Monitoring of 35-Year Mangrove Wetland Change Dynamics and Agents in the Sundarbans Using Temporal Consistency Checking

Abstract

Mangrove wetlands are rapidly being lost due to anthropogenic disturbances and natural processes, such as sea-level rise (SLR), but are also recovering as a result of conservation efforts. Accurate and contemporary mangrove maps to detect their distribution and changes are urgently needed to understand how mangroves respond to global change and develop effective conservation projects. Here, we developed a new change detection algorithm called temporal consistency checking combining annual classification and spectral time series (TCC-CS) for tracking mangrove losses and gains. Specifically, mangrove change events were determined by measuring the deviation of greenness and wetness of candidate change segments from automatically collected mangrove reference samples. By applying to the world’s largest mangrove patches, we monitored the 35-year mangrove trajectory in the Sundarbans from 1988 to 2022 using all available Landsat images on the Google Earth Engine platform. In the Sundarbans, 18,501.89 ha of mangroves have been gained, but these have been offset by losses of 27,009.79 ha, leading to a net mangrove loss of 1.42% (8507.9 ha) in the past 35 years. We further mapped the pixel-level change agents and found that SLR-induced erosion and degradation, instead of human activities, were the major drivers of losses in the Sundarbans. Trend analysis on loss agents indicates that mangrove losses caused by human activities, such as the expansion of croplands and aquaculture ponds, have declined, but SLR is still a persistent threat to mangrove wetlands in this iconic mangrove area. Our study provides a computationally efficient methodology for examining large-scale mangrove changes, and the resultant annual mangrove maps provide strong support for mangrove conservation in the Sundarbans.

Editorial for Special Issue: “Monitoring Terrestrial Water Resource Using Multiple Satellite Sensors”

“…Sun et al [33] used multi-temporal Landsat imagery to obtain the lake shoreline of Hulun Lake in various years to further estimate lake water storage changes and analyze water balance. Zhang et al [34] conducted monitoring of mangrove wetland change dynamics across the Sundarbans using all available Landsat image time series on the Google Earth Engine platform, and observed a net mangrove loss of 8507.9 ha from 1988 to 2022.…”

MangroveSeg: Deep-Supervision-Guided Feature Aggregation Network for Mangrove Detection and Segmentation in Satellite Images

“…Mangrove forests can be found mainly in the southeast, south coasts, and bays with silt deposits in China [1,2]. The mangrove ecosystem supports an incredible diversity of creatures, including some species that are unique to mangrove forests and extremely important to the coastal ecosystems they inhabit [3][4][5][6][7]. Physically, mangrove forests improve water quality by filtering pollutants, mitigate climate change by storing carbon, reduce coastal erosion, and act as a buffer zone between marine and terrestrial communities, protecting coastlines from damaging floods, waves, and winds.…”

Mangrove Health: A Review of Functions, Threats, and Challenges Associated with Mangrove Management Practices

“…Around 75% of the total mangrove population is concentrated in 15 countries [27], of which only 6.9% thrive in protected areas [28]. The majority of mangroves exist in the Southeast Asian region, particularly in Indonesia, Malaysia, and Myanmar [29].…”