Spatiotemporal Monitoring of Changes in Mangrove Forest Cover and Chlorophyll-a Concentration in the Surrounding Waters of Mol-Gonzeh and Om-al-Gorm Island Using Satellite Data

Document Type : Original Article

Authors

1 Department of Environment, Faculty of Natural Resources, University of Zabol, Zabol, Iran.

2 Research Group of Biodiversity and Biosafety, Research Center for Environment and Sustainable Development (RCESD), Department of Environment, Tehran, Iran.

10.22091/ethc.2026.17001.1091

Abstract

Objective: Mangrove forests are valuable coastal ecosystems that play key ecological roles in coastal areas; therefore, long-term monitoring of these ecosystems is essential. This study aimed to investigate spatiotemporal changes in mangrove cover in Mol-Gonzeh and Om-al-Gorm Island, analyze transitions among water, bare soil, and mangrove classes, and assess trends in chlorophyll-a concentration.
Methods: Landsat satellite imagery available in Google Earth Engine was used to assess land-cover changes. Following preprocessing, the NDVI and NDWI indices were calculated, and the imagery was classified into three classes: water, bare soil, and mangrove. A time series of chlorophyll-a concentration in the surrounding waters was also estimated using an empirical model reported in previous studies. To reduce the effects of seasonal variability, tidal fluctuations, and cloud cover, images from 1986–1988, 1999–2001, and 2022–2024 were averaged and represented by 1987, 2000, and 2023, respectively. Change detection was performed using ENVI software.
Results: Mangrove forest area increased from 0.235 to 0.564 km², with the largest increase occurring between 2000 and 2023 (27.24 ha). Expansion mainly occurred through densification of existing patches in the eastern and northeastern parts of the study area. Overall classification accuracy was 90%, 89%, and 92%, respectively. Chlorophyll-a concentration ranged from 1.185 to 1.241 μg/L and showed an increasing trend from 2013 onward.
Conclusion: Mangrove cover increased while bare-soil areas decreased. The recent increase in chlorophyll-a may indicate changes in the surrounding waters; however, identifying the underlying drivers requires simultaneous assessment of environmental parameters and field validation.

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Main Subjects

References

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