Your search found 2 records
1 Bunting, P.; Rosenqvist, A.; Lucas, R. M.; Rebelo, Lisa-Maria; Thomas, N.; Hardy, A.; Itoh, T.; Shimada, M.; Finlayson, C. M. 2018. The global mangrove watch - a New 2010 global baseline of mangrove extent. Remote Sensing, 10(10):1-19. [doi: https://doi.org/10.3390/rs10101669]
Mangroves ; Wetlands ; Mapping ; Landsat ; Satellite imagery ; Satellite observation ; Earth observation satellites ; Human behaviour ; Coastal area ; Deltas ; Environmental monitoring
(Location: IWMI HQ Call no: e-copy only Record No: H049127)
(18 MB)
This study presents a new global baseline of mangrove extent for 2010 and has been released as the first output of the Global Mangrove Watch (GMW) initiative. This is the first study to apply a globally consistent and automated method for mapping mangroves, identifying a global extent of 137,600 km 2 . The overall accuracy for mangrove extent was 94.0% with a 99% likelihood that the true value is between 93.6–94.5%, using 53,878 accuracy points across 20 sites distributed globally. Using the geographic regions of the Ramsar Convention on Wetlands, Asia has the highest proportion of mangroves with 38.7% of the global total, while Latin America and the Caribbean have 20.3%, Africa has 20.0%, Oceania has 11.9%, North America has 8.4% and the European Overseas Territories have 0.7%. The methodology developed is primarily based on the classification of ALOS PALSAR and Landsat sensor data, where a habitat mask was first generated, within which the classification of mangrove was undertaken using the Extremely Randomized Trees classifier. This new globally consistent baseline will also form the basis of a mangrove monitoring system using JAXA JERS-1 SAR, ALOS PALSAR and ALOS-2 PALSAR-2 radar data to assess mangrove change from 1996 to the present. However, when using the product, users should note that a minimum mapping unit of 1 ha is recommended and that the error increases in regions of disturbance and where narrow strips or smaller fragmented areas of mangroves are present. Artefacts due to cloud cover and the Landsat-7 SLC-off error are also present in some areas, particularly regions of West Africa due to the lack of Landsat-5 data and persistence cloud cover. In the future, consideration will be given to the production of a new global baseline based on 10 m Sentinel-2 composites.
2 Bunting, P.; Rosenqvist, A.; Hilarides, L.; Lucas, R. M.; Thomas, N.; Tadono, T.; Worthington, T. A.; Spalding, M.; Murray, N. J.; Rebelo, Lisa-Maria. 2022. Global mangrove extent change 1996–2020: Global Mangrove Watch version 3.0. Remote Sensing, 14(15):3657. (Special issue: Advances in Remote Sensing of Land-Sea Ecosystems) [doi: https://doi.org/10.3390/rs14153657]
Mangroves ; Ecosystems ; Datasets ; Coastal erosion ; Time series analysis ; Estimation ; Landsat ; Satellite imagery ; SAR (radar) ; Observation ; Mapping
(Location: IWMI HQ Call no: e-copy only Record No: H051368)
https://www.mdpi.com/2072-4292/14/15/3657/pdf?version=1660028312
https://vlibrary.iwmi.org/pdf/H051368.pdf
https://vlibrary.iwmi.org/pdf/H051368.pdf
(12.00 MB) (12.0 MB)
Mangroves are a globally important ecosystem that provides a wide range of ecosystem system services, such as carbon capture and storage, coastal protection and fisheries enhancement. Mangroves have significantly reduced in global extent over the last 50 years, primarily as a result of deforestation caused by the expansion of agriculture and aquaculture in coastal environments. However, a limited number of studies have attempted to estimate changes in global mangrove extent, particularly into the 1990s, despite much of the loss in mangrove extent occurring pre-2000. This study has used L-band Synthetic Aperture Radar (SAR) global mosaic datasets from the Japan Aerospace Exploration Agency (JAXA) for 11 epochs from 1996 to 2020 to develop a long-term time-series of global mangrove extent and change. The study used a map-to-image approach to change detection where the baseline map (GMW v2.5) was updated using thresholding and a contextual mangrove change mask. This approach was applied between all image-date pairs producing 10 maps for each epoch, which were summarised to produce the global mangrove time-series. The resulting mangrove extent maps had an estimated accuracy of 87.4% (95th conf. int.: 86.2–88.6%), although the accuracies of the individual gain and loss change classes were lower at 58.1% (52.4–63.9%) and 60.6% (56.1–64.8%), respectively. Sources of error included misregistration in the SAR mosaic datasets, which could only be partially corrected for, but also confusion in fragmented areas of mangroves, such as around aquaculture ponds. Overall, 152,604 km2 (133,996–176,910) of mangroves were identified for 1996, with this decreasing by -5245 km2 (-13,587–1444) resulting in a total extent of 147,359 km2 (127,925–168,895) in 2020, and representing an estimated loss of 3.4% over the 24-year time period. The Global Mangrove Watch Version 3.0 represents the most comprehensive record of global mangrove change achieved to date and is expected to support a wide range of activities, including the ongoing monitoring of the global coastal environment, defining and assessments of progress toward conservation targets, protected area planning and risk assessments of mangrove ecosystems worldwide.
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