zone (PSEEZ) is the largest global special economic zone in the field of oil, gas, and petrochemical industry. The Nayband national marine park is located in the PSEEZ and mangrove forests are spread throughout the estuaries (Bidkhun or Asaloyeh, Basatin and Haleh) of the park. Despite important goods and ecosystem services of mangroves and their high economic value, mangroves within the PSEEZ are threatened by activities of the oil industry. Thus, it is necessary to monitor and assess the mangroves and their ecosystem services. In this context, remote sensing technologies provide effective tools for spatio-temporal analysis of mangrove distribution. In this study, Landsat-5, 7, 8 images were used from 1986 to 2018. Support Vector Machine (SVM) and Sen's slope was employed for monitoring mangrove cover changes and estimating Normalized Difference Vegetation Index (NDVI) trends. In assessing the economic value of the ecosystem services of the Mangrove forests, the mangrove distribution changes and global values of mangrove ecosystem services were integrated. The results revealed that the coverage of mangroves had increased to about nearly 204.93 ha in area from 1986 to 2003, followed by a drop to 169.29 ha in 2018. The economic value of mangrove forests of the PSEEZ in 1986, 1998, 2003, 2015 and 2018 was estimated to be about 3.3, 3.8, 6.7, 6.5 and 5.5 million US dollars per year, respectively. Based on Sen's slope, the NDVI trend in Basatin estuary decreased at a rate of - 0.001, but showed significant increases of about 0.008 and 0.006 for the Bidkhun and the Haleh estuaries, respectively. Despite the suitable distribution and an economic value of $1.9 million in 1986, conditions of the Basatin estuary seem to have diminished from 1986 to 2018 (economic value of $0.71 million in 2018). The Bidkhun estuary, which showed a positive trend in distribution changes, has also been downgrading since 2015 to about 30.43 ha in size, and an economic value of $1 million. Since 1998, the mangroves of Haleh estuary have been improving distribution-wise, with further elevations in economic value ($ 0.26 million in 2018).